Leaf extracts from one of the world's oldest trees, the ginkgo, can be found in breakfast cereal, tea and tablets sold at supermarkets and health food stores. Marketers claim it can help your memory, but scientists don't agree on whether the herbal product can actually give your brain a boost.
Researchers have been studying ginkgo as a potential "smart drug" for healthy people. They want to know if it improves memory skills or slows the deterioration of mental skills among people with mild cognitive impairment or Alzheimer's disease. They're also interested in whether it can prevent disease altogether.
Recently, a study published in the Journal of the American Medical Assn. raised new questions about benefits for healthy people. Researchers found that a common brand of ginkgo did nothing to sharpen memory, concentration or learning in healthy elderly volunteers a blow to the claims of some supplement companies that ginkgo can "enhance" focus and improve memory in just weeks.
But that's hardly the last word about a popular supplement with annual worldwide sales of more than $500 million. The study was sharply criticized by the supplement industry, and some health professionals, who contended that other U.S. and foreign studies have demonstrated positive effects.
The study compared more than 100 elderly volunteers who took 120 milligrams of ginkgo a day with a similar number of volunteers who took a placebo. Neither the subjects nor researchers knew who got the ginkgo. After six weeks, those who took the product, Ginkoba, scored no better on 14 different tests of mental ability than the placebo group.
Steven Ferris, executive director of the Silberstein Institute for Aging and Dementia at New York University, praised the study, saying it realistically demonstrated the experience of people who might purchase ginkgo and follow the label instructions.
Some proponents of ginkgo criticized the study. Los Angeles psychiatrist Hyla Cass, who often recommends ginkgo to patients because of its potential antioxidant effects on the heart and brain, said study subjects should have been given higher doses for longer periods.
But researchers selected the dosage based on manufacturer instructions and recommendations from Germany's Commission E, a regulatory agency that reviews the effectiveness of herbal medicines, said the study's lead author, Paul Solomon, who also wanted to test the manufacturer's claim of results in four weeks.
"One study never allows people to draw conclusions about how they ought to behave in terms of their health," said Solomon, a psychologist at Williams College in Williamstown, Mass., and at the Memory Clinic at Southwestern Vermont Medical Center in Bennington. "On the other hand, we think this is the most rigorous study done to date."
Solomon, who conducts clinical trials of Alzheimer's medications, became interested in ginkgo because some of his patients wondered if it did any good.
Elderly may benefit
The answer is complicated. Many doctors report anecdotal improvements among patients with memory complaints.
Jerry Cott, former chief of the psychopharmacology research program at the National Institute of Mental Health, wasn't surprised Solomon didn't see effects on normal memory "because these effects are very hard to find." But he noted that researchers Joseph Mix of Liberty University in Lynchburg, Va., and W. David Crews Jr. of Virginia Polytechnic Institute and State University in Blacksburg, Va., have found improvements in healthy older subjects taking 180 milligrams daily for six weeks. They published those findings online last month in the journal Human Psychopharmacology.
Dr. Lon Schneider, a professor of psychiatry, neurology and gerontology at the University of Southern California, said he wished Solomon's study had measured how quickly subjects processed information, because that skill often declines first in seniors. That skill improved among ginkgo recipients in the Mix and Crews studies.
Schneider said Solomon's study of healthy people excluded typical ginkgo buyers, including those with some depression, anxiety, aches and pains in sum, "the people we all seem to know."
Scientists continually debate published findings on ginkgo in healthy and memory-impaired people. Ginkgo supporters cite a 1997 medical association study that found some improvements in Alzheimer's patients; critics said it didn't demonstrate significant benefits.
Schneider was the lead investigator in a 500-person study to determine whether ginkgo can help people with mild to moderate Alzheimer's. He declined to discuss the results because the data have not yet been published, but he said some might respond to ginkgo's antidepressant and other effects.
Meantime, Cott, a 56-year-old consulting research pharmacologist, takes ginkgo daily: "I'm convinced by animal data, test-tube data and human data that it's good for me, and it's going to help me down the road," he said.