The herbal supplement Ginkgo biloba does not help prevent dementia or Alzheimer's disease among healthy elderly people or those with mild cognitive impairment, suggests a study released Tuesday.

The randomized placebo-controlled trial of 3,069 people aged 75 or older from five U.S. cities followed participants with dementia assessments for an average of six years, to determine whether a daily dose of ginkgo could delay or prevent dementia.

Ginkgo biloba at 120 milligrams twice a day was not effective in reducing either the overall incidence rate of dementia or Alzheimer's disease incidence in elderly people with "normal cognition" or those with mild cognitive impairment, concluded Dr. Steven DeKosky, dean of the University of Virginia School of Medicine, and his colleagues.

"Based on the results of this trial, Ginkgo biloba cannot be recommended for the purpose of preventing dementia," DeKosky said.

DeKosky said he was disappointed with the results, given that the smaller trials suggested the antioxidant may help preserve memory.

"If they want to continue taking it — because it's not toxic and not expensive — they probably aren't going to hurt themselves other than spending the money," DeKosky said.

During the study, 246 people in the placebo group developed dementia and 277 in the ginkgo group did, the researchers said.

Since it takes years for early changes in the brain to progress to clinical dementia, DeKosky said he cannot rule out that ginkgo may have shown a benefit if the study had gone on longer.

This Ginkgo Evaluation of Memory or GEM trial is the largest and longest randomized controlled trial of the herbal supplement to be undertaken, and included the bulk of non-industry-funded, placebo-controlled data, Dr. Lon Schneider of the department of psychiatry and behavioural sciences and neurology at the University of Southern California, Los Angeles, noted in a journal commentary accompanying the study.

Stroke risk identified

Canadians spend more than $4 million annually on ginkgo supplements, making it one of the top five supplements sold in the country, according to Jamieson Laboratories based in Toronto.

Studying people who are middle aged rather than elderly would be the best way to analyze ginkgo's effects, said Daniel Fabricant of the Natural Products Association.

The trade group said there may still be a role for ginkgo in treating rather than preventing Alzheimer's. It's thought that ginkgo may protect the brain by preventing the buildup of an Alzheimer's-related protein or preventing oxidative damage to cells.

Statins, estrogen, anti-inflammatory drugs, vitamin E and drugs called cholinesterase inhibitors have also failed to prevent Alzheimer's, said Dr. Murali Doraiswamy, a memory expert at Duke University Medical Center in Durham, N.C.

Doraiswamy said the findings would lead him to discourage people from turning to ginkgo supplements to prevent Alzheimer's.

The study also found an infrequently occurring but serious adverse event called hemorrhagic stroke, or bleeding in the brain, said Dr. Tiffany Chow, a clinician scientist with the Baycrest Centre for Geriatric Care in Toronto.

There were eight such events in the placebo group and 16 in the ginkgo group, a difference that is not statistically significant, Schneider said. Both Schneider and Chow said elderly patients with cardiovascular disease should carefully consider the risk before taking the supplements.

Chow said current recommendations to help Alzheimer's include:

• Eating a Mediterranean diet rich in fruits and vegetables, olive oil, grains, nuts and fish.
• Exercising regularly to help the heart and brain work well.
• Reducing stress.
• Keeping in touch with other people and using your sense of humour, since social isolation is a risk factor.

German-based Schwabe Pharmaceuticals provided the ginkgo extracts used in the study and had no role in the research.

Both DeKosky and Schneider reported receiving grants or research support from several pharmaceutical companies, including manufacturers of dementia drugs.

Ginkgo is also taken for leg pain, ringing in the ears and sexual dysfunction.

With files from Reuters, Associated Press