Green Tea Linked to Maintaining Cognitive Function

One of the first studies to investigate the link between green tea and brain health in humans has found that green tea consumption is linked to a reduced prevalence of cognitive impairment.

Past cell culture and animal studies have found that green tea may protect the brain against degenerative processes leading to Alzheimer’s and Parkinson’s and that it can inhibit the buildup of amyloid proteins associated with Alzheimer’s. However, until now, human studies have not been done.

In the current study, researchers analyzed data from 1,003 Japanese subjects who had participated in a community-based Comprehensive Geriatric Assessment conducted in 2002. The subjects, aged 70 or older, completed a self-administered questionnaire that included questions about their diets, overall physical health, lifestyle habits and frequency of green tea consumption. Researchers evaluated cognitive function by using the Mini-Mental State Examination, which measures memory, attention and language use.

The results indicated that higher green tea consumption was associated with a lower prevalence of cognitive impairment. Subjects who consumed two or more cups of green tea per day had about half the chance of developing cognitive impairment compared to those who drank three cups or less each week. Participants who drank about one cup per day also reduced their risk of mental decline by 40%, although not by as much as those consuming two or more cups per day, demonstrating a 54% decreased risk of mental decline.

Black and oolong tea drinkers exhibited a slight decrease in mental decline. Coffee had no effect on cognitive decline.

Researchers concluded: "A higher consumption of green tea is associated with a lower prevalence of cognitive impairment in humans." The researchers suggested that green tea’s potential ability to support brain health may help explain the lower rate of Alzheimer’s disease in Japan compared with Europe and North America.

Summary: Over 1000 Japanese subjects participated in a study in 2002. The subjects, ages 70 and older, were questioned about their diets, overall health, lifestyle habits and frequency of green tea consumption. All subjects underwent cognitive testing to measure memory, attention and use of language.

It was found that those with higher green tea consumption had a decreased prevalence of cognitive impairment. For example, subjects who consumed two or more cups of green tea a day had about half the chance of developing some cognitive impairment compared to those who drank three cups or less per week. The effects of green tea on cognitive functioning remained even after researchers adjusted for overall diet, smoking and exercise habits. Study authors suggested that green tea's potential ability to support brain health may explain the lower rates of Alzheimer's disease in Japan compared to Europe and North America.

Background: Although considerable experimental and animal evidence shows that green tea may possess potent activities of neuroprotection, neurorescue, and amyloid precursor protein processing that may lead to cognitive enhancement, no human data are available.
Objective: The objective was to examine the association between green tea consumption and cognitive function in humans.

Design: We analyzed cross-sectional data from a community-based Comprehensive Geriatric Assessment (CGA) conducted in 2002. The subjects were 1003 Japanese subjects aged 70 y. They completed a self-administered questionnaire that included questions about the frequency of green tea consumption. We evaluated cognitive function by using the Mini-Mental State Examination with cutoffs of <28, <26, and <24 and calculated multivariate-adjusted odds ratios (ORs) of cognitive impairment.

Results: Higher consumption of green tea was associated with a lower prevalence of cognitive impairment. At the <26 cutoff, after adjustment for potential confounders, the ORs for the cognitive impairment associated with different frequencies of green tea consumption were 1.00 (reference) for 3 cups/wk, 0.62 (95% CI: 0.33, 1.19) for 4–6 cups/wk or 1 cup/d, and 0.46 (95% CI: 0.30, 0.72) for 2 cups/d (P for trend = 0.0006). Corresponding ORs were 1.00 (reference), 0.60 (95% CI: 0.35, 1.02), and 0.87 (95% CI: 0.55, 1.38) (P for trend = 0.33) for black or oolong tea and 1.00 (reference), 1.16 (95% CI: 0.78, 1.73), and 1.03 (95% CI: 0.59, 1.80) (P for trend = 0.70) for coffee. The results were essentially the same at cutoffs of <28 and <24.

Conclusion: A higher consumption of green tea is associated with a lower prevalence of cognitive impairment in humans.

Source:

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 1. Am J Clin Nutr. 2006 Feb;83(2):355-61.

Key concepts: green tea, cognitive function