The prevention of prostate cancer has just begun to be studied. At the microscopic level, men throughout the world appear to have the early stage of the disease. However, the large variations in the progression of the disease among populations in particular regions are the focus of researchers. For example, Asians who move to the United States have a higher incidence of prostate cancer than those who live in Asia. This suggests a role for nutrition in the prevention of the disease. Animal fats and certain vegetable oils appear to be critical factors in disease development. Diets that involve the ingestion of large amounts of fresh fruits and dark-colored vegetables have been shown, in general, to have cancer-prevention effects.
Phytonutrients
Even though there is evidence that supplementation of various nutrients to the diet can provide benefits in the prevention and therapy of prostate cancer, more benefit may be derived from obtaining various nutrients from natural sources in the diet. In fact, the National Cancer Institute recommends the ingestion of at least five servings daily of fruits and vegetables to fight the development and progression of prostate cancer.
In addition, scientists have discovered that not all nutrients have been identified in some foods. The phytochemicals known as silymarin, genistein, and epigallocatechin 3-gallate have been shown to inhibit prostate cancer cells from multiplying. Several studies have found that vegetables, fruits, and whole grains contain numerous phytonutrients that modulate cancer development. These foods contain anticarcinogenic compounds such as chlorophyll, carotenoids, flavonoids, indole, polyphenols, and protease inhibitors.
Researchers have found that the foods and herbs with the highest anticarcinogenic activity are licorice, garlic, soybeans, cabbage, ginger, citrus, and the umbelliferous vegetables.
Lycopene
Lycopene is a chemical in some fruits and vegetables that has demonstrated some potential in the prevention of prostate cancer. Lycopene is being thoroughly studied in a number of ongoing trials. Lycopene is a carotenoid present in blood that has proven antioxidant activity. In vitro and in vivo studies have shown that lycopene has protective effects against some types of cancers.
Lycopene ingestion has been shown to reduce some types of digestive system cancers but has been primarily studied in association with prostate cancer. Lycopene is found primarily in nature in tomatoes and tomato products but is also found in carrots, green peppers, apricots, watermelon, and pink grapefruit. A case-control study that analyzed plasma levels of lycopene in men with prostate cancer and in healthy men found that men with the highest levels of lycopene in plasma were less likely to develop prostate cancer.8
An additional study of 12 prostate cancer patients and 12 age matched healthy subjects found significantly lower lycopene serum and tissue levels in cancer patients than in controls. A study of mortality from prostate cancer in 41 countries found that men who ingest more than 6 Kcal per day of tomatoes and tomato products have a significantly reduced risk of developing prostate cancer. A population-based case-control study of 317 prostate cancer cases and 480 controls in New Zealand found that the intake of lycopene and tomato-based foods was weakly associated with prostate cancer risk reduction. A prospective cohort study of 47,894 subjects found lycopene intake from tomato products was inversely associated with the risk of prostate cancer.
A study found that lycopene obtained by eating tomato sauce is associated with a decreased risk of prostate cancer development. A new study in mice found that lycopene has the ability to inhibit tumor formation in the prostate and that these effects are organ-specific. It is generally believed the antioxidant effects of lycopene are responsible for the tumor-inhibiting properties of lycopene, but other mechanisms may also be involved.
A more recent study found that short-term supplementation with tomato sauce containing a particular form of lycopene (all-trans-lycopene) produces signifi cant increases in total lycopene in serum and in the prostate gland. A recent review of the scientific literature found evidence that lycopene decreases the risk of developing prostate cancer. A prospective study recently found that two or more servings of tomato products or lycopene per week reduced the risk of developing prostate cancer by at least 23% compared to those who ate tomato products/lycopene less than once per month.
A study of 32 men with a history of prostate cancer and surgical prostate removal found that a diet that contains 30 milligrams of lycopene per day reduced oxidative DNA damage in prostate tissue by an average of 28 percent. This regimen also reduced PSA levels by an average of 17.5 percent. This amount of lycopene is equivalent to about threequarters of one cup of tomato sauce per day. A study from the University of California at Los Angeles found that a combination of lutein and lycopene reduced prostate cancer cell growth by 20 percent. The commonly seen autumn olive shrub produces berries that contain 18 times more lycopene than tomatoes.
A prospective study of men with a family history of prostate cancer found that the consumption of lycopene and tomato-based foods reduced the risk of developing prostate cancer. An epidemiological study found that men with a high lycopene consumption had a reduction in prostate cancer nearly half that of men with low lycopene consumption. A randomized clinical trial of men with high-grade prostate intraepithelial neoplasia found that lycopene administration can delay or prevent the progression of prostate cancer. A study of 49 men with a history of prostate cancer found that a supplement consisting of lycopene, soy, and isoflavones delayed progression of disease in most patients. New research has further demonstrated that lycopene destroys prostate cancer cells and improves the environment in which the body can rid itself of the cancer. New research has also found that other nutrients in addition to lycopene in the tomato have anti-prostate cancer effects. A new study has found that the risk of developing lycopene is inversely related to the levels of consumption of lycopene in the diet. A new study of men with metastatic prostate cancer that was unresponsive to some other therapies found that lycopene improved PSA levels and slowed the progression of disease in some patients with combined other therapies. A meta-analysis of multiple studies found that high levels of tomato and lycopene consumption significantly reduce the risk of developing prostate cancer.
Selenium
Selenium has been shown to have anticarcinogenic effects both in vitro and in clinical studies. An in vitro study of both human and mouse tumor cell lines found that selenium reduced human prostate carcinoma cell growth by 50% compared to controls. A case-control study of 164 prostate cancer patients and 152 controls with BPH found that plasma selenium levels were significantly higher in the BPH group compared to the cancer group. High levels of selenium have been found to counteract the prostate cancer cell-stimulatory effects of cadmium in vitro. A case-control study of 181 prostate cancer cases and 181 matched controls found that selenium levels in the body, as gauged by levels in the toenails, are associated with the risk of prostate cancer. In these cases, high selenium levels were associated with significantly reduced risk of advanced prostatic cancer. This held up even after controlling for a variety of factors, such as family history of prostate cancer, saturated fat intake, vasectomy, geographical region, body mass intake, and calcium intake. A study of 9345 Japanese- American men who had serum samples drawn and frozen in the 1970s and were assessed for prostate cancer incidence 20 years later found that those with selenium levels in the highest quartile were only half as likely to have disease as those in the lowest quartile. A similar study collected samples from 111 subjects in 1973 and found that the mean serum selenium levels of those with prostate cancer were significantly lower than those in 210 matched controls. A different study evaluated the effects of oral selenium supplementation on general cancer risk reduction in patients with a history of skin cancer. The researchers found no evidence that selenium supplementation affected skin cancer outcomes. However, they did find that supplementation reduced the incidence of all cancers combined, including lung, colorectal, and prostate. Selenium supplementation also reduced mortality from all cancers combined and total mortality. An additional study of 974 men with a history of basal or squamous cell carcinoma evaluated whether supplemental selenium affects the incidence of prostate cancer. The men were randomized either to 200 micrograms of selenium daily or placebo for a mean length of 4.5 years.
After an overall follow-up period of 6.5 years, the researchers found that the group receiving selenium had a significantly lower (63%) incidence of prostate cancer. The selenium group also had significantly lower total cancer incidence and overall mortality. A new study has shed some light on the mechanism by which selenium may produce some of its anti-tumor effects. This study strongly suggests selenium plays a key role in the induction of apoptosis, or programmed cell death, of prostate cells. Several ongoing trials are evaluating the ability of selenium supplementation to reduce the risk of prostate cancer. A more recent study found that men with low serum levels of selenium have some reduction in prostate cancer risk if they use selenium supplementation. A study in rats found that a diet containing broccoli sprouts and florets enriched with selenium reduced the risk of prostate cancer in treated animals.
Vitamin E
A study based on a cohort of 29,133 men found 317 developed prostate cancer during 9 years of follow-up. Baseline serum vitamin E levels were not important in prostate cancer development, but those who received high levels of vitamin E supplementation had a significantly reduced risk of developing prostate cancer. Alpha-tocopherol combined with lycopene has been shown to have strong inhibitory effects on prostate cell proliferation in vitro. A new study has discovered that long-term vitamin E supplementation is associated with decreased levels of male hormones in the blood. The lower level of hormone in the blood may be the critical factor in the found association between vitamin E supplementation and reduced risk of developing prostate cancer.
A recently completed study of 145 men who developed prostate cancer found that these men had lower plasma levels of selenium, alpha-tocopherol (a component of vitamin E), and gamma-tocopherol (another component of vitamin E) than a control group that did not have the disease. A new study discovered that vitamin E produces these antitumor effects on prostate cells by way of apoptosis (programmed cell death).
A more recent study found that a form of vitamin E called vitamin E succinate kills prostate cancer cells but leaves normal prostate cell intact. The recent Alpha Tocopherol Beta- Carotene Prevention Study found that long-term supplementation with vitamin E reduces the risk of developing prostate cancer. A recent analysis of that study found that vitamin E lowered the level of male sex hormones, a key factor in the development of prostate cancer, in the serum of the treated group. Vitamin E has been found to be an efficient regulator in the destruction of tumor cells that damage the ability of the body to fight cancerous growth. Vitamin E appears to have especially strong anti-prostate cancer effects in younger men.
