This forthright condemnation came in the wake of a two-year-long study of this steroid hormone by a group of doctors from America's celebrated Mayo Clinic, in Rochester, Minnesota. Based on their results, they concluded that DHEA has no "physiologically relevant beneficial effects on body composition, physical performance, insulin sensitivity, or quality of life" (N Engl J Med, 2006; 355: 1647-59).
This declaration led some alter-native practitioners who prescribe DHEA for their patients to respond somewhat vehemently. "I have used it extensively in clinical practice," declares American pracitioner Dr Alan Gaby, "and I am firmly convinc-ed that DHEA is highly beneficial for selected individuals."
The evidence for longevity
If DHEA is a sort of elixir of youth, will it make you live longer? Sadly, the answer is not clear-cut.
On the plus side, the evidence is fairly conclusive that the more DHEA you have in your bloodstream, the longer you'll live.
The most recent study, carried out by researchers at the University of California at Berkeley, tracked the death rates of nearly 1000 elderly Taiwanese men for three years. They found that those who had low levels of DHEA (less than 54.5 mcg/dL) had more than a 60 per cent greater chance of dying before the men who had higher DHEA levels.
Similar findings have been made among different Western racial populations (Ann Epidemiol, 2006; 16: 510-5).
The obvious implication from these data is that taking DHEA supplements should prolong life-although, curiously, this possibility doesn't appear to have been clinically investigated.
Belgian scientists recently sifted through the medical and scientific literature for studies of DHEA supplementation and mortality, but found none that were of a high-enough scientific standard to enable any firm conclusions to be drawn (Endocr Rev, 2005; 26: 833-76).
Giving DHEA to lab animals does appear to prolong life, but rats and mice have a totally different DHEA physiology from humans, so such findings are not likely to be relevant (Trends Endocrinol Metab, 2002; 13: 288-94).
Treating other conditions
The value of DHEA for treating a number of conditions is nevertheless well established. The most important of these is Addison's disease, a condition that attacks the adrenal glands, thus reducing the body's own natural supply of DHEA. Taking 50 mg/day of DHEA has been shown to improve bone and skin health, sex drive and overall quality of life-at least in older patients with Addison's disease (Rev Med Suisse Romande, 2001; 121: 649-54).
Depression is another potential DHEA target, as the hormone is thought to have an effect on brain cells. A recent study, carried out by doctors at the National Institute of Mental Health (NIMH) outpatients clinic in Bethesda, Maryland, tested
a group of nearly 50 middle-aged people diagnosed with depression. The DHEA supplements were given in two stages: 90 mg/day for the first three weeks, which was ramped up to 450 mg/day for the next three weeks.
This regime resulted in a 50-per-cent reduction in symptoms com-pared with a placebo, and a corres-ponding improvement in sexual functioning.
"We find DHEA to be an effective treatment for midlife-onset major and minor depression," the authors reported (Arch Gen Psychiatry, 2005; 62: 154-62).
Although a handful of other studies has shown similarly positive overall results, the precise mech-anism of action of DHEA in treating depression remains a mystery. One theory is that it may be affecting serotonin in the brain, while another is that it could be reducing the effect of stress hormones (World J Biol Psychiatry, 2001; 2: 115-43).
DHEA is often touted as a mental enhancer-particularly for the elderly-although there's no clinical evidence to support such a claim. Researchers at the University of Oxford recently reviewed all of the medical literature on the subject, and concluded that, based on the current evidence, DHEA appears to have little value for improving mental functioning in the old and middle-aged. However, they also reported that the subject merits further study (Cochrane Database Syst Rev, 2006; 4: CD006221).
DHEA and ageing
What about the other effects of growing old?
Muscle loss is a major cause of frailty in the elderly, and DHEA is often claimed to arrest it.
The evidence, however, is not convincing. A clinical trial published within the last six months has shown that taking DHEA supplements is only beneficial when it's combined with weight training. If you do nothing else physically to improve your muscles, then taking DHEA alone won't stop them from diminishing (Am J Physiol Endocrinol Metab, 2006; 291: E1003-8).
A related issue is bone strength, which also diminishes with age. As this-and bone loss or osteoporosis (bone-thinning)-are known to be hormone-related, can DHEA help here, too?
Happily, in this case, the answer is yes. A new study has clearly shown that after a year of taking DHEA supplements, bone mineral density was significantly improved in the hip and spine (J Clin Endocrinol Metab, 2006; 91: 2986-93). There is also 'promising' evidence that DHEA may help to prevent and treat osteoporosis (Ann Pharmacother, 2006; 40: 836-49).
Another consequence of ageing is what's known as 'metabolic syndrome' or 'syndrome X'. This condition is very common in old age, manifesting itself as an increase in fat around the midriff-the classic 'spare tyre'. This is thought to be related to a decrease in sensitivity to insulin, leading to excess glucose being laid down as fat. In these cases, DHEA has proved to be rather effective, according to a recent placebo-controlled trial involving a small group of people aged from 65 to 78. After taking DHEA supple-ments for just six months, they lost an average of almost 5 square-inches of fat from their waistlines (JAMA, 2004; 292: 2243-8).
It's worth pointing out, however, that for every study showing a benefit from taking DHEA, there are just as many that don't. In general, however, the more modern the study, the more likely it is to show a positive effect, although only Addison's disease and depression can claim universal agreement of benefit from DHEA.
Neverthess, the latest Mayo condemnation may have been unduly severe. The small print of its study data reveals that there were some beneficial effects of DHEA supple-mentation that the authors simply chose not to highlight-but which confirm the findings of other researchers. Albeit small, the Mayo study did find increases in bone mineral density and decreases in abdominal fat, for example.
One other possible confounding factor was that all the experimental subjects were fairly healthy-and it's already known that DHEA won't do you much good if there's nothing wrong in the first place (Best Pract Res Clin Endocrinol Metab, 2004; 18: 363-80).