DHEA supplements have no effect on aging markers, says study
DHEA does not have "physiologically relevant beneficial
effects" on markers for anti-aging - a finding that does not
help the industry's fight to preserve the hormone precursor's
status as a dietary supplement.
Indeed, results of the study, published in the highly respected New England Journal of Medicine (Vol. 355, pp. 1647-1659), have led some in the medical profession to call for the hormone to stop being labeled as a dietary supplement and be treated as a regulated drug.
Despite the apparent negativity, dietary supplements industry trade association, the Council for Responsible Nutrition (CRN) said in a statement that they were "encouraged" by the results, and pointed out the new data showing small but significant positive effects on bone mineral density and the good safety data.
DHEA (dehydroepiandrosterone) - a precursor to the hormone testosterone - occurs naturally in the blood of young people. Levels have been shown to peak between the ages of 20 and 30 years, but decrease progressively thereafter.
Dietary supplements containing DHEA (derived from a plant in the wild yam family) have been available in the US for more than 20 years, and sales are reported to have hit $50m last year. The anti-aging benefits are said to include aiding cognitive function, mood enhancement and stress disorders, as well as fighting viral infection and suppressing chronic inflammation.
But results of the two-year, placebo-controlled, randomized, double-blind study from the Mayo Clinic call into question the anti-aging benefits of the supplement.
"For almost two years we restored DHEA in older men and women to the high normal levels that are usually observed in young people, but found no beneficial effects on age-related changes in body composition and function," said the study's lead author K. Sreekumaran Nair, M.D. "No beneficial effects on quality of life were observed. There's no evidence based on this study that DHEA has an anti-aging effect."
The researchers recruited 87 men (average age 67) and 57 women (average age 69) to take part in the study. The men were assigned to one of three supplement groups: DHEA tablet (75 mg per day), testosterone patch (5 mg per day), or placebo. Women were assigned to either the DHEA supplement (50 mg per day) or placebo.
The primary outcomes of the study were body composition, physical performance, bone mineral density, peak aerobic capacity, and plasma glucose and insulin levels.
The researchers did not measure other potentially relevant outcomes where DHEA has been reported to provide benefit, such as libido and sexual performance, or mortality risk.
Dr. Nair and co-workers report that, after two years, no significant changes in body composition, physical performance, insulin sensitivity or quality of life, were found.
Bone mineral density measurements of the femoral neck (hip) did increase by a small but significant amount (0.02 grams per sq. cm) in men taking DHEA, report the researchers, but no significant improvements were observed at the four other skeletal sites studied.
In women taking the DHEA supplements, a small but significant increase (0.02 grams per sq. cm) in the ultradistal radius (forearm), but no significant improvements were observed at the four other skeletal sites studied.
However, these results are downplayed by the researchers: "Since other well-tolerated and tested pharmacological agents result in a far greater increase in BMD, the value of DHEA for either preventing or treating osteoporosis in elderly men and women is probably limited," wrote Nair.
The Mayo study was supported by grants from the National Institutes of Health, by the Department of Medicine, Mayo Clinic, and the Mayo Foundation. Two of the 18 researchers disclosed previously receiving fees from large pharmaceutical companies.
In an accompanying editorial (NEJM, Vol. 355, pp. 1724-1726), Dr. Paul Stewart from the University of Birmingham in the UK, said that this "'negative' study on the efficacy of DHEA is unlikely to have much effect on its use in Western societies. Owing to a loophole in US legislation, DHEA is not regarded as a drug but, rather, as a dietary supplement."
Stewart said that, without changing the regulations, DHEA would continue to be used "inappropriately, and the quackery will prevail."
"Establishing the hormone's safety or lack thereof might lead to the reclassification of DHEA as a drug, since supplements are defined as causing no harm," he said.
However, the Mayo researchers reported that, from a safety point of view, neither DHEA nor testosterone were found to cause any "detectable harm".
"This finding of safety is the most important outcome of this study, and should not be discounted," said the CRN in a statement.
The CRN's Andrew Shao, PhD., said: "This is the longest duration human supplementation trial confirming the safety of relatively high-dose DHEA in both men and women and we are encouraged by those results, particularly because there is a need for safe bone builders in this age group.
"Further, the study found small but significant increases in bone mineral density, consistent with the body of clinical trials on DHEA. The lack of other significant effectsin an elderly population is surprising as that is inconsistent with the published research.
"This study did not look at other clinically relevant outcomes where DHEA has been to shown to provide benefit, such as libido and sexual performance," he said.