Vitamin E has also shown promise in the treatment of hot fl ashes in men who have undergone hormonal treatment for prostate cancer. A study has found that vitamin E interferes with the ability of certain cells to form receptors that are crucial in the development of prostate cancer. A new study found that a combination of vitamin E and lycopene significantly reduced the progression of prostate cancer in human prostate cancer cells introduced into an animal model. The researchers also found that PSA levels are an accurate measure of disease response to the therapy. A new study of men with a history of smoking found that a combination of vitamin E, beta-carotene, and vitamin C reduced the risk of developing prostate cancer. Additional evidence has found that a combination of vitamin E, lycopene, and selenium reduces the risk of developing prostate cancer. A new randomized-controlled trial found that vitamin E supplementation reduces the risk of prostate cancer when vitamin E levels in the blood are increased.
A different study also found evidence that vitamin E supplementation led to higher alpha-tocopherol levels in the blood which is associated with a decreased of developing disease and a reduction in disease progression in those with disease. A new study has found that a combination of vitamin E and vitamin C significantly inhibits the growth of human prostate cancer cells.
Vitamin D
A study in rats found that an analog of vitamin D suppressed tumor development in the animals. A different study in rats found that the administration of hormonal analog of vitamin D, 1, 25-dihydroxyvitamin D (calcitriol) and a different vitamin D analog called EB1089 led to significantly smaller prostate tumor volumes than a control solution. An additional study also found evidence that 1,25-dihydroxyvitamin D inhibits the growth of both primary cultures of human prostate cancer cells and cancer cell lines. Yet another study found that 1 alpha, 25-dihydroxyvitamin D can inhibit the invasive growth properties of the human prostate carcinoma lines, DU 145, PC-3, and LNCaP, in vitro.
Epidemiological studies in humans have suggested vitamin D deficiency is an important factor in the development of prostate cancer. A new study has found that prostate cancer cells lack a component of vitamin D that is typically present in healthy prostate cells. The same component found in this study, 1 alpha,25(OH)(2)D(3), may be a useful prostate cancer treatment when combined with previously-used therapies. Another new study has found further evidence that this component of vitamin D can inhibit the growth of prostate cancer cells.
Recent research suggests a compound related to vitamin D called 1 alpha, 25 Dihydroxyvitamin D(3) (calcitriol) can alter certain mechanisms within cells in the prostate and produce increased cancer fighting effects. Calcitriol is the active metabolite of vitamin D in the body. Other research has found that calcitriol can maintain vitamin D levels in men being treated for prostate cancer. These men often have significant vitamin D depletion during therapy, and this reduces the effectiveness of treatment.
A recent study of 11 men being treated for prostate cancer found that combination treatment of docetaxel and calcitriol led to significant improvements in disease in all five men who completed eight weeks of therapy. Docetaxel is a commonly used chemotherapeutic drug. A different but related compound of vitamin D called analogue (V) has been found to decrease proliferation of a prostate cancer cell line called DU145. A recent review of studies involving the use of calcitriol on prostate cancer cells found significant evidence of anti-cancer effects. Researchers previously believed that calcitriol required male sex hormones to produce its anti-cancer effects, but a recent study found that this is not true. This may be an important consideration for treatment because many men with prostate cancer are treated with male hormone suppression therapy. The combination of calcitriol with a viral therapy produced powerful anti-prostate cancer cell effects in a recent study. New research suggests that maintaining normal levels of vitamin D are important in the prevention of prostate cancer. New research has uncovered the anti-prostate cancer effects of vitamin D. The researchers found that vitamin D produces its effects by inhibiting factors called prostaglandins in the body. A different study found that low levels of vitamin D are associated with an increased incidence of prostate cancer that higher levels of vitamin D in the blood as a result of diet or supplementation are associated with a decreased risk of developing the disease. An analog of vitamin D has been shown to prevent the development of prostate cancer in prostate epithelial cells. The active metabolite of vitamin D combined with ibuprofen has been shown to reduce the growth of prostate cancer cells.
Zinc
Zinc plays a major role in androgen metabolism. Estrogens appear to reduce the uptake of zinc in the intestines. Estrogen levels are increased in men with BPH and sometimes in men with prostate cancer. Zinc has been shown to decrease the size of the prostate and to decrease symptomology in BPH patients. This could have implications for prostate cancer prevention and the patient recovery after prostatectomy. Zinc has also been shown to inhibit 5-alpha-reductase activity, which reduces the conversion of testosterone to the dangerous DHT form. Zinc, like saw palmetto, has been shown to prevent the specific binding of androgens to nuclear and cytosol androgen receptors. Zinc has also been shown to inhibit prolactin secretion. As mentioned before, prolactin increases the uptake of testosterone by the prostate. This increased prolactin secretion leads to greater levels of DHT because of increased levels of substrate. Cadmium is an antagonist of zinc and is also a stimulant of 5-alpha-reductase activity. Zinc has been shown to selectively inhibit prolactin secretion from the pituitary. Prolactin secretion directly stimulates increased production of testosterone and the conversion to the more dangerous form, DHT. A new study has determined that zinc is absolutely vital to the apoptosis of prostate cancer cells through its effects on the compound known as fetuin. A different study discovered that zinc plays an important role in the regulation of tumor cell invasion of various tissues in the prostate. An additional study confirmed these tumor-inhibiting effects of zinc.
A recent study found that zinc is involved in the regulation of enzymes that are involved with the invasion and metastasis of prostate cancer cells. A study found that zinc plays a vital role in the ability of a substance called fetuin to induce apoptosis, or cell death, in a variety of cancer cell types. Fetuin itself has been found to inhibit prostate cancer development in mice. A zinc-controlled factor called Kruppel-like factor 6 (KLF6) is mutated in a significant number of prostate cancer cases. Zinc has been found in decreased levels in the cytoplasm of prostate cancer cells when compared to levels in the cytoplasm of normal prostate cells.
Essential Fatty Acids
Many BPH patients have received benefit from the administration of essential fatty acids (EFA) containing linoleic, linolenic, and arachidonic acids. For reasons stated earlier, this could have implications for prostate cancer prevention or following conventional treatment for prostate cancer such as prostatectomy. An uncontrolled study of 19 subjects found reduction in residual urine in 12 of the subjects after several weeks of treatment.
This study confirmed other research that suggests EFA deficiencies in BHP and prostate cancer patients. The combination of linoleic, linolenic, and arachidonic acids appears to be a critical factor in producing beneficial therapeutic effects. A study found that severity of disease progression in a group of 49 prostate cancer patients was associated with a lower ratio of polyunsaturated-to saturated fats in prostate tissue. The polyunsaturated fats found in the study included linolenic acid, omega-3, and omega-6. A different study found that two commercial preparations of conjugated linoleic acid had inhibitory effects on the proliferation of prostate cancer cells. A new study has found that the risk of developing prostate cancer and locally-advanced prostate carcinoma are associated with low levels of polyunsaturated fatty acid in the prostate. Newer research has found that dietary linoleic acid consumption is inversely related to the risk of developing prostate cancer.
Corn Oil
Evidence is emerging that the ingestion of large quantities of corn oil may increase the risk of developing prostate cancer and stimulating the growth of prostate cancer cells once developed. A study in mice found that corn oil and linoleic acid stimulated the growth of prostate cancer cells called DU145.44 Rats fed a diet rich in corn oil (20% of fat intake) were more likely to have fast-growing prostate cancer cells than those on a fat-free diet.
An additional study found that rats fed a diet rich in fats obtained from corn oil (20%) were significantly more likely to develop carcinoma of the prostate than those fed a low-fat diet with low levels (5%) of corn oil. An additional study in mice using human prostate cancer cells that had been placed in the animals found that a diet rich (18%) in corn oil stimulated the growth of the cancerous cells to a greater extent than in mice who were fed a diet low in corn oil (5%). A more recent study found that corn oil did not promote the development of prostate cancer in rats.
Amino Acids
A combination of amino acids that includes glutamic acid, alanine, and glycine given in the form of two 6 grain capsules three times daily for 2 weeks followed by one capsule three times daily has led to BPH symptom improvement in several studies. A controlled study of 45 men with BPH found that delayed micturition occurred in 70% of cases, urine frequency was reduced in 73% of cases, nocturia was improved in 95% of cases, and urgency was reduced in 81% of cases.
Cholesterol
Cholesterol is an important factor in the formation of sexual hormones. Evidence indicates that cholesterol-lowering drugs have a beneficial effect on androgen formation in the prostate. A diet low in saturated fat coupled with regular aerobic exercise can reduce cholesterol levels in most individuals.
Soy
As previously noted, Asian populations have a reduced prevalence of progressive prostate cancer compared to Western populations. This may be due to generally high dietary soybean ingestion in these populations. Soybeans have abundant quantities of phytoesterols. Phytoesterols are known to have cholesterol-lowering properties. Phytoesterols have demonstrated positive effects in treating BPH. A double-blind study evaluated the administration of 20 mg beta-sitosterol, a phytoesterol in soy, three times daily or placebo to 200 men with BPH. Beta-sitosterol increased maximum urinary flow rates from 9.9 ml/s to 15.2 ml/s and decreased mean residual urinary volume from 65.8 ml to 30.4 ml. The placebo group had no significant changes. Typical Western diets provide only about 80 mg/day of phytosterols compared to a traditional Japanese diet, which provides about 400 mg/day. A three-and-a-half ounce serving of soybeans or tofu contains about 90 mg of beta-sitosterol. Higher consumption levels of soy and soyfoods have also been associated with a reduced risk of prostate cancer. Two separate studies have attributed this effect to the isofl avinoids called daidzein and genistein. Both of these agents have demonstrated 5-alpha-reductase reduction activity.
