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Green tea protects the brain

Few dietary substances have been examined more extensively than green tea, mainly because study results continue to show broad spectrum positive effects. In addition to favorable effects on obesity, heart disease and diabetes, a growing number of studies over the last decade strongly indicate that the major component of green tea, epigallocatechin-3-gallate (EGCG), improves brain health. Here’s a quick look at what we know about the impact of green tea consumption on cognitive function.

62% less chance of cognitive impairment for those drinking a cup a day of green tea

Epidemiological studies consistently show that higher consumption of tea, especially green tea, is associated with better brain health. In a large study of over 1,000 elderly Japanese subjects greater than 70 years of age, the prevalence of cognitive impairment decreased with increasing consumption of green tea across a range of intakes.For example, individuals who consumed 4-6 cups of green tea per week had a 62% less chance of having cognitive impairment.

In another study of 716 Chinese adults, total tea consumption was positively associated with an array of brain functioning measures including global cognition, memory, executive function, and information processing speed.2

Epidemiological studies are limited by the many confounding factors that can impact brain health. Seemingly strong associations can often be proven false through more rigorously controlled clinical studies. Thus, it is important to look at mechanistic studies in animal and humans, and clinical intervention studies that have evaluated the ability of green tea to improve brain health.

Spatial learning and memory effect of green tea in animal studies

In two animal studies, long-term feeding of green tea in rats resulted in improved ability to navigate a swim maze compared to age-matched control animals. Rats given green tea also had significantly less free radicals and greater antioxidant capacity. 3,4  These studies indicate green tea can affect behavior, in particular spatial learning and memory. Other animal studies provide consistent evidence for a positive role of EGCG in protecting from Parkinson’s and Alzheimer’s disease. 5,6,7,8

Human studies show positive changes in brain electrical activity

In the last few years, human intervention data is beginning to corroborate the epidemiological and animal data supporting a favorable effect of green tea on brain health. In a double-blind, placebo-controlled cross-over study, healthy young subjects were given a single dose of either 300 mg EGCG or a placebo.9  Electrical activity from electrodes placed on the top of the head and a series of mood tests were performed before and 120 minutes after ingestion of EGCG and placebo. EGCG was associated with higher self-rated calmness and decreased stress, which was consistent with the brain electrical activity patterns that reflected greater calmness and relaxation.

Studies by Swiss and German researchers using a more sophisticated functional magnetic resonance imaging (fMRI) neuroimaging technique to assess brain activity indicate that green tea favorably modulates specific brain activity patterns. They had healthy young subjects perform a working memory task after consuming a whey-based drink with and without green tea.

The drink with green tea resulted in increased activity in the dorsolateral prefrontal cortex, a key region of the brain that mediates working memory processing.10  In a follow-up study, they showed additional effects of green tea from their fMRI data indicating a beneficial effect on connectivity between important regions of the brain involved in memory, and these patterns were associated with improved performance on a memory task.11

What’s an effective dose of EGCG? 

Precise dosing guidelines are not available and depend on the person and the effect desired, but effective amounts of EGCG in green tea are likely achieved with 200-300 mg per day.

What if you don’t like drinking green tea?

Is there another way to get the benefit? If you drink green tea, there can be a great deal of variability in the content of bioactive compounds including EGCG depending on how the tea leaves were processed prior to drying, the geographic location and growing conditions, the tea type (decaffeinated, instant, etc.), and preparation method (amount used, brew time, temperature). Because of these “unknowns”, supplements that contain standardized extracts of EGCG are a good option.

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