"This product is touted everywhere like it's the fountain of youth," said Donna Kritz-Silverstein at the University of California at San Diego School of Medicine and lead author of the report.

"But when we looked @ ... cognitive function, mood, sexual function and feelings of general well-being, it didn't seem to provide any benefit," said Kritz-Silverstein, whose study was published in the May issue of the Journal of the American Geriatrics Society. The National Institute on Aging funded the research.

The body's adrenal glands make DHEA, or dehydroepiandrosterone, out of cholesterol. DHEA is then converted into two important hormones - testosterone and estrogen.

DHEA production declines gradually during life, starting when people are in their mid-20s. By the time individuals reach 70, their DHEA levels are about one-fifth of the peak.

Consumer interest in DHEA supplements took off in the 1990s, and U.S. sales of the product totaled about $55 million last year. It costs nearly $100 for a year's supply of pills that amount to 50 mg a day, the amount required to achieve peak levels of DHEA in the bloodstream.

Studies on the effects of DHEA have been limited, and their findings have been mixed.

"There is little scientific evidence to support the use of DHEA as a 'rejuvenating' hormone," the National Institute on Aging said on its Web site.

The agency also said early signs suggest that DHEA supplements might cause problems such as liver damage and raise the risk of breast and prostate cancer by adversely influencing levels of testosterone and estrogen.

In the 1990s, some studies found that mice and rats showed greater learning and memory capacity after receiving doses of DHEA.

"That prompted some people to speculate that if you could restore DHEA levels to that of youth, perhaps you could improve health overall," Kritz-Silverstein said.

In recent years, certain studies recorded no benefits from DHEA supplements.

Others suggested that people who receive boosts of DHEA have improved libido and memory skills. But Kritz-Silverstein said those studies weren't definitive because they tested DHEA supplements for only a few weeks or months, enrolled very small numbers of participants and didn't focus on people old enough to start suffering age-related cognitive impairment.

"So the only way to determine whether they have any benefits is to conduct good, scientific, placebo-controlled clinical trials to see if they work," she said.

The University of California San Diego study enrolled 225 healthy men and women in the San Diego area ages 55 to 85. Half of them took 50 mg of DHEA pills per day, while the other half took placebo pills.

Participants were examined for depression, perceptions of physical and emotional health, satisfaction with life and sexual function throughout the study. When the results were tallied, "We really didn't see any change over the year between those who were taking DHEA and those who were not," Kritz-Silverstein said.

Dr. Thomas Perls, a specialist in the anti-aging industry at the Boston University School of Medicine, said claims that DHEA supplements rejuvenate healthy seniors are a "sign of medical quackery."

While there might be limited benefit in giving DHEA supplements to younger people with conditions that cause abnormally low DHEA levels, he said, "I'm not familiar with any studies showing a beneficial effect on young or old individuals aging normally."