Aside from water, tea is the most commonly consumed beverage in the world.¹ In the US, black tea is by far the most popular, but green tea (which accounted for just 15 percent of the tea consumed in America in 2014²) may have particularly powerful health benefits.

Regardless of variety, black and green tea (as well as oolong, dark, and white teas) come from the same plant, an evergreen called Camellia sinensis. It is the processing method and degree of oxidization (exposure to oxygen) that creates the different tea types.

While black tea is oxidized, green tea is not oxidized at all after the leaves are harvested. This minimal oxidation may help to keep the beneficial antioxidants in green tea intact. As explained by the World of Tea:³

 “Controlled oxidation usually begins after tea leaves are rolled or macerated, two processes that break down the cell walls in tea leaves. Chemically speaking, oxidation occurs when the