Nutrition and Prostate Health: What's the latest?

Prostate cancer is the second most frequently diagnosed cancer in US men. Age is a factor in the development of this cancer: most cases are found in men over the age of 55. Hormones, including testosterone may play a role. Also, some families have a higher incidence of prostate cancer, suggesting inherited susceptibility may influence this disease. However, when people from areas with low prostate cancer rates move to areas with high rates, they tend to adopt the rates of their new environment. This suggests that environmental factors may play an even bigger role than genetic factors. There is, in fact, increasing evidence that diet is one of those important factors, and a number of studies are in progress to help identify possible dietary strategies for prevention.

Vitamin E and Selenium

One such large-scale study, called the Selenium and vitamin E Cancer Prevention Trial or SELECT, is being launched by the National Cancer Institute (NCI). The NCI is seeking 32,000 healthy men 55 and older to determine if these two nutrients, both separately and together, can protect against prostate cancer over a twelve-year period (1).

Vitamin E and selenium were chosen for study because of the result of two other large prevention trials. In one, selenium was reported to decrease the incidence of this cancer (2). In another trial, in which vitamin E and beta-carotene were tested to prevent lung cancer in Finnish smokers, those who took vitamin E had significantly less prostate cancer (3).

Vitamin E and selenium are antioxidant nutrients, capable of neutralizing free radicals that might otherwise damage the genetic material of cells and possibly contribute to cancer development. Recently, Stanford researchers observed that low plasma levels of selenium are linked to a higher risk of prostate cancer (4). A new study suggests that vitamin E might also help suppress the expression of hormone receptors in prostate cancer cells (5).

Lycopene, Soy, and Dietary Fat

A member of the carotenoid family, lycopene is found in red-orange fruits and vegetables - particularly tomatoes. A number of observational studies suggest that a higher intake of tomatoes and tomato products may be associated with a reduced risk of prostate cancer (6,7). It's also possible that other phytochemicals or nutrients in tomatoes may contribute to their health benefits, so additional studies are needed to clarify the potentially protective role of lycopene.

A higher intake of soy foods have also been linked to a lower risk of prostate cancer (8). These, and other preliminary findings have led to further investigations. For example, cancer researchers are currently studying whether a greater daily soy intake among patients with early stage cancer can reduce prostate-specific antigen or PSA-an indicator used to test for cancer and measure its severity (9).

If fruits, vegetables and soy foods hold promise for promoting prostate health, a high fat diet may be risky. While numerous studies over the past decade have suggested that reducing dietary fat might help prevent prostate cancer, several recent prospective studies suggest that the impact of fat reduction may be relatively modest (10). Researchers are now trying to determine whether a low fat diet may influence the progression of established tumors (11).

Go For a Healthy Diet

While there's still no definitive answer on whether diet can prevent prostate cancer or slow its progression, there's every reason to consume a diet that's consistent with current guidelines to lower the risk of heart disease and many types of cancer. That means eating a diet that's low in fat and high in fruits and vegetables, including ample amounts of whole grains and legumes (nuts, seeds and beans such as soy). Since cancer is not a single event, but the result of a long process, it's a healthy diet over the long term that really counts.

References

1. Cancertrials.nci.nih.gov (National Cancer Institute)
2. Clark LC et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. JAMA 26:1957-63, 1996.
3. Heinonen OP et al. Prostate cancer and supplementation with alpha-tocopherol and beta-carotene: incidence and mortality in a controlled trial. J Natl Cancer Inst 90:440-6, 1998.
4. Brooks JD et al. Plasma selenium level before diagnosis and the risk of prostate cancer development. J Urol 166:2034-38, 2001.
5. Zhang Y et al. Vitamin E succinate inhibits the function of androgen receptor and the expression of prostate-specific antigen in prostate cancer cells. Proc of Natl Acad Sci 99:7408-13, 2002.
6. Giovannucci E et al. A prospective study of tomato products, lycopene, and prostate cancer risk. J Natl Cancer Inst 94:391-8, 2002.
7. Miller EC et al. Tomato products, lycopene and prostate cancer risk. Urol Clin North Am 29:83-93, 2002.
8. Aldercreutz H. Review: phyto-estrogens and cancer. Lancet Oncol 3:364-73, 2002.
9. www.moffitt.usf.edu (H. Lee Moffitt Cancer Center)
10. Moyad MA. Review. Fat reduction to prevent prostate cancer: waiting for more evidence? Curr Opin Urol 11:457-61, 2001.
11. Demark-Wahnefried W et al. Pilot study of fat restriction and flaxseed supplementation in men with prostate cancer before surgery: exploring the effects on hormonal levels, PSA, and histopathologic features. Urology 58:47-52, 2001.