Prostate Cancer Prevention - Does It Really Work?
Prostate cancer kills over 40,000 Americans each ear. It has been estimated that all men would develop prostate cancer eventually, if they would live long enough. Is prostate cancer prevention possible? What is the value of vitamin E, lycopene, selenium and other dietary factors in prostate cancer prevention? What about the so-called prostate cancer prevention trial?
Cancer Prevention Primer
Prostate cancer is just one of many types of cancer. To a significant degree, what works in preventing cancer in general should work for prostate cancer, too. Before reading the rest of this article, I strongly encourage you to read our
cancer prevention diet article. It will help you develop a broader view on diet and cancer prevention.
What Works For Prostate Cancer Prevention?
Diet and Prostate Cancer Prevention
Although it is very likely there are many dietary factors that may have protective effects against prostate cancer, current data provide evidence for seleniu, vitamin E and lycopene.
Selenium and Prostate Cancer Prevention
Selenium is an essential trace element. It is present in foods in rather small quantities, with the notable exception of Brazil nuts. Other foods relatively rich in selenium are whole grains, fish, poultry, eggs and diary products. It should be noted that selenium concentration in foods displays a significant geographical variability, due to differences in selenium content of soils from different regions of the world. An alternate source of selenium are the numerous types of over-the-counter supplements that contain it.
Selenium's relationship with cancer prevention is likely to be related to its role as a co-factor in enzymatic systems with antioxidant functions throughout the body. There is strong evidence that selenium works by inhibiting critical steps in early cancer formation, promoting death of cancerous cells and modulation of certain genes susceptible to regulation by androgen hormones.
Results from the
Nutritional Prevention of Cancer Trial, selenium supplementation in the form of selenized yeast has been associated with a two-thirds reduction in prostate cancer after 4.5 years of follow-up of over 1,300 participants. In terms of cancer prevention, this is a HUGE effect. The study stirred up the interest of researchers and a new study, investigating the protective effects of selenium (and vitamin E) for prostate cancer is underway. The study is called
Selenium and Vitamin E Cancer Prevention Trial - (SELECT), sponsored by the National Cancer Institute, with final results anticipated in 2013.
Vitamin E and Prostate Cancer Prevention
Vitamin E is a fat-sluble vitamin with important antioxidant functions. It exerts its effects in cell membranes, lipoprotein particles (preventing the oxidation of cholesterol, for example), etc. The most active form of vitamin E is α-tocopherol.
Food sources of vitamin E are whole grains and wheat germ oil, almonds, seeds, seed oils (like sunflower oil), hazelnuts, peanuts, etc.
While vitamin E's prostate cancer prevention effects are less well understood than those of selenium, there are indications that one part of vitamin E's molecule has a direct antiandrogenic activity. Androgens are directly involved in prostate cancer development.
As in the case of selenium, the prostate cancer protective effects of vitamin E came initially from a study designed to investigate another cancer. The study was called he Alpha-Tocopherol, Beta-Carotene Cancer Prevention Trial (ATBC) and it was a large-scale, randomized, double-blind, placebo-controlled trial with over 29,000 male participants, aged 50-69 years, smokers. Researchers were interested to see if α-tocopherol and β-carotene - alone or in combination - would protect these smokers against lung cancer. The surprising finding was that in those who were given vitamin E in the form of 50 mg synthetic dl -α-tocopheryl acetate daily experienced a 32 percent reduction in prostate cancer incidence and a 41 percent lower mortality! Again, these are big numbers when we talk about cancer prevention...
Lycopene
Lycopene is an isomer of β-carotene. The primary food sources of lycopene are tomatoes and
tomato-derived products, as well as other red fruits and vegetables.
The antitumor activity of lycopene is due to its powerful antioxidant activity. While pure lycopene supplementation does not seem to have a great impact on prostate cancer reduction, a diet rich in tomatoes seems to work. There is a need for more studies to ascertain the exact magnitude of the protective effect of lycopene against prostate cancer
Soy
Soy-based diets have been noted to have anti-cancer effects in a number of studies. For example, according to the
Adventist Health Study, frequent consumption of soy milk (at least daily) is associated with a 70% reduction in the risk of developing prostate cancer.
Other Dietary Factors With Possible Protective Action Against Prostate Cancer
- Vitamin D. At least one study has indicated that reduced levels of active vitamin D result in a higher incidence of and a higher mortality rate from prostate cancer. In contrast, native Japanese men, whose diet is rich in vitamin D derived from fish, have a low incidence of prostate cancer. Vitamin D seems to act by inhibiting the proliferation of prostate cancer cells,
- Green Tea. Based on ovservations that the incidence of prostate cancer among native Asian men with a high dietary intake of green tea is low, further research has indicated that the major polyphenolic constituent of green tea inhibits cell growth, and thus may exert a protective effect against prostate cancer.
Non-Dietary Factors and Prostate Cancer Prevention
Finasteride (Proscar) and Prostate Cancer Prevention
Proscar is a drug that inibits one of the final steps in the synthesis of androgen hormones. Since androgens are involved in prostate cancer development, a large study (the
Prostate Cancer Prevention Trial) has investigated the possible protective effect of this drug against prostate cancer. Although the study found finasteride reduced the risk of prostate cancer by approximately 10 percent, its use in prostate cancer prevention is still controversial as it also seemed to increased risk of high-grade (i.e. aggressive) disease in those who developed prostate cancer.
Dr Gily
