DHEA has long been touted as an anti-aging therapy, used to ward off chronic illness and maintain energy and vigor. However, an October 2006 study published in the New England Journal of Medicine has found no evidence that taking DHEA reverses the effects of aging.

Here, K. Sreekumaran Nair, M.D., an endocrinologist at Mayo Clinic, Rochester, Minn., and an author of that study, answers questions about DHEA.

DHEA, or dehydroepiandrosterone, and its sulfated form DHEA-S are the most abundant naturally occurring hormones circulating in the human body. Like other hormones, DHEA and DHEA-S help to regulate various body functions.

DHEA is secreted by the adrenal glands located on top of your kidneys. DHEA levels reach their peak by the time you're in your 20s and then decline with age. Its physiological role isn't completely understood, but it is known that DHEA can be converted by the body into testosterone and estrogen. These two hormones play many important roles throughout life.

The decline with age of DHEA levels correlates with many age-related changes, including loss of muscle mass, decrease in bone density and decline in the immune system's ability to fight disease. An association of DHEA levels with longevity has been reported both in primates and humans. However, no experimental data is available to show that maintaining the high DHEA levels found in young people prolongs life. When given to rats, DHEA prevents many age-related changes. But unlike humans, rats have very low DHEA to begin with. Some short-term studies have shown tantalizing evidence that suggest beneficial effects from DHEA.

We looked at whether DHEA administration has any beneficial effects on body composition — muscle mass, fat and fat-free mass, and abdominal fat. We also evaluated the possible effect on muscle strength in both the upper and lower extremities, on peak VO2 (a measure of your physical endurance limit), on mineral density of different bones, on glucose tolerance and insulin sensitivity, and on the physical and mental components of quality of life. When we gave some of the study participants DHEA for two years, it showed no physiologically significant beneficial effects on any of those factors in men and women in their 60s and 70s. All these parameters are known to change with age.

To our best knowledge, no other studies have been done that used the high-replacement doses of DHEA used in our study. In addition, no other studies examined DHEA use for such a long period.

Currently, DHEA is extensively used as an anti-aging nutrient supplement and its use isn't regulated by the Food and Drug Administration. It is extensively used by older people with a hope that it may prevent age-related decline in body functions. Although we didn't observe any adverse effects in the study population, we excluded people with cancer, heart disease and prostate problems. The adverse effect of its long-term use in the general population is uncertain. This study clearly indicates that there is no scientific reason for using DHEA as an anti-aging drug.

Don't take DHEA to prevent, delay or reverse any of the aging-related changes in your body. If you are taking DHEA for these reasons, you're urged to stop taking it. If you plan to take DHEA, don't take it. DHEA has no proven beneficial effect, and its possible adverse effects are uncertain.