Saponins are another class of compound found in soybeans. Saponins are also found in many other types of plants. They are known to have a variety of anti-cancer properties. Phytates are another compound found in soybeans and in other plants. Phytates have been shown to increase natural killer cell activity in the body. The phytoestrogens found in soy are known to have anti-estrogenic effects. Again, this can have important effects in the prevention of prostate cancer. It has been suggested that, in general, phytoestrogens have enzyme inhibition action, which could lead to inhibition of 5-alpha-reductase activity.
Asian cultures are believed to consume about 20-80 mg/day of genistein, whereas Western populations consume about 2-3 mg/day. Messina and colleagues performed a review of 26 animal studies involving genistein and found that 17 (65%) of them demonstrated evidence of anticarcinogenic activity from this compound. It is believed that genistein is a natural PTK inhibitor. PTK inhibition has been found to be major factor in the inhibition of cancer. In vitro research has suggested genistein is a strong inhibitor of angiogenesis, a major factor in the growth of cancer cells. Studies involving human volunteers who consumed soy beverages that contained 42 mg of genistein and 27 mg of daidzein daily produced peripheral blood concentrations of 0.5-1.0 ?M. This is known to be an insufficient quantity to inhibit the growth of cultured cancer cells. This suggests that these compounds may have a more important role as chemopreventative rather than chemotherapeutic agents.
Additional epidemiologic data has found that Japanese men have plasma levels of these isoflavone compounds that are 7 to 110 times higher than those in Finnish men. The major constituent of these isofl avone concentrations is genistein. Researchers have suggested genistein may have a variety of mechanisms that prevent cancer formation, including direct growth inhibition, apoptosis induction, and cancer cell adhesion. An in vitro study suggests that eqoul, biochanin A, and genistein are all potent inhibitors of 5-alphareductase.
Animal studies have suggested a diet high in genistein and daidzein resulted in a lower incidence of prostate cancer and longer disease-free periods after exposure to carcinogenic materials compared to a low isoflavone diet. The isoflavones genistein and biochanin A inhibited many different human prostate cancer cell lines, but this effect did not occur with daidzein. A new study found that 50 healthy men who received 50 mg of soy isoflavone twice daily for three weeks had an increase in antioxidant activity in prostate cells that could inhibit the formation of prostate cancer cells. A different study found that the administration of genistein to prostate cancer cells already receiving radiation therapy increased the therapeutic effect of the therapy. An additional study has found that low doses of genistein can induce apoptosis in human prostate cancer cells.
A more recent study in rats found that genistein in the diet decreased the incidence of poorly differentiated prostate tumors. Researchers have also found that genistein regulates the expression of prostate-specific antigen, a key indicator of disease, in prostate cancer cells. A different study found that genistein inhibited the proliferation of two prostate cancer cells lines (LNCaP and PC-3) by regulating an enzyme called glutathione peroxidase. A recent study in mice found that genistein reduced the risk of developing prostate carcinoma in a dose-dependent manner. An additional study found that 50 mg of genistein twice daily for three weeks led to changes in healthy male subjects that are known to reduce the risk of developing prostate cancer. A randomized study of 35 Japanese men found that 400 ml daily consumption of soymilk led to significant decreases in serum levels of estrone, a hormone that may be an important factor in the development of prostate cancer. A new study has found that a supplement containing soy, isoflavones, lycopene, and other antioxidants significantly reduced PSA levels in patients with a history of prostate cancer. A meta-analysis of eight clinical studies found that regular consumption of soy foods reduces the risk of developing prostate cancer by about 30%.
Drug and Pesticide Avoidance
A variety of pesticides have been shown to produce changes that increase the activity of 5-alpha-reductase. Some of these compounds include dioxin, polyhalogenated biphenyls, hexachlorobenzene, diethylstilbestrol (DES), and dibenzofurans. A diet that avoids exposure to these agents is recommend for the prevention and treatment of prostate cancer.
Alcohol Avoidance
Beer ingestion has been associated with increased secretion of prolactin, which increases both testosterone formation and dihydrotestosterone conversion. Alcohol intake, in general, has negative effects on the prostate as evidence by a 17-year study of 6,581 men in Hawaii. This study found that alcohol intake of at least 25 ounces per month was directly correlated with the development of BPH.
Saw Palmetto (Serenoa repens)
As mentioned earlier, there is no known connection between BPH and prostate cancer other than the fact that they have some similarities in etiology and symptoms. In both cases, the conversion of serum testosterone to DHT in the prostate gland appears to be an important part of the disease process. The drug finasteride has been used to treat BPH and is being studied in prostate cancer prevention trials. Finasteride works by inhibiting the conversion of testosterone to DHT. It accomplishes this by blocking the effects of 5-alpha-reductase, which converts testosterone to DHT.
Saw palmetto is the fat-soluble medicinal fraction obtained from the small palm tree called Serenoa repens, which grows in the West Indies and southeast Atlantic coast of North America.Saw palmetto extract has been found to inhibit the conversion of testosterone to DHT in the prostate. It has also demonstrated anti-estrogenic and receptor site-binding effects. Surprisingly, estrogen has been found to contribute to the effects of BPH and possibly prostate cancer because it reduces the ability of the prostate to clear DHT levels.
A double-blind study of 35 men with BPH found that men given 160 mg of saw palmetto extract daily for 90 days had lower receptor values for estrogen and progesterone than those in a placebo group. The researchers also found that saw palmetto extract blocks the translocation of the cytosol androgen receptor to the nucleus. The overall implications of the study are that saw palmetto extract has both anti-estrogenic and anti-androgenic effects. A double-blind, placebo controlled study involving 110 BPH patients over 28 days found that saw palmetto administration significantly improved BPH symptoms, such as dysuria, nocturia, prostate volume, and residual urine.
Finasteride has had similar positive effects in the control of BPH but can take up to a year for the effects to occur, whereas saw palmetto generally produces positive effects in as little as 30 days and without serious adverse effects. Saw palmetto does not appear to effect PSA levels. New research has discovered that men treated with saw palmetto had greater improvement in urinary tract symptoms associated with BPH than those who received placebo. A new randomized study of 44 men aged 45-80 years found that men receiving saw palmetto had improvement in symptoms associated with BPH, though this improvement did not reach statistical significance.
A new microbiological study found that the application of an extract of saw palmetto to prostate cells led to increased rates of cell apoptosis. Researchers have found that saw palmetto has effects at the most basic physiologic levels by interfering with the effects of a hormone called prolactin and its stimulation of prostate cell proliferation. A different group of researchers isolated a component of saw palmetto called myristoleic acid that induces cell death in the LNCaP line of prostate cancer cells. Another study found that an extract of saw palmetto inhibits the activity of an enzyme that is important in the development of prostate cancer. An extract of saw palmetto has been found to inhibit the activity of another enzyme called cyclooxygenase-2, which has been implicated in the progression of prostate cancer. A recent study found that an extract of saw palmetto had equivalent therapeutic effects and fewer side effects as a commonly prescribed medication for prostate enlargement, a risk factor for development of prostate cancer.
Researchers found that saw palmetto has specific effects on mast cell accumulation and epithelium atrophy that may be responsible for its positive effects on prostatic hypertrophy and prostate cancer development. A saw palmetto extract has been found to be inhibitor of the enzyme 5alpha-reductase, which is the key factor in the development of prostate cancer. A different study also found that saw palmetto inhibits 5alpha-reducase in human prostate cancer cell lines without affecting PSA levels.
Bitter Almond (Pygeum Africanum)
Pygeum africanum is an evergreen tree native to Africa. The fatty acids of the extract have similar properties to those of saw palmetto. The tree also contains esters of ferulic acid, which have effects on the endocrine system. Studies have shown that docosanol reduces levels of testosterone and leutinizing hormone. Docosanol is a compound that has been found in Pygeum africanum. Docosanol has been found to reduce prolactin levels in the body. Prolactin increases the uptake of testosterone and increases the conversion of testosterone to DHT in the body. Pygeum contains quantities of docosanol but the esters of ferulic acid have similar activity and are found in greater concentrations and are more bioavailable in pygeum than docosanol. Ferulic acid esters have been shown to reduce the cholesterol content in the prostate. Cholesterol end-products in the prostate have been associated with both BPH and cancer.
The sterolic portion of pygeum also works against the accumulation of testosterone in the prostate. Double-blind studies have found that standardized pygeum extract, like that of saw palmetto, improved a variety of urinary symptoms associated with BPH, such as urinary frequency, nocturia, flow interruption, after-dribbling, weak stream, and hesitation. Pygeum has also been found to increase prostatic secretions and improve the composition of the seminal fluid. Standardized pygeum extract has also been found in double blind clinical trials to improve the capacity of BPH patients to achieve erections. All of these factors suggest a role for pygeum in prostate cancer patients who have received a prostatectomy, and possibly a role in the prevention of disease. A double-blind study found that saw palmetto was more effective than pygeum extract in most measures of BPH, but pygeum has better proven effects on prostate secretion. The standardized extract of pygeum is 14% triterpenes including betasitosterol and 0.5% n-docosanol. The typical dose is 100-200 mg per day in divided doses. The crude herb is not used therapeutically.
