Tea consumption began in China around 2737 B.C. and has since become a staple among Asian and English cultures. The use of tea for medicinal purposes have prevailed for centuries in traditional Chinese medicine, but only recently gained prominence in the modern “alternative medicine” community. There has been increased interest and active biomedical research on tea extracts, with dozens of peer-reviewed scientific articles published each month exploring the health properties of green tea. Through in vitro and animal studies, green tea (derived from the Camellia sinensis plant) and its polyphenol compounds — in particular, epigallocatechin-3-gallate (EGCG) — have been associated with possible risk reductions in some cardiovascular, neurologic, and oncologic disorders. Human trials are however sparse or equivocal.
I previously reported on a Japanese study correlating green tea consumption with a lower prevalence of cognitive dysfunction. A similar research group from the Tohoku University School of Medicine (Sendai, Japan) has continued to analyze the benefits of green tea with other health outcomes: causes of mortality, cardiovascular disease, pneumonia, and cancers. Their most recent study, published in the American Journal of Epidemiology, evaluated the influence of green tea consumption on the development of hematologic malignancies.
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Alzheimer disease is a chronic condition that afflicts more than 14% of the geriatric population. It is the most common cause of dementia, characterized by a progressive decline in cognitive function. Although there are pharmaceutical drugs (i.e., donepezil) that attempt to stave this decline, there is yet no cure.
A recent study published in the American Journal of Clinical Nutrition has correlated green tea consumption with a lower prevalence of cognitive impairment. Although previous animal studies have suggested a protective effect of green tea against neurodegenerative diseases, this is the first study that addresses the topic in humans.
Researchers at the Tohoku University School of Medicine (Sendai, Japan) surveyed 1003 geriatric citizens at ages 70 years or older from the Tsurugaya district of Sendai City. The study examined several variables, including the consumption of certain beverages, the health status, and the social habits of the participants. Their cognitive function was assessed using the Mini-Mental Status Examination (MMSE), a tool commonly used by neurologists and geriatricians.
The study found that participants who routinely consumed greater quantities of green tea generally scored higher on the MMSE. Consumption of black or oolong tea, or coffee did not produce similar trends. The researchers also adjusted the data for several possible confounders, such as presence of different diseases, level of physical activity, educational background, dietary habits, and substance use. The results still demonstrated a positive effect of green tea in cognitive function.
Does green tea hold promise for dementia patients? Can it reverse the cognitive decline in Alzheimer disease? What about using it as prophylaxis by healthy individuals? The findings are exciting, but there is yet much research needed to validate and extend the results of the Tsurugaya Project.
- Kuriyama S, Hozawa A, Ohmori K, Shimazu T, Matsui T, Ebihara S, Awata S, Nagatomi R, Arai H, Tsuji I. Green tea consumption and cognitive function: a cross-sectional study from the Tsurugaya Project. Am J Clin Nutr 2006;83:355-61.
