Green Tea Protection from Alzheimer's
Researchers at the University of South Florida (USF) have found that green tea may protect the brain against Alzheimer's disease (AD). In the study, published in the September 21 issue of the Journal of Neuroscience, it was found that a component of green tea, epigallocatechin-3-gallate (EGCG), prevented AD-like damage in the brains of mice genetically programmed to develop the disease. After treating amyloid precursor protein (APP)-overexpressing mice for several months with daily injections of pure EGCG, the researchers observed a dramatic decrease (as much as 54%) of AD plaques; this reduction in amyloid beta (Abeta) was also observed in murine neuron-like cells (N2a) transfected with the human "Swedish" mutant APP.
EGCG, which is the main polyphenolic constituent of green tea and has been widely studied for its reported protection against certain cancers, appeared to block the initial process by which the protein is formed in brain cells. Recent studies have suggested that green tea flavonoids may be used for the prevention and treatment of a variety of neurodegenerative diseases. These findings suggest that a concentrated component of green tea can decrease brain Abeta plaque formation. According to senior study author Dr. Jun Tan, if Abeta pathology in this AD mouse model is representative of the disease's pathology in humans, EGCG dietary supplementation may be effective in preventing and treating AD. However, Tan's team demonstrated that other flavonoids in green tea actually oppose naturally occurring EGCG's ability to prevent the harmful build-up of Abeta.
Thus, drinking green tea would not likely have a beneficial effect through the same mechanism that EGCG works. Instead, a green tea extract selectively concentrating EGCG would be needed to override the counteractive effect of other flavonoids found in the tea. It is thought that humans would likely need 1,500mg to 1,600mg of EGCG daily to approximate the injection dosage that benefited the AD mice; this dosage has already been studied in healthy human volunteers and was found to be safe and well tolerated. The USF researchers plan to study whether multiple oral doses of EGCG can improve memory loss in AD mice, as well as reducing their AD plaque burden. If these studies show clear cognitive benefits, the team believes that clinical trials of EGCG to treat AD would be warranted.
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