Two hormones available over the counter, melatonin and Dehydroepiandrosterone (DHEA), have become the focus of the escalating--and increasingly controversial--search for the secret of eternal youth. Research on both hormones has shown considerable promise in the prevention and perhaps even reversal of such age-related diseases as cancer, heart disease, diabetes, arthritis, osteoporosis, and even Alzheimer's disease. Users of both substances have also reported improved sleep, memory, mood, and energy levels. 'By restoring levels of the two hormones to their youthful peaks, people may be able to add up to 30 healthy years to their lives,' reports Burkhard Bilger in The Sciences (Sept./Oct. 1995).

Melatonin is a natural sleep-inducer synthesized by the brain's pineal gland. DHEA, one of many hormones produced by the adrenal glands, turns into either estrogen or testosterone--whichever the body needs at the moment--and also has properties independent of either of these sex hormones. As we grow old, we manufacture fewer and fewer of these vital hormones, and some evidence suggests that this slowdown may speed the aging process. There's also some evidence that the converse may be true.

According to a 1993 study conducted by Italian scientist Walter Pierpaoli, old mice receiving either hormone soon looked and acted about half their age and greatly surpassed their life expectancies. Amid the media hoopla that followed this discovery, an important footnote was overlooked: The anti-aging effects kicked in only after the mice were a year and a half old, the equivalent of about 45 to 50 human years. If you're young and wish to slow down the aging clock, you may want to wait a few decades before you start taking melatonin. Timing may be of the essence for DHEA as well. Most researchers advise against taking it before age 50.

Those aren't the only caveats. Some scientists claim that raising the melatonin level could trigger a drop in the pineal gland's production, or reduce the number of 'melatonin receptors' on body cells. Either way, the body's ability to produce or use melatonin could become limited over time. This phenomenon, termed 'down regulation,' was first observed in melatonin-injected lab animals in the 1960s by researcher Russel Reiter, co-author of Melatonin (Bantam, 1995), who is troubled by the recent melatonin craze. 'Frankly, the idea that so many people are now taking melatonin is a bit unsettling to the scientific community,' he told Natural Health (March/April 1996).

Similar concerns have been aired regarding long-term use of DHEA. It is among the most ubiquitous hormones, and DHEA receptors are found on many types of body cells. 'I was astounded that there were physicians out there giving this drug to thousands of people in the absence of any studies about what it does,' Dr. Elizabeth Barrett-Connor told The Sciences. Her own research found that high blood DHEA-sulfate levels reduced the risk of heart disease in men, but seemed to increase it in women. Other side effects may include masculine hair growth, acne, and a receding hairline in women. Postmenopausal women with low estrogen levels who take DHEA appear to be at an increased risk of breast cancer, according to The Lancet (May 13, 1996). (In contrast, younger women who take DHEA actually appear to be protected against breast cancer.) A substantial number of lab animals on DHEA have developed liver cancer, though it's still not clear what these findings mean for humans.