Regular readers of this column know that I have a strong interest in lifestyle- and diet-based approaches to disease prevention, but that I insist on rigorous, high-quality research-based data before I can recommend a particular lifestyle or dietary modification to my readers (or to myself). Many past columns have reviewed the findings of research studies with favorable results associated with specific nutritional or other lifestyle approaches to disease prevention. However, this week’s column will report on a newly published prospective clinical research trial that calls into question the supposed clinical value of the traditional Chinese medicine herb Ginkgo biloba in reducing the cognitive decline associated with aging and Alzheimer’s disease.

Previously published public health research data, based upon low-powered research methods, have suggested that dietary supplementation with Ginkgo biloba might be able to improve memory and cognition, particularly in older adults. However, more recent data, based upon more robust types of clinical research, have called this assumption into question (as well as previous claims that Gingko biloba can delay or reverse the cognitive decline associated with Alzheimer’s disease). Now, a newly published prospective, randomized, double-blind, placebo-controlled clinical trial of Gingko biloba supplementation in older adults in the United States appears to have definitively resolved the controversy about the value of Gingko biloba in maintaining memory, and other high level cognitive functions, in older adults.

Ginkgo biloba trees are often referred to as living fossils, as they are known to survive for 1,500 years or more, and their presence has been documented within fossil-bearing rocks more than 270 million years old. Although ancient fossils containing the distinctive bilobed leaves of Ginkgo biloba trees have been found on multiple continents, modern day Gingko trees now grow naturally only in China (although they have been widely cultivated, over a period of centuries, throughout Asia, and particularly in Japan and Korea).

A new highly-powered prospective clinical research trial evaluating Ginkgo biloba supplementation appears in this week’s issue of the Journal of the American Medical Association. More than 3,000 adults between the ages of 72 and 96 years participated in this placebo-controlled research trial, with an impressive average patient follow-up duration of more than 6 years. These patient volunteers were secretly randomized to one of two groups. The patients in the “experimental group” received 120 mg of Ginkgo biloba extract twice daily during the course of this study, while the “control group” of patients received an identical-appearing placebo (“sugar pills) twice daily. (As this was a double-blind study, neither the patient volunteers nor the researchers knew which patients were receiving Gingko pills and which were receiving the placebo pills until after the research study was completed.)

Multiple validated cognitive screening exams were given to all of these older patient volunteers during each year of the study, and the rate of annual decline in cognitive function was then compared between the two groups of patient volunteers. Areas of cognitive function that were specifically tested for in this high-powered prospective clinical research trial included memory, attention, visual-spatial abilities, language function, and overall executive brain function. (Note: these same cognitive function tests are also routinely utilized to assess cognitive function in patients with Alzheimer’s disease.) (more…)