The study, led by researchers from the Mayo Clinic, is one of the largest and longest ever to examine DHEA's effect on key markers of aging, such as muscle strength and physical performance.
Older men and women who took the steroid hormone for two years showed no measurable improvements in areas including measurements of body fat, physical performance, insulin sensitivity, or quality of life compared with older people given a placebo.
The findings are published in the Oct. 19 issue of The New England Journal of Medicine.
"This research is pretty definitive," researcher K. Sreekumaran Nair, MD, PhD, tells WebMD. "We found no evidence that DHEA has an antiaging effect."
Fountain of Youth?
DHEA (dehydroepiandrosterone), is a hormone that can be converted by the body to the sex hormones testosterone and estrogen. Levels of DHEA are naturally very high among teens and young adults but begin to decrease by the early 30s. The typical 70-year-old has DHEA levels only about 20% as high as he or she had in the early 20s.
The thinking has been that restoring DHEA levels to those that naturally occur in younger adults may help slow the aging process and delay diseases of aging, such as heart disease, diabetes, and cancer.
There is some clinical evidence to back up this claim, including one study published in 2004, which showed reductions in abdominal fat and improvements in insulin sensitivity among older people who took DHEA for six months.
But that study was much smaller and shorter than the newly reported trial, which included 87 men and 57 women aged 60 or older treated with DHEA, low-dose testosterone, or placebo for two years.
DHEA was given at doses designed to restore hormone levels to those typical for men and women in their 20s. The men receiving low-dose testosterone were treated with 5 milligrams per day of the hormone.
Effects of DHEA Treatment
The researchers conclude that treatment with DHEA or low-dose testosterone did not bring out clinically relevant effects on most of the aging markers studied.
DHEA and testosterone did appear to have some positive effect on bone density, but the benefits were much smaller than those typically seen with the most effective bone-strengthening drugs, the Mayo researchers conclude.
"Taken together, our data provide no evidence that either DHEA or low-dose testosterone is an effective anti-aging hormone supplement and argue strongly against the use of these agents for this purpose," they write.
Same Data, Different Take
But a spokesman for the dietary supplement industry has a different take on the findings.
Andrew Shao, PhD, of the Council for Responsible Nutrition, says the two-year study confirms the safety of relatively high-dose DHEA in both men and women. No clinically significant side effects were reported among participants who took DHEA or low-dose testosterone.
"We are encouraged by those results, particularly because there is a need for safe bone builders in this age group," Shao says.
In an editorial published along with the study, Paul M. Stewart, MD, of the UK's University of Birmingham, questioned the safety of DHEA and called for it to be classified as a drug, rather than a dietary supplement -- which is not strictly regulated by the FDA.
"Appropriate regulation would dispel much of the quackery associated with this elusive hormone," he writes.
Aging and longevity researcher Peter Hornsby, PhD, agrees. The University of Texas Health Science Center professor of physiology tells WebMD that DHEA should never have been classified as a dietary supplement.
"There is no logical reason why a steroid hormone should be considered a supplement," he says. "Yo can't have it both ways. If this is a real steroid hormone, it should not be taken without a doctor's supervision, just like estrogen and testosterone."
SOURCES: Nair, K.S. The New England Journal of Medicine, Oct. 19, 2006; vol 355: pp 1647-1659. K. Sreekumaran Nair, MD, PhD, division of endocrinology, Mayo Clinic, Rochester, Minn. Peter Hornsby, PhD, professor of physiology, University of Texas Health Science Center, San Antonio. WebMD Medical News: "Hormone Protects Against Diseases of Aging." Andrew Shao, PhD, Council for Responsible Nutrition. Paul M. Stewart, MD, University of Birmingham, Queen Elizabeth Hospital, Birmingham, England.
By Salynn Boyles
Reviewed by Louise Chang