Green Tea Compounds Show Dementia Benefit
Lee Swanson Research Update
The in vitro study, published in Phytomedicine, confirmed that in post-digestion, extracts of the phytochemical-rich drink show protective effects for dementia.
The researchers investigated whether the protective properties of green tea—which have previously been shown to be present in the undigested, freshly brewed form of the drink—were still "active" once the drink had been digested.
Lead researcher Dr. Ed Okello from Newcastle University, U.K. said that just because a consumed food is generally accepted to contain health-boosting properties, it should not be assumed that such compounds will ever be absorbed in the body.
"What was really exciting about this study was that we found when green tea is digested by enzymes in the gut, the resulting chemicals are actually more effective against key triggers of Alzheimer’s development than the undigested form of the tea," explained Okello.
Alzheimer’s disease—the most common form of dementia—is a progressive and irreversible neurodegenerative disorder associated with cognitive dysfunction.
The authors noted that "mounting evidence" suggests that beta-amyloid peptides in conjunction with free radical species (such as hydrogen peroxide) in the brain play a significant role in the development and pathogenesis of Alzheimer’s.
Green tea is high in flavan-3-ols, which are believed to be efficient scavengers of highly reactive free radical species, and have been shown to exhibit hypocholesterolemic and neuroprotective properties in previous research.
Okello said that although research has identified certain compounds as beneficial for health, and in many cases has identified foods with high concentrations of such compounds, he explained that "what happens during the digestion process is crucial to whether these foods are actually doing us any good."
"Flavan-3-ols have been reported to possess properties beneficial to health, [but] they are known to undergo significant metabolism and conjugation in the gastrointestinal tract," said the researchers.
"It is unknown how such metabolism and conjugation may influence the putative properties of these polyphenols, hence the focus of our study on a digested green tea extract," they explained.
Phytomedicine Published online ahead of print.
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Jan., 2011