A new study shows that consuming green tea can immediately enhance cognitive functioning, including working memory. Perhaps more excitingly, this study also offers insight into the neurological mechanisms behind this phenomenon. Though tea aficionados have long lauded the alleged health benefits of green teas, this is the first study to thoroughly examine these claims.
The traditions of consuming green tea began over 3,000 years ago in mainland China. Before it was consumed as a normal beverage, green tea was first drunk exclusively for medical purposes. Green tea is made from the mature leaves of the tea plant, Camellia sinensis. Green tea is made by steaming or pan frying fresh tea leaves, rolling them, and then drying them. Compared to black tea which is fermented for an extended period of time, green tea preparation involves minimal processing. This is why so many antioxidants and other beneficial compounds persist in greater abundance in green tea.
Chemically speaking, about 30 percent of green tea consists mainly of a particular type of polyphenol molecules called “catechins.” Catechins such as caffeine, (-)epigallocatechin gallate (EGCG), and theanine are antioxidants—meaning that they have a protective effect against cell damage.
To test the cognitive effects of green tea on working memory, researchers conducted a double-blind, counterbalanced study in which 12 healthy and verified substance-free volunteers were either given a drink containing green tea extract, or an otherwise identical placebo that lacked the extract. After consuming the drink, the research subjects participated in a series of memory tests while hooked up to a functional magnetic resonance imaging (fMRI) device.
The resulting data indicated that subjects that had consumed the green tea extract showed improved working memory function. An examination of the fMRI images indicated that the brains of the subjects that had received the experimental treatment had greater connectivity between the right parietal lobe (which is used to process sensory information) and the middle frontal gyrus (used for information interpretation).
Furthermore, it was found that some of the key catechins that make up green tea mimicked one of the body’s natural biochemical pathways: the N-methyl-D-asparate receptor (NMDAR) pathway. The NMDAR pathway is key to the brain’s ability to adapt and respond to external stimuli (a.k.a. brain plasticity) and is known to be essential for learning and memory.
However it is worth noting that the 27.5 grams of green tea extract administered to the research subjects in this study represent an extremely large intake of green tea—around six to seven cups. While drinking such a large quantity of tea may indeed produce positive effects on memory, many might find it impractical to consume that volume of liquid. In addition, for those that still need their caffeine fixes, green tea consumption is not the most effective option for caffeine intake. Six cups of green tea contains only about 150 mg of caffeine, or the equivalent of 1.5 cups of generically brewed coffee.
The results of this study confirm correlational evidence that further back the claimed health benefits of green tea. A study by the National Institute of Health found that consuming a cup of green tea a day correlated with a 46 percent reduction in blood pressure. In addition, a single cup of strong green tea is said to have half of a person’s daily requirement of vitamin C, leading many to believe that green tea has immune system-boosting qualities. Finally, experimental evidence also suggests that green tea and other flavonoid-rich foods reduce cognitive impairment in mice with Alzheimers disease. Such discoveries suggest that in the future green tea and/or green tea extract will be developed for clinical uses in enhancing memory and promoting health.
By Sarah Takushi