New research in rat prostate tissues suggests pygeum africanum extract has positive effects on processes associated with BPH development. An additional study in animal tissues found further evidence of positive effects from pygeum africanum administration on infl ammatory effects associated with the development of BPH. A review of 18 controlled clinical trials involving 1,562 men found that men treated with pygeum africanum for at least 30 days were more than twice as likely as controls to have symptom improvement associated with BPH than those receiving placebo. Researchers have recently isolated an extract of pygeum africanum called V-1326 that may be responsible for its positive effects on prostate enlargement and the inhibition of prostate cancer development. A review of 18 randomized controlled trials found that Pygeum africanum is an effective treatment for an enlarged prostate and may have preventative effects on prostate cancer development. A study in rats found that an extract of Pygeum africanum called Tadenan counteracted many of the harmful physiologic effects of dihydrotestosterone. A different study involving rats found that Tadenan has a variety of physiologic effects that inhibit the proliferation of prostate cells.
Cernilton
Clinicians in Europe have used an extract of flower pollen called Cernilton for more than 35 years to treat prostatitis and BPH. Double-blind clinical trials have shown that Cernilton improved BPH patients at an overall success rate of 70%. Nocturia and diurnal frequency symptoms improve in about 70% of patients. Researchers have found evidence that Cernilton contains a substance that can inhibit the growth of prostate cells. A study of 79 males aged 62-89 evaluated the effects of the administration of 63 mg Cernilton pollen extract daily for 12 weeks. The mean baseline prostatic volume was 33.2 cm.
During the study period, maximum urinary flow rate increased from 5.1 to 6.0 ml/sec. Average flow rates increased from 9.3 to 11 ml/sec. In addition, residual urinary flow rates decreased from 54.2 ml to below 30 ml. Furthermore, all of the following measures improved in these patients: urgency, intermittency, delayed voiding, post-void dribbling, prolonged voiding, incomplete emptying, dysuria, and nocturia. Cernilton demonstrated 50% inhibition on DU145 cell line growth after 2 days exposure at 5 mcg/ml. A recent review of studies involving cernilton for the treatment of BPH found that cernilton modestly improves urologic symptoms associated with BPH.
A review of studies involving cernilton and its effects on prostate enlargement found that cernilton improved urinary symptoms compared to a group receiving Tadenan and a control group in men with this condition. A study of an extract of cernilton called DIBOA found that this compound inhibited the growth of DU-145 prostate cancer cells. An additional study confirmed the inhibitory effects of DIBOA on a prostate cancer cell line. A randomized study of 243 patients with urinary disturbances associated with benign prostatic hyperplasia found that a combination of tamsulosin hydrochloride with cernilton led to significant improvement in urinary symptoms. Urinary difficulties are also a significant problem in prostate cancer patients. A study has also found that cernilton pollen extract protects the epithelial cells lining the prostate, inhibits the proliferation of prostate cells, and enhances apoptosis of abnormal cells.
Urtica dioica (stinging needles)
Urtica dioica has also been found to have beneficial effects in the treatment of BPH. Two double-blind studies have shown it to have greater efficacy in treating BPH than placebo. The range of efficacy in this plant appears to be comparable to that of pygeum. This ranks it lower than saw palmetto for the treatment of BPH and in prostate cancer prevention potential. The effects of Urtica dioica are similar to those of saw palmetto in that its main activity appears to be the interference of dihydrotestosterone binding to both cystolic and nuclear receptors. This suggests a role in the prevention of prostate cancer. A study of 431 patients with BPH found that a combination therapy composed of extracts from saw palmetto and urticadioica was as effective as finasteride in treating the symptoms of disease. A recent study found that a 20% extract of Urtica dioica had significant antiproliferative effects on human prostatic epithelial and stromal cells. Newer research has found the mechanisms produced by Urtica dioica that produce the anti prostate cancer effects. The researchers identified adenosine deaminase inhibition as the key effect in the prevention of prostate cancer cell growth.
Garlic
A compound in aged garlic significantly inhibited the growth of human prostate cancer cells in vitro. A new study has demonstrated that garlic has properties that can detoxify cancer-producing factors. Preliminary studies with allium, a component of garlic, suggest this compound has strong anti-tumor properties in both prostate and breast cancer cells. A different study found evidence that a constituent of garlic called S-allylmercaptocyste has anti-tumor effects in prostate cells by converting the breakdown products of testosterone into less harmful substances.
A review article has cited new evidence for the antiproliferative effects of garlic on prostate cancer. An additional study found further evidence of the ability of garlic-derived allium to inhibit the proliferation of the LNCaP prostate cancer cell line. A case-control study of 328 men diagnosed with prostate cancer found that men who consumed two or more servings of garlic per week had a 44% decreased risk of developing prostate cancer compared to those who never ate garlic. A newer study has found that a compound in garlic called diallyl disulfide inhibits the growth of prostate cancer cells. An additional study found similar results and identified diallyl disulfide as the key factor in the apoptosis (cell death) of prostate cancer cells.
Citrus Pectin
Citrus pectin is a soluble component of plant fiber that is derived from citrus fruit. There is some evidence that citrus pectin can inhibit prostate cell formation and growth. A study in rats found that animals given 1.0% by volume citrus pectin in their drinking water had statistically significant reductions in the metastasis of prostate carcinoma compared to control animals. A study involving mice found that the administration of high-dose(1.6 mg/ml) modifi ed citrus pectin inhibited the tumor size after 20 days compared to controls. A study of cancerous human prostate cells found that the addition of modified citrus pectin to the culture interfered with the mechanisms necessary for the cancer cells to multiply. There is a significant amount of interest in studying modified citrus pectin for its anti-metastatic effects. A newer study found evidence for the first time that modified citrus pectin may reduce the growth of solid primary tumors.
Green Tea
Green tea has been shown to have inhibitory effects on prostate cancer cell growth. Studies in rats suggest that compounds contained in green tea inhibit the activity of 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone, which has carcinogenic effects in the prostate. Researchers have found that the most potent of these compounds is called epigallocatechin-3-gallate (EGCG). A study in rats found that green tea has inhibitory effects on other enzymes associated with the growth of prostate cancer cells. EGCG has been found in high concentrations in the serum of green tea drinkers. EGCG and other compounds in green tea inhibit the activity of the enzyme called proteasome, a key factor in the formation of prostate cancer.
A recent review cited evidence that green tea can inhibit the formation of prostate cancer. A study in rats found that polyphenone-60, an extract of green tea, interfered with an enzyme called aromatase, which is known to be a key factor in the development of prostate cancer. Epidemiological evidence suggests green tea reduces the risk of developing prostate cancer, and a new study suggests green tea provides these protective effects by depleting levels of polyamines, which are an important part of cellular proliferation. A different study found evidence that green tea catechins inhibit some of the conversion of testosterone to dihydrotestosterone. A recent study in mice found that a polyphenolic fraction isolated from green tea not only inhibited localized prostate cancer growth but also inhibited the metastasis of the cancer to distant sites. A different study found that several catechins from green tea suppressed the growth of prostate cancer DU-145 cells.
Spices
Spices add flavor to food but also may have cancer-fighting properties. India has one of the lowest cancer rates in the world, and the people there typically eat a diet containing a wide variety of spices. There is some limited evidence that capsaicin, the component of chile peppers that makes them hot, has some anti-cancerous properties. Both curry and cumin contain turmeric, which has been found to have anti-carcinogenic properties in cell cultures. Research from animal studies in Asia has suggested capsaicin has antitumor effects. A study at Yale University found that capsaicin interferes with the tumor-formation process in mice.
Curcumin
In studies involving mice, curcumin has demonstrated anti-carcinogenic activity in a variety of cancers. While the mechanisms of its action are still unknown, curcumin has also demonstrated anti-carcinogenic effects in human cancer cell lines. A recent study in mice found that curcumin decreased the proliferation of both androgen-dependent and androgen-independent prostate cancer cells. A different study found that curcumin inhibits the growth of prostate cancer cells by inhibiting the enzymatic activity of tyrosine kinase at the epidermal growth factor receptor. A study determined that curcumin has great potential in the treatment of androgen-independent prostate cancer. A recent study found that curcumin inhibited both androgen-dependent and androgen independent prostate cancer cell lines, and accomplishes this by inhibiting the effects of factors called NF-kappaB and AP-1.
Other Agents
A commercial eight-herb formulation called PC-SPES fed to rats in 0.05% and 0.025% levels in the diet led to dose-dependent effects on both tumor incidence and tumor growth rate. PCSPES decreased serum testosterone in six men with prostate cancer. An additional eight of eight patients had reduced PSA levels after using PC-SPES. PCSPES has strong estrogenic activity that could cause adverse effects. A study among 16 men with hormone-refractory prostate cancer led to significant improvement in quality-of-life measures, reduction in patient pain ratings, and decreased PSA levels. Biofeedback therapies can help men with prostate cancer and prostatectomy restore pelvic muscle function. A treatment group regained continence after 51 days compared to 56 days in the control group. Acupuncture was used on 7 men who developed hot flushes after receiving castration therapy for prostate cancer. Six of the men completed 10 weeks of acupuncture therapy and had an average symptom decrease of 70%. A new study of ginseng found that a constituent called ginsenoside Rg3 demonstrated inhibitory action against a human prostate carcinoma cell line.
Evidence suggests licorice root (Glycrrhiza glabra) can decrease circulating levels of testosterone in men. A study has found that licorice root has many similar properties to that of paclitaxel, a commonly used chemotherapeutic drug. This study also provided evidence that licorice root can induce apoptosis in prostate cancer cells.
