Black Tea’s Protective Power

pic 2Dementia: A Worldwide Problem that Isn’t Going Away

Nearly a year ago, the World Health Organization (WHO) held its first global conference on dementia, calling that syndrome a public health priority. According to WHO, 47.5 million people have dementia—a total that grows by 7.7 million every year!

Benefits of Green Tea

In my last post, I looked at a study that found that Japanese elderly people who drank more green tea had better cognitive activity, greater motor function, and more social engagement than non-tea drinkers. In other words, the more green tea they drank, the lower their level of functional disability.

Another Study—and How Much Is in Your Cup?

Another study that was published a few months ago focused on elderly Chinese (over 9,000 people, at least 60 years old). In this one, they considered a “cup” of tea as 250 ml or 8.45 ounces, which is considerably more than that in the study of Japanese elderly, in which a “cup” was only 100 ml or 3.38 ounces.

Study in Japan:
less than 1 cup/day = less than 3.38 ounces/day
1–2 cups/day = 3.38–6.76 ounces/day
3–4 cups/day = 10.14–13.52 ounces/day
5 or more cups/day = 16.9 or more ounces/day

Study in China:
less than 2 cups/day = less than 16.9 ounces/day
2–4 cups/day = 16.9–33.8 ounces/day
4 or more cups/day = 33.8 or more ounces/day

So people didn’t need to drink a huge amount of green tea in the Japan study to realize benefits—a “cup” in the U.S. means 8 ounces, so this is only 2 cups per day!

Black Tea: More Beneficial than Green?

engl westm_sm
English Westminster black tea

The study in China found that when at least 16.9 ounces of tea were consumed per day, the levels of depression and cognitive impairment decreased and the levels of daily living activity increased, which is consistent with the study in Japan.

Breaking down tea consumption between green and black tea (and adjusting for variables), the researchers found that drinking either green or black tea resulted in less cognitive impairment. However, “black tea consumption was significantly associated with a lower prevalence of cognitive impairment,” regardless of the tea’s strength—good news for those who prefer black tea.

Still . . .

Scientists are typically cautious about overstating their research, listing the limitations of their studies or hedging their interpretations of data with other possibilities. The authors here cite additional research studies—some of which have shown that black tea has an effect on cognitive impairment and decline whereas green tea affects only impairment, and others that have shown that green tea has a greater impact on cognitive function than does black tea.

Everyone agrees that more research needs to be done—to determine what specific components of tea (whether green or black) are producing these positive effects, and how to maximize the effects so that they can truly impact cognition and functional disability. Polyphenols and catechins seem to be top contenders, and I’ll take a look at them in future posts.

MEANWHILE: Drink Tea!!


Sources:
–”Dementia,” Fact Sheet No. 362, World Health Organization, March 2015. http://www.who.int/mediacentre/factsheets/fs362/en/
–”Tea Consumption and Cognitive Impairment: A Cross-Sectional Study among Chinese Elderly,” by Wei Shen et al. PLoS ONE 10(9):e0137781. 2015.

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