Scientists are beginning to look into just how tea might affect mood and cognition. Specifically, they’re investigating whether it’s relaxing and alerting effects are a direct biological outcome of the compounds in tea or whether they come from the context in which the drink is consumed — preparing your brew, choosing your favorite cup and sitting down for a brief respite from the world. Or both.
Green and black tea come from the same plant — Camellia sinensis. Green tea, however, is processed in a different way, which results in higher levels of some of the compounds that scientists believe have positive effects on our mental health.
Drinking green tea has been found to improve brain function in healthy people, said Stefan Borgwardt, chair and director of the department of psychiatry and psychotherapy at the University of Lübeck, Germany.
In a 2014 study, he gave green tea extracts equivalent to one or two cups of green tea to 12 healthy volunteers and imaged their brains to analyzechanges in connectivity inside certain brain regions.
“We noticed an increased connectivity in regions of the brain associated with working memory,” he said via email.
And a 2017 review of more than 100 studies he coauthored found that green tea can impact the brain in three ways: It can influence psychopathological symptoms such as reducing anxiety; cognition by benefiting memory and attention; and brain function, specifically memory.
That review concluded that “it would be desirable” for more Westerners to consume at least 100 milliliters (3.3 fluid ounces) of green tea each day “to protect neurocognitive function.”
However, Borgwardt cautioned that the effects aren’t large, and current evidence is mainly provided by small-scale studies.
What’s less clear is which compounds found in tea are responsible for various improvements in our brain power and whether they work alone or together.
The most important are antioxidants such as epigallocatechin gallate (EGCG), the most abundant, followed byL-theanine, an amino acid found in tea leaves, and caffeine.
Tea also has some benefits for our physical health — it’s linked to a longer life, lower blood pressure and may also have a fat-busting effect.
Gunter Kuhnle, an associate professor at the department of food and nutritional science at the University of Reading in the UK, researches the benefits of flavanols, which are found in tea, cocoa and some fruits.
He said one of the problems of assessing the benefits of tea and its beneficial compounds is that studies reporting effects are usually observational, reliant on subjective self-reporting and the impact of how food is prepared and consumed.