Nutrition Action Healthletter
May 1998 — U.S. Edition

An update of articles from past issues of Nutrition Action Healthletter: SECOND HELPINGS

Remembering Ginkgo & DHEA

Ginkgo Biloba

"Taken as directed, Ginkoba can help you remember where you put things," boasts the company's World Wide Web site (

"Clinically verified to improve memory and concentration," claims Ginkai's label.

In our May 1997 article on memory ("Fear of Forgetting"), we pointed out that there's no good evidence that the herb ginkgo biloba helps improve the memories of healthy people, despite the bold claims in ads and on labels.

That evidence is still missing. But last October the media was buzzing with news that ginkgo could help people suffering certain kinds of dementia. Researchers at the New York Institute for Medical Research in Tarrytown, New York, reported that 120 mg of a ginkgo extract each day for six months to a year improved the thinking ability and daily functioning of some people suffering from Alzheimer s disease or from dementia due to strokes.1

Of 155 people given EGb -- available in the U.S. and Canada as Ginkgold -- half scored slightly better on tests that measure memory, language, and orientation than they scored when they entered the study. Only 29 percent of the 154 people given a (lookalike but ginkgo-free) placebo showed the same improvement.

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But some researchers aren't wowed by the results.   "This is a seriously limited and flawed study," says Steven Ferris, director of the Alzheimer's Disease Research Center at New York University.   "The improvements seen in the ginkgo-taking group were so slight that the clinicians who were taking care of the Alzheimer's patients didn't even notice any changes." And more than half of the people who started the trial dropped out before it ended, he adds, which could have exaggerated ginkgo's impact.

Then again, the world isn't exactly awash in Alzheimer's treatments. In a 1997 clinical trial, 1,000 IU of vitamin E twice a day slowed the progression of Alzheimer s.2  But it didn t stop or reverse the disease.

"This fall, a three-year study will start testing vitamin E on people at very high risk of developing Alzheimer's," says Ferris.

-- David Schardt

1 J. Amer. Med. Assoc. 278: 1327, 1997.

2 New. Eng. J. Med. 336: 1216, 1997.


Want something that can prevent heart disease, cut the risk of cancer, rejuvenate your sex life, and postpone aging? DHEA is the answer, according to a chorus of books, magazine articles, and supplement companies.

In our March 1997 article ("DHEA Not Ready for Prime Time"), we pointed out that none of the claims had been substantiated by good research. We also cautioned that the body converts DHEA into testosterone, a hormone that can stimulate the growth of prostate cancer.

dhea-may.jpg (100961 bytes)

Since then, two trials testing DHEA in humans found no significant benefits, though both were small and brief.  What's more, several DHEA experts are now urging caution.

Proponents say that taking DHEA produces a sense of well-being. Yet, in one of the two new studies, 50 mg a day for two weeks produced no measurable psychological changes in 40 healthy older men and women compared with when they were taking a placebo.1

In the other, 36 seniors who took 50 mg of DHEA just before being given a flu shot did not produce any more flu-fighting antibodies than 35 seniors who were given a DHEA-free placebo.2

Meanwhile, Ray Sahelian, a California physician who edits a DHEA newsletter, reports that he has heard of 30 cases of heart palpitations or irregular heartbeats in people taking DHEA and/or another hormone, pregnenolone.

Until more research is done, he says, "I do not recommend more than 10 mg a day of DHEA unless you are very closely monitored by a healthcare professional familiar with these hormones."

Samuel Yen, the University of California at San Diego endocrinologist whose trials are often cited by DHEA proponents, goes even further:   "I strongly discourage the use of over-the-counter DHEA."

-- DS

1 J. Clin. Endocrin. Metab. 82: 2363, 1997.

2 J. Clin. Endocrin. Metab. 82: 2911, 1997.

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Nutrition Action Healthletter