Source:Prostate Cancer Fund,(a special program of Project Cure Foundation) P.O. Box 96673, Washington, D.C. 20090-6673 • 1-800-716-2152. Photo courtesy of www.meb.uni-bonn.de
Phytonutrients
Even though there is evidence that supplementation of various nutrients to the diet can provide benefits in the prevention and therapy of prostate cancer, more benefit may be derived from obtaining various nutrients from natural sources in the diet. In fact, the National Cancer Institute recommends the ingestion of at least five servings daily of fruits and vegetables to fight the development and progression of prostate cancer.
In addition, scientists have discovered that not all nutrients have been identified in some foods. The phytochemicals known as silymarin, genistein, and epigallocatechin 3-gallate have been shown to inhibit prostate cancer cells from multiplying. Several studies have found that vegetables, fruits, and whole grains contain numerous phytonutrients that modulate cancer development. These foods contain anticarcinogenic compounds such as chlorophyll, carotenoids, flavonoids, indole, polyphenols, and protease inhibitors.
Researchers have found that the foods and herbs with the highest anticarcinogenic activity are licorice, garlic, soybeans, cabbage, ginger, citrus, and the umbelliferous vegetables.
Lycopene
Lycopene is a chemical in some fruits and vegetables that has demonstrated some potential in the prevention of prostate cancer. Lycopene is being thoroughly studied in a number of ongoing trials. Lycopene is a carotenoid present in blood that has proven antioxidant activity. In vitro and in vivo studies have shown that lycopene has protective effects against some types of cancers.
Lycopene ingestion has been shown to reduce some types of digestive system cancers but has been primarily studied in association with prostate cancer. Lycopene is found primarily in nature in tomatoes and tomato products but is also found in carrots, green peppers, apricots, watermelon, and pink grapefruit. A case-control study that analyzed plasma levels of lycopene in men with prostate cancer and in healthy men found that men with the highest levels of lycopene in plasma were less likely to develop prostate cancer.8
An additional study of 12 prostate cancer patients and 12 age matched healthy subjects found significantly lower lycopene serum and tissue levels in cancer patients than in controls. A study of mortality from prostate cancer in 41 countries found that men who ingest more than 6 Kcal per day of tomatoes and tomato products have a significantly reduced risk of developing prostate cancer. A population-based case-control study of 317 prostate cancer cases and 480 controls in New Zealand found that the intake of lycopene and tomato-based foods was weakly associated with prostate cancer risk reduction. A prospective cohort study of 47,894 subjects found lycopene intake from tomato products was inversely associated with the risk of prostate cancer.
A study found that lycopene obtained by eating tomato sauce is associated with a decreased risk of prostate cancer development. A new study in mice found that lycopene has the ability to inhibit tumor formation in the prostate and that these effects are organ-specific. It is generally believed the antioxidant effects of lycopene are responsible for the tumor-inhibiting properties of lycopene, but other mechanisms may also be involved.
A more recent study found that short-term supplementation with tomato sauce containing a particular form of lycopene (all-trans-lycopene) produces signifi cant increases in total lycopene in serum and in the prostate gland. A recent review of the scientific literature found evidence that lycopene decreases the risk of developing prostate cancer. A prospective study recently found that two or more servings of tomato products or lycopene per week reduced the risk of developing prostate cancer by at least 23% compared to those who ate tomato products/lycopene less than once per month.
A study of 32 men with a history of prostate cancer and surgical prostate removal found that a diet that contains 30 milligrams of lycopene per day reduced oxidative DNA damage in prostate tissue by an average of 28 percent. This regimen also reduced PSA levels by an average of 17.5 percent. This amount of lycopene is equivalent to about threequarters of one cup of tomato sauce per day. A study from the University of California at Los Angeles found that a combination of lutein and lycopene reduced prostate cancer cell growth by 20 percent. The commonly seen autumn olive shrub produces berries that contain 18 times more lycopene than tomatoes.
A prospective study of men with a family history of prostate cancer found that the consumption of lycopene and tomato-based foods reduced the risk of developing prostate cancer. An epidemiological study found that men with a high lycopene consumption had a reduction in prostate cancer nearly half that of men with low lycopene consumption. A randomized clinical trial of men with high-grade prostate intraepithelial neoplasia found that lycopene administration can delay or prevent the progression of prostate cancer. A study of 49 men with a history of prostate cancer found that a supplement consisting of lycopene, soy, and isoflavones delayed progression of disease in most patients. New research has further demonstrated that lycopene destroys prostate cancer cells and improves the environment in which the body can rid itself of the cancer. New research has also found that other nutrients in addition to lycopene in the tomato have anti-prostate cancer effects. A new study has found that the risk of developing lycopene is inversely related to the levels of consumption of lycopene in the diet. A new study of men with metastatic prostate cancer that was unresponsive to some other therapies found that lycopene improved PSA levels and slowed the progression of disease in some patients with combined other therapies. A meta-analysis of multiple studies found that high levels of tomato and lycopene consumption significantly reduce the risk of developing prostate cancer.
Selenium
Selenium has been shown to have anticarcinogenic effects both in vitro and in clinical studies. An in vitro study of both human and mouse tumor cell lines found that selenium reduced human prostate carcinoma cell growth by 50% compared to controls. A case-control study of 164 prostate cancer patients and 152 controls with BPH found that plasma selenium levels were significantly higher in the BPH group compared to the cancer group. High levels of selenium have been found to counteract the prostate cancer cell-stimulatory effects of cadmium in vitro. A case-control study of 181 prostate cancer cases and 181 matched controls found that selenium levels in the body, as gauged by levels in the toenails, are associated with the risk of prostate cancer. In these cases, high selenium levels were associated with significantly reduced risk of advanced prostatic cancer. This held up even after controlling for a variety of factors, such as family history of prostate cancer, saturated fat intake, vasectomy, geographical region, body mass intake, and calcium intake. A study of 9345 Japanese- American men who had serum samples drawn and frozen in the 1970s and were assessed for prostate cancer incidence 20 years later found that those with selenium levels in the highest quartile were only half as likely to have disease as those in the lowest quartile. A similar study collected samples from 111 subjects in 1973 and found that the mean serum selenium levels of those with prostate cancer were significantly lower than those in 210 matched controls. A different study evaluated the effects of oral selenium supplementation on general cancer risk reduction in patients with a history of skin cancer. The researchers found no evidence that selenium supplementation affected skin cancer outcomes. However, they did find that supplementation reduced the incidence of all cancers combined, including lung, colorectal, and prostate. Selenium supplementation also reduced mortality from all cancers combined and total mortality. An additional study of 974 men with a history of basal or squamous cell carcinoma evaluated whether supplemental selenium affects the incidence of prostate cancer. The men were randomized either to 200 micrograms of selenium daily or placebo for a mean length of 4.5 years.
After an overall follow-up period of 6.5 years, the researchers found that the group receiving selenium had a significantly lower (63%) incidence of prostate cancer. The selenium group also had significantly lower total cancer incidence and overall mortality. A new study has shed some light on the mechanism by which selenium may produce some of its anti-tumor effects. This study strongly suggests selenium plays a key role in the induction of apoptosis, or programmed cell death, of prostate cells. Several ongoing trials are evaluating the ability of selenium supplementation to reduce the risk of prostate cancer. A more recent study found that men with low serum levels of selenium have some reduction in prostate cancer risk if they use selenium supplementation. A study in rats found that a diet containing broccoli sprouts and florets enriched with selenium reduced the risk of prostate cancer in treated animals.
Vitamin E
A study based on a cohort of 29,133 men found 317 developed prostate cancer during 9 years of follow-up. Baseline serum vitamin E levels were not important in prostate cancer development, but those who received high levels of vitamin E supplementation had a significantly reduced risk of developing prostate cancer. Alpha-tocopherol combined with lycopene has been shown to have strong inhibitory effects on prostate cell proliferation in vitro. A new study has discovered that long-term vitamin E supplementation is associated with decreased levels of male hormones in the blood. The lower level of hormone in the blood may be the critical factor in the found association between vitamin E supplementation and reduced risk of developing prostate cancer.
A recently completed study of 145 men who developed prostate cancer found that these men had lower plasma levels of selenium, alpha-tocopherol (a component of vitamin E), and gamma-tocopherol (another component of vitamin E) than a control group that did not have the disease. A new study discovered that vitamin E produces these antitumor effects on prostate cells by way of apoptosis (programmed cell death).
A more recent study found that a form of vitamin E called vitamin E succinate kills prostate cancer cells but leaves normal prostate cell intact. The recent Alpha Tocopherol Beta- Carotene Prevention Study found that long-term supplementation with vitamin E reduces the risk of developing prostate cancer. A recent analysis of that study found that vitamin E lowered the level of male sex hormones, a key factor in the development of prostate cancer, in the serum of the treated group. Vitamin E has been found to be an efficient regulator in the destruction of tumor cells that damage the ability of the body to fight cancerous growth. Vitamin E appears to have especially strong anti-prostate cancer effects in younger men.
