Dietary data disappoint, but are not the final word

Apr 01, 2006

Benefits are more likely to be derived from a lifetime of dietary discretion rather than a mid-to late-life switch.

An American Heart Association review muted the enthusiasm for soy and its potential to lower cholesterol and the risk of breast and prostate cancer (Circulation 2006; 113:1034-44). A randomized, controlled trial studying the benefits of saw palmetto versus placebo for men with LUTS did not substantiate empirical and prior trial data demonstrating an advantage for saw palmetto in this symptom complex (N Engl J Med 2006; 354:557-66). Even the benefits of antioxidants and omega-3 fatty acid have been questioned (JAMA 2006; 295:403-15; J Natl Cancer Inst 2006; 98:223-5).

This is all disheartening news for those who maintain the conviction that we are what we eat, and for those who have modified their diets to include the more spartan fare of beans, rice, soy burgers, and squash soup sprinkled with broccoli sprouts and curcumin (turmeric). But, as the analysts point out, the conclusions are premature. Benefits are more likely to be derived from a lifetime of dietary discretion rather than a mid-to late-life switch in hope of negating decades of oxidative stress.

Dr. Moyad and Dr. Simoneau make several pivotal points; namely, that more is not always better and, in fact, may be worse; that supplements should be discontinued prior to radiation or surgery; and heart healthy is likely prostate healthy.

Although not mentioned in these articles, the role of vitamin D in prostate cancer is becoming more intriguing. From an epidemiologic standpoint, men living in areas of southern sun exposure conducive to the physiologic production of vitamin D have a lower instance of prostate cancer than those men living in the cloud-covered, shortened daylight hours of the north. The ability to synthesize the activated form of vitamin D decreases with age, and the incidence of prostate cancer increases with age. There is an inverse relationship of serum levels of vitamin D with the incidence of prostate cancer.

In addition, high-dose vitamin D has been shown to modify PSA kinetics. The addition of vitamin D to chemotherapeutic regimens has demonstrated a statistically significant survival benefit and a modifying effect of toxicity (Eur J Cancer 2005; 3[suppl]:232). Finally, recent laboratory evidence has confirmed the in vitro suppression of prostate cancer cell growth by vitamin D.

Until we know more, Dr. Simoneau's admonition of moderation in supplement use, a balanced diet, exercise, and attention to clinical trial information provides the best recommendation.

Dr. Schellhammer, a member of the Urology Times Editorial Council, is professor of urology at Eastern Virginia Medical School, Norfolk.