October 8, 2005
Green tea, the popular beverage drunk by millions in Asia and, increasingly, by many in the U.S. as well, may have benefits against Alzheimer's disease, researchers report. The beverage contains a compound called EGCG that appears to reduce the formation of beta-amyloid, a toxic protein that builds up in the brains of those with Alzheimer's disease. Although the studies were carried out in mice and may not apply to humans, scientists are motivated to continue research into the possible benefits of green tea for people suffering from memory loss and dementia.
The researchers, from the University of South Florida, gave high doses of the green tea compound EGCG (for epigallocatechin-gallate) to mice that had been genetically altered to produce beta-amyloid. After several months of daily EGCG injections, brain cells in treated mice contained 54 percent less beta-amyloid. The buildup of beta-amyloid is a hallmark of Alzheimer's disease, resulting in the death of healthy cells vital for memory and the formation of abnormal structures called plaquesin the brain. Many researchers believe that by blocking formation of beta-amyloid, memory loss and other troubling symptoms may be slowed or halted.
"The findings suggest that a concentrated component of green tea can decrease brain beta-amyloid plaque formation," says researcher Jun Tan, M.D., Ph.D., director of the Neuroimmunology Laboratory at the University of South Florida. "If beta-amyloid pathology in this Alzheimer's mouse model is representative of Alzheimer's disease pathology in humans, EGCG dietary supplementation may be effective in preventing and treating the disease."
Sipping Tea Not Enough
Green tea contains many different compounds called flavonoids that have powerful antioxidant activities. Antioxidants act to mop up free radicals, natural oxygen compounds that, in excess, can damage cells. EGCG is the main antioxidant in green tea. It is thought to have benefits for heart and blood vessel health, and scientists are studying it for its possible benefits in protecting against cancer as well.
But drinking green tea or taking green tea supplements rich in antioxidants may not be enough to cut Alzheimer's risk. The researchers showed that other flavonoids in green tea actually block EGCG's ability to prevent the harmful buildup of beta-amyloid. "This finding suggests that a green tea extract selectively concentrating EGCG would be needed to override the counteractive effect of other flavonoids found in green tea," says Doug Shytle, Ph.D., of the University of South Florida. In addition, the scientists note that further research is needed to determine whether EGCG actually reduces memory loss and reduces plaque formation in mice. The next step would be to test EGCG extracts in people.
In the meantime, taking a tea break won't hurt and may help. Earlier research suggests that green tea as well as other types of tea may have benefits for brain health. At the least, a cup of tea can provide a pleasant stress-reducing break during the day.
Rezai-Zadeh K, et al: "Green Tea Epigallocatechin-3-Gallate (EGCG) Modulates Amyloid Precursor Protein." Journal of Neuroscience, Volume 25. September 21, 2005, pages 8807-8814.