Vitamin E has also shown promise in the treatment of hot fl ashes in men who have undergone hormonal treatment for prostate cancer. A study has found that vitamin E interferes with the ability of certain cells to form receptors that are crucial in the development of prostate cancer. A new study found that a combination of vitamin E and lycopene significantly reduced the progression of prostate cancer in human prostate cancer cells introduced into an animal model. The researchers also found that PSA levels are an accurate measure of disease response to the therapy. A new study of men with a history of smoking found that a combination of vitamin E, beta-carotene, and vitamin C reduced the risk of developing prostate cancer. Additional evidence has found that a combination of vitamin E, lycopene, and selenium reduces the risk of developing prostate cancer. A new randomized-controlled trial found that vitamin E supplementation reduces the risk of prostate cancer when vitamin E levels in the blood are increased.
A different study also found evidence that vitamin E supplementation led to higher alpha-tocopherol levels in the blood which is associated with a decreased of developing disease and a reduction in disease progression in those with disease. A new study has found that a combination of vitamin E and vitamin C significantly inhibits the growth of human prostate cancer cells.
Vitamin D
A study in rats found that an analog of vitamin D suppressed tumor development in the animals. A different study in rats found that the administration of hormonal analog of vitamin D, 1, 25-dihydroxyvitamin D (calcitriol) and a different vitamin D analog called EB1089 led to significantly smaller prostate tumor volumes than a control solution. An additional study also found evidence that 1,25-dihydroxyvitamin D inhibits the growth of both primary cultures of human prostate cancer cells and cancer cell lines. Yet another study found that 1 alpha, 25-dihydroxyvitamin D can inhibit the invasive growth properties of the human prostate carcinoma lines, DU 145, PC-3, and LNCaP, in vitro.
Epidemiological studies in humans have suggested vitamin D deficiency is an important factor in the development of prostate cancer. A new study has found that prostate cancer cells lack a component of vitamin D that is typically present in healthy prostate cells. The same component found in this study, 1 alpha,25(OH)(2)D(3), may be a useful prostate cancer treatment when combined with previously-used therapies. Another new study has found further evidence that this component of vitamin D can inhibit the growth of prostate cancer cells.
Recent research suggests a compound related to vitamin D called 1 alpha, 25 Dihydroxyvitamin D(3) (calcitriol) can alter certain mechanisms within cells in the prostate and produce increased cancer fighting effects. Calcitriol is the active metabolite of vitamin D in the body. Other research has found that calcitriol can maintain vitamin D levels in men being treated for prostate cancer. These men often have significant vitamin D depletion during therapy, and this reduces the effectiveness of treatment.
A recent study of 11 men being treated for prostate cancer found that combination treatment of docetaxel and calcitriol led to significant improvements in disease in all five men who completed eight weeks of therapy. Docetaxel is a commonly used chemotherapeutic drug. A different but related compound of vitamin D called analogue (V) has been found to decrease proliferation of a prostate cancer cell line called DU145. A recent review of studies involving the use of calcitriol on prostate cancer cells found significant evidence of anti-cancer effects. Researchers previously believed that calcitriol required male sex hormones to produce its anti-cancer effects, but a recent study found that this is not true. This may be an important consideration for treatment because many men with prostate cancer are treated with male hormone suppression therapy. The combination of calcitriol with a viral therapy produced powerful anti-prostate cancer cell effects in a recent study. New research suggests that maintaining normal levels of vitamin D are important in the prevention of prostate cancer. New research has uncovered the anti-prostate cancer effects of vitamin D. The researchers found that vitamin D produces its effects by inhibiting factors called prostaglandins in the body. A different study found that low levels of vitamin D are associated with an increased incidence of prostate cancer that higher levels of vitamin D in the blood as a result of diet or supplementation are associated with a decreased risk of developing the disease. An analog of vitamin D has been shown to prevent the development of prostate cancer in prostate epithelial cells. The active metabolite of vitamin D combined with ibuprofen has been shown to reduce the growth of prostate cancer cells.
Zinc
Zinc plays a major role in androgen metabolism. Estrogens appear to reduce the uptake of zinc in the intestines. Estrogen levels are increased in men with BPH and sometimes in men with prostate cancer. Zinc has been shown to decrease the size of the prostate and to decrease symptomology in BPH patients. This could have implications for prostate cancer prevention and the patient recovery after prostatectomy. Zinc has also been shown to inhibit 5-alpha-reductase activity, which reduces the conversion of testosterone to the dangerous DHT form. Zinc, like saw palmetto, has been shown to prevent the specific binding of androgens to nuclear and cytosol androgen receptors. Zinc has also been shown to inhibit prolactin secretion. As mentioned before, prolactin increases the uptake of testosterone by the prostate. This increased prolactin secretion leads to greater levels of DHT because of increased levels of substrate. Cadmium is an antagonist of zinc and is also a stimulant of 5-alpha-reductase activity. Zinc has been shown to selectively inhibit prolactin secretion from the pituitary. Prolactin secretion directly stimulates increased production of testosterone and the conversion to the more dangerous form, DHT. A new study has determined that zinc is absolutely vital to the apoptosis of prostate cancer cells through its effects on the compound known as fetuin. A different study discovered that zinc plays an important role in the regulation of tumor cell invasion of various tissues in the prostate. An additional study confirmed these tumor-inhibiting effects of zinc.
A recent study found that zinc is involved in the regulation of enzymes that are involved with the invasion and metastasis of prostate cancer cells. A study found that zinc plays a vital role in the ability of a substance called fetuin to induce apoptosis, or cell death, in a variety of cancer cell types. Fetuin itself has been found to inhibit prostate cancer development in mice. A zinc-controlled factor called Kruppel-like factor 6 (KLF6) is mutated in a significant number of prostate cancer cases. Zinc has been found in decreased levels in the cytoplasm of prostate cancer cells when compared to levels in the cytoplasm of normal prostate cells.
Essential Fatty Acids
Many BPH patients have received benefit from the administration of essential fatty acids (EFA) containing linoleic, linolenic, and arachidonic acids. For reasons stated earlier, this could have implications for prostate cancer prevention or following conventional treatment for prostate cancer such as prostatectomy. An uncontrolled study of 19 subjects found reduction in residual urine in 12 of the subjects after several weeks of treatment.
This study confirmed other research that suggests EFA deficiencies in BHP and prostate cancer patients. The combination of linoleic, linolenic, and arachidonic acids appears to be a critical factor in producing beneficial therapeutic effects. A study found that severity of disease progression in a group of 49 prostate cancer patients was associated with a lower ratio of polyunsaturated-to saturated fats in prostate tissue. The polyunsaturated fats found in the study included linolenic acid, omega-3, and omega-6. A different study found that two commercial preparations of conjugated linoleic acid had inhibitory effects on the proliferation of prostate cancer cells. A new study has found that the risk of developing prostate cancer and locally-advanced prostate carcinoma are associated with low levels of polyunsaturated fatty acid in the prostate. Newer research has found that dietary linoleic acid consumption is inversely related to the risk of developing prostate cancer.
Corn Oil
Evidence is emerging that the ingestion of large quantities of corn oil may increase the risk of developing prostate cancer and stimulating the growth of prostate cancer cells once developed. A study in mice found that corn oil and linoleic acid stimulated the growth of prostate cancer cells called DU145.44 Rats fed a diet rich in corn oil (20% of fat intake) were more likely to have fast-growing prostate cancer cells than those on a fat-free diet.
An additional study found that rats fed a diet rich in fats obtained from corn oil (20%) were significantly more likely to develop carcinoma of the prostate than those fed a low-fat diet with low levels (5%) of corn oil. An additional study in mice using human prostate cancer cells that had been placed in the animals found that a diet rich (18%) in corn oil stimulated the growth of the cancerous cells to a greater extent than in mice who were fed a diet low in corn oil (5%). A more recent study found that corn oil did not promote the development of prostate cancer in rats.
Amino Acids
A combination of amino acids that includes glutamic acid, alanine, and glycine given in the form of two 6 grain capsules three times daily for 2 weeks followed by one capsule three times daily has led to BPH symptom improvement in several studies. A controlled study of 45 men with BPH found that delayed micturition occurred in 70% of cases, urine frequency was reduced in 73% of cases, nocturia was improved in 95% of cases, and urgency was reduced in 81% of cases.
Cholesterol
Cholesterol is an important factor in the formation of sexual hormones. Evidence indicates that cholesterol-lowering drugs have a beneficial effect on androgen formation in the prostate. A diet low in saturated fat coupled with regular aerobic exercise can reduce cholesterol levels in most individuals.
Soy
As previously noted, Asian populations have a reduced prevalence of progressive prostate cancer compared to Western populations. This may be due to generally high dietary soybean ingestion in these populations. Soybeans have abundant quantities of phytoesterols. Phytoesterols are known to have cholesterol-lowering properties. Phytoesterols have demonstrated positive effects in treating BPH. A double-blind study evaluated the administration of 20 mg beta-sitosterol, a phytoesterol in soy, three times daily or placebo to 200 men with BPH. Beta-sitosterol increased maximum urinary flow rates from 9.9 ml/s to 15.2 ml/s and decreased mean residual urinary volume from 65.8 ml to 30.4 ml. The placebo group had no significant changes. Typical Western diets provide only about 80 mg/day of phytosterols compared to a traditional Japanese diet, which provides about 400 mg/day. A three-and-a-half ounce serving of soybeans or tofu contains about 90 mg of beta-sitosterol. Higher consumption levels of soy and soyfoods have also been associated with a reduced risk of prostate cancer. Two separate studies have attributed this effect to the isofl avinoids called daidzein and genistein. Both of these agents have demonstrated 5-alpha-reductase reduction activity.
Saponins are another class of compound found in soybeans. Saponins are also found in many other types of plants. They are known to have a variety of anti-cancer properties. Phytates are another compound found in soybeans and in other plants. Phytates have been shown to increase natural killer cell activity in the body. The phytoestrogens found in soy are known to have anti-estrogenic effects. Again, this can have important effects in the prevention of prostate cancer. It has been suggested that, in general, phytoestrogens have enzyme inhibition action, which could lead to inhibition of 5-alpha-reductase activity.
Asian cultures are believed to consume about 20-80 mg/day of genistein, whereas Western populations consume about 2-3 mg/day. Messina and colleagues performed a review of 26 animal studies involving genistein and found that 17 (65%) of them demonstrated evidence of anticarcinogenic activity from this compound. It is believed that genistein is a natural PTK inhibitor. PTK inhibition has been found to be major factor in the inhibition of cancer. In vitro research has suggested genistein is a strong inhibitor of angiogenesis, a major factor in the growth of cancer cells. Studies involving human volunteers who consumed soy beverages that contained 42 mg of genistein and 27 mg of daidzein daily produced peripheral blood concentrations of 0.5-1.0 ?M. This is known to be an insufficient quantity to inhibit the growth of cultured cancer cells. This suggests that these compounds may have a more important role as chemopreventative rather than chemotherapeutic agents.
Additional epidemiologic data has found that Japanese men have plasma levels of these isoflavone compounds that are 7 to 110 times higher than those in Finnish men. The major constituent of these isofl avone concentrations is genistein. Researchers have suggested genistein may have a variety of mechanisms that prevent cancer formation, including direct growth inhibition, apoptosis induction, and cancer cell adhesion. An in vitro study suggests that eqoul, biochanin A, and genistein are all potent inhibitors of 5-alphareductase.
Animal studies have suggested a diet high in genistein and daidzein resulted in a lower incidence of prostate cancer and longer disease-free periods after exposure to carcinogenic materials compared to a low isoflavone diet. The isoflavones genistein and biochanin A inhibited many different human prostate cancer cell lines, but this effect did not occur with daidzein. A new study found that 50 healthy men who received 50 mg of soy isoflavone twice daily for three weeks had an increase in antioxidant activity in prostate cells that could inhibit the formation of prostate cancer cells. A different study found that the administration of genistein to prostate cancer cells already receiving radiation therapy increased the therapeutic effect of the therapy. An additional study has found that low doses of genistein can induce apoptosis in human prostate cancer cells.
A more recent study in rats found that genistein in the diet decreased the incidence of poorly differentiated prostate tumors. Researchers have also found that genistein regulates the expression of prostate-specific antigen, a key indicator of disease, in prostate cancer cells. A different study found that genistein inhibited the proliferation of two prostate cancer cells lines (LNCaP and PC-3) by regulating an enzyme called glutathione peroxidase. A recent study in mice found that genistein reduced the risk of developing prostate carcinoma in a dose-dependent manner. An additional study found that 50 mg of genistein twice daily for three weeks led to changes in healthy male subjects that are known to reduce the risk of developing prostate cancer. A randomized study of 35 Japanese men found that 400 ml daily consumption of soymilk led to significant decreases in serum levels of estrone, a hormone that may be an important factor in the development of prostate cancer. A new study has found that a supplement containing soy, isoflavones, lycopene, and other antioxidants significantly reduced PSA levels in patients with a history of prostate cancer. A meta-analysis of eight clinical studies found that regular consumption of soy foods reduces the risk of developing prostate cancer by about 30%.
Drug and Pesticide Avoidance
A variety of pesticides have been shown to produce changes that increase the activity of 5-alpha-reductase. Some of these compounds include dioxin, polyhalogenated biphenyls, hexachlorobenzene, diethylstilbestrol (DES), and dibenzofurans. A diet that avoids exposure to these agents is recommend for the prevention and treatment of prostate cancer.
Alcohol Avoidance
Beer ingestion has been associated with increased secretion of prolactin, which increases both testosterone formation and dihydrotestosterone conversion. Alcohol intake, in general, has negative effects on the prostate as evidence by a 17-year study of 6,581 men in Hawaii. This study found that alcohol intake of at least 25 ounces per month was directly correlated with the development of BPH.
Saw Palmetto (Serenoa repens)
As mentioned earlier, there is no known connection between BPH and prostate cancer other than the fact that they have some similarities in etiology and symptoms. In both cases, the conversion of serum testosterone to DHT in the prostate gland appears to be an important part of the disease process. The drug finasteride has been used to treat BPH and is being studied in prostate cancer prevention trials. Finasteride works by inhibiting the conversion of testosterone to DHT. It accomplishes this by blocking the effects of 5-alpha-reductase, which converts testosterone to DHT.
Saw palmetto is the fat-soluble medicinal fraction obtained from the small palm tree called Serenoa repens, which grows in the West Indies and southeast Atlantic coast of North America.Saw palmetto extract has been found to inhibit the conversion of testosterone to DHT in the prostate. It has also demonstrated anti-estrogenic and receptor site-binding effects. Surprisingly, estrogen has been found to contribute to the effects of BPH and possibly prostate cancer because it reduces the ability of the prostate to clear DHT levels.
A double-blind study of 35 men with BPH found that men given 160 mg of saw palmetto extract daily for 90 days had lower receptor values for estrogen and progesterone than those in a placebo group. The researchers also found that saw palmetto extract blocks the translocation of the cytosol androgen receptor to the nucleus. The overall implications of the study are that saw palmetto extract has both anti-estrogenic and anti-androgenic effects. A double-blind, placebo controlled study involving 110 BPH patients over 28 days found that saw palmetto administration significantly improved BPH symptoms, such as dysuria, nocturia, prostate volume, and residual urine.
Finasteride has had similar positive effects in the control of BPH but can take up to a year for the effects to occur, whereas saw palmetto generally produces positive effects in as little as 30 days and without serious adverse effects. Saw palmetto does not appear to effect PSA levels. New research has discovered that men treated with saw palmetto had greater improvement in urinary tract symptoms associated with BPH than those who received placebo. A new randomized study of 44 men aged 45-80 years found that men receiving saw palmetto had improvement in symptoms associated with BPH, though this improvement did not reach statistical significance.
A new microbiological study found that the application of an extract of saw palmetto to prostate cells led to increased rates of cell apoptosis. Researchers have found that saw palmetto has effects at the most basic physiologic levels by interfering with the effects of a hormone called prolactin and its stimulation of prostate cell proliferation. A different group of researchers isolated a component of saw palmetto called myristoleic acid that induces cell death in the LNCaP line of prostate cancer cells. Another study found that an extract of saw palmetto inhibits the activity of an enzyme that is important in the development of prostate cancer. An extract of saw palmetto has been found to inhibit the activity of another enzyme called cyclooxygenase-2, which has been implicated in the progression of prostate cancer. A recent study found that an extract of saw palmetto had equivalent therapeutic effects and fewer side effects as a commonly prescribed medication for prostate enlargement, a risk factor for development of prostate cancer.
Researchers found that saw palmetto has specific effects on mast cell accumulation and epithelium atrophy that may be responsible for its positive effects on prostatic hypertrophy and prostate cancer development. A saw palmetto extract has been found to be inhibitor of the enzyme 5alpha-reductase, which is the key factor in the development of prostate cancer. A different study also found that saw palmetto inhibits 5alpha-reducase in human prostate cancer cell lines without affecting PSA levels.
Bitter Almond (Pygeum Africanum)
Pygeum africanum is an evergreen tree native to Africa. The fatty acids of the extract have similar properties to those of saw palmetto. The tree also contains esters of ferulic acid, which have effects on the endocrine system. Studies have shown that docosanol reduces levels of testosterone and leutinizing hormone. Docosanol is a compound that has been found in Pygeum africanum. Docosanol has been found to reduce prolactin levels in the body. Prolactin increases the uptake of testosterone and increases the conversion of testosterone to DHT in the body. Pygeum contains quantities of docosanol but the esters of ferulic acid have similar activity and are found in greater concentrations and are more bioavailable in pygeum than docosanol. Ferulic acid esters have been shown to reduce the cholesterol content in the prostate. Cholesterol end-products in the prostate have been associated with both BPH and cancer.
The sterolic portion of pygeum also works against the accumulation of testosterone in the prostate. Double-blind studies have found that standardized pygeum extract, like that of saw palmetto, improved a variety of urinary symptoms associated with BPH, such as urinary frequency, nocturia, flow interruption, after-dribbling, weak stream, and hesitation. Pygeum has also been found to increase prostatic secretions and improve the composition of the seminal fluid. Standardized pygeum extract has also been found in double blind clinical trials to improve the capacity of BPH patients to achieve erections. All of these factors suggest a role for pygeum in prostate cancer patients who have received a prostatectomy, and possibly a role in the prevention of disease. A double-blind study found that saw palmetto was more effective than pygeum extract in most measures of BPH, but pygeum has better proven effects on prostate secretion. The standardized extract of pygeum is 14% triterpenes including betasitosterol and 0.5% n-docosanol. The typical dose is 100-200 mg per day in divided doses. The crude herb is not used therapeutically.
New research in rat prostate tissues suggests pygeum africanum extract has positive effects on processes associated with BPH development. An additional study in animal tissues found further evidence of positive effects from pygeum africanum administration on infl ammatory effects associated with the development of BPH. A review of 18 controlled clinical trials involving 1,562 men found that men treated with pygeum africanum for at least 30 days were more than twice as likely as controls to have symptom improvement associated with BPH than those receiving placebo. Researchers have recently isolated an extract of pygeum africanum called V-1326 that may be responsible for its positive effects on prostate enlargement and the inhibition of prostate cancer development. A review of 18 randomized controlled trials found that Pygeum africanum is an effective treatment for an enlarged prostate and may have preventative effects on prostate cancer development. A study in rats found that an extract of Pygeum africanum called Tadenan counteracted many of the harmful physiologic effects of dihydrotestosterone. A different study involving rats found that Tadenan has a variety of physiologic effects that inhibit the proliferation of prostate cells.
Cernilton
Clinicians in Europe have used an extract of flower pollen called Cernilton for more than 35 years to treat prostatitis and BPH. Double-blind clinical trials have shown that Cernilton improved BPH patients at an overall success rate of 70%. Nocturia and diurnal frequency symptoms improve in about 70% of patients. Researchers have found evidence that Cernilton contains a substance that can inhibit the growth of prostate cells. A study of 79 males aged 62-89 evaluated the effects of the administration of 63 mg Cernilton pollen extract daily for 12 weeks. The mean baseline prostatic volume was 33.2 cm.
During the study period, maximum urinary flow rate increased from 5.1 to 6.0 ml/sec. Average flow rates increased from 9.3 to 11 ml/sec. In addition, residual urinary flow rates decreased from 54.2 ml to below 30 ml. Furthermore, all of the following measures improved in these patients: urgency, intermittency, delayed voiding, post-void dribbling, prolonged voiding, incomplete emptying, dysuria, and nocturia. Cernilton demonstrated 50% inhibition on DU145 cell line growth after 2 days exposure at 5 mcg/ml. A recent review of studies involving cernilton for the treatment of BPH found that cernilton modestly improves urologic symptoms associated with BPH.
A review of studies involving cernilton and its effects on prostate enlargement found that cernilton improved urinary symptoms compared to a group receiving Tadenan and a control group in men with this condition. A study of an extract of cernilton called DIBOA found that this compound inhibited the growth of DU-145 prostate cancer cells. An additional study confirmed the inhibitory effects of DIBOA on a prostate cancer cell line. A randomized study of 243 patients with urinary disturbances associated with benign prostatic hyperplasia found that a combination of tamsulosin hydrochloride with cernilton led to significant improvement in urinary symptoms. Urinary difficulties are also a significant problem in prostate cancer patients. A study has also found that cernilton pollen extract protects the epithelial cells lining the prostate, inhibits the proliferation of prostate cells, and enhances apoptosis of abnormal cells.
Urtica dioica (stinging needles)
Urtica dioica has also been found to have beneficial effects in the treatment of BPH. Two double-blind studies have shown it to have greater efficacy in treating BPH than placebo. The range of efficacy in this plant appears to be comparable to that of pygeum. This ranks it lower than saw palmetto for the treatment of BPH and in prostate cancer prevention potential. The effects of Urtica dioica are similar to those of saw palmetto in that its main activity appears to be the interference of dihydrotestosterone binding to both cystolic and nuclear receptors. This suggests a role in the prevention of prostate cancer. A study of 431 patients with BPH found that a combination therapy composed of extracts from saw palmetto and urticadioica was as effective as finasteride in treating the symptoms of disease. A recent study found that a 20% extract of Urtica dioica had significant antiproliferative effects on human prostatic epithelial and stromal cells. Newer research has found the mechanisms produced by Urtica dioica that produce the anti prostate cancer effects. The researchers identified adenosine deaminase inhibition as the key effect in the prevention of prostate cancer cell growth.
Garlic
A compound in aged garlic significantly inhibited the growth of human prostate cancer cells in vitro. A new study has demonstrated that garlic has properties that can detoxify cancer-producing factors. Preliminary studies with allium, a component of garlic, suggest this compound has strong anti-tumor properties in both prostate and breast cancer cells. A different study found evidence that a constituent of garlic called S-allylmercaptocyste has anti-tumor effects in prostate cells by converting the breakdown products of testosterone into less harmful substances.
A review article has cited new evidence for the antiproliferative effects of garlic on prostate cancer. An additional study found further evidence of the ability of garlic-derived allium to inhibit the proliferation of the LNCaP prostate cancer cell line. A case-control study of 328 men diagnosed with prostate cancer found that men who consumed two or more servings of garlic per week had a 44% decreased risk of developing prostate cancer compared to those who never ate garlic. A newer study has found that a compound in garlic called diallyl disulfide inhibits the growth of prostate cancer cells. An additional study found similar results and identified diallyl disulfide as the key factor in the apoptosis (cell death) of prostate cancer cells.
Citrus Pectin
Citrus pectin is a soluble component of plant fiber that is derived from citrus fruit. There is some evidence that citrus pectin can inhibit prostate cell formation and growth. A study in rats found that animals given 1.0% by volume citrus pectin in their drinking water had statistically significant reductions in the metastasis of prostate carcinoma compared to control animals. A study involving mice found that the administration of high-dose(1.6 mg/ml) modifi ed citrus pectin inhibited the tumor size after 20 days compared to controls. A study of cancerous human prostate cells found that the addition of modified citrus pectin to the culture interfered with the mechanisms necessary for the cancer cells to multiply. There is a significant amount of interest in studying modified citrus pectin for its anti-metastatic effects. A newer study found evidence for the first time that modified citrus pectin may reduce the growth of solid primary tumors.
Green Tea
Green tea has been shown to have inhibitory effects on prostate cancer cell growth. Studies in rats suggest that compounds contained in green tea inhibit the activity of 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone, which has carcinogenic effects in the prostate. Researchers have found that the most potent of these compounds is called epigallocatechin-3-gallate (EGCG). A study in rats found that green tea has inhibitory effects on other enzymes associated with the growth of prostate cancer cells. EGCG has been found in high concentrations in the serum of green tea drinkers. EGCG and other compounds in green tea inhibit the activity of the enzyme called proteasome, a key factor in the formation of prostate cancer.
A recent review cited evidence that green tea can inhibit the formation of prostate cancer. A study in rats found that polyphenone-60, an extract of green tea, interfered with an enzyme called aromatase, which is known to be a key factor in the development of prostate cancer. Epidemiological evidence suggests green tea reduces the risk of developing prostate cancer, and a new study suggests green tea provides these protective effects by depleting levels of polyamines, which are an important part of cellular proliferation. A different study found evidence that green tea catechins inhibit some of the conversion of testosterone to dihydrotestosterone. A recent study in mice found that a polyphenolic fraction isolated from green tea not only inhibited localized prostate cancer growth but also inhibited the metastasis of the cancer to distant sites. A different study found that several catechins from green tea suppressed the growth of prostate cancer DU-145 cells.
Spices
Spices add flavor to food but also may have cancer-fighting properties. India has one of the lowest cancer rates in the world, and the people there typically eat a diet containing a wide variety of spices. There is some limited evidence that capsaicin, the component of chile peppers that makes them hot, has some anti-cancerous properties. Both curry and cumin contain turmeric, which has been found to have anti-carcinogenic properties in cell cultures. Research from animal studies in Asia has suggested capsaicin has antitumor effects. A study at Yale University found that capsaicin interferes with the tumor-formation process in mice.
Curcumin
In studies involving mice, curcumin has demonstrated anti-carcinogenic activity in a variety of cancers. While the mechanisms of its action are still unknown, curcumin has also demonstrated anti-carcinogenic effects in human cancer cell lines. A recent study in mice found that curcumin decreased the proliferation of both androgen-dependent and androgen-independent prostate cancer cells. A different study found that curcumin inhibits the growth of prostate cancer cells by inhibiting the enzymatic activity of tyrosine kinase at the epidermal growth factor receptor. A study determined that curcumin has great potential in the treatment of androgen-independent prostate cancer. A recent study found that curcumin inhibited both androgen-dependent and androgen independent prostate cancer cell lines, and accomplishes this by inhibiting the effects of factors called NF-kappaB and AP-1.
Other Agents
A commercial eight-herb formulation called PC-SPES fed to rats in 0.05% and 0.025% levels in the diet led to dose-dependent effects on both tumor incidence and tumor growth rate. PCSPES decreased serum testosterone in six men with prostate cancer. An additional eight of eight patients had reduced PSA levels after using PC-SPES. PCSPES has strong estrogenic activity that could cause adverse effects. A study among 16 men with hormone-refractory prostate cancer led to significant improvement in quality-of-life measures, reduction in patient pain ratings, and decreased PSA levels. Biofeedback therapies can help men with prostate cancer and prostatectomy restore pelvic muscle function. A treatment group regained continence after 51 days compared to 56 days in the control group. Acupuncture was used on 7 men who developed hot flushes after receiving castration therapy for prostate cancer. Six of the men completed 10 weeks of acupuncture therapy and had an average symptom decrease of 70%. A new study of ginseng found that a constituent called ginsenoside Rg3 demonstrated inhibitory action against a human prostate carcinoma cell line.
Evidence suggests licorice root (Glycrrhiza glabra) can decrease circulating levels of testosterone in men. A study has found that licorice root has many similar properties to that of paclitaxel, a commonly used chemotherapeutic drug. This study also provided evidence that licorice root can induce apoptosis in prostate cancer cells.
Source:Prostate Cancer Fund,(a special program of Project Cure Foundation) P.O. Box 96673, Washington, D.C. 20090-6673 • 1-800-716-2152. Photo courtesy of www.meb.uni-bonn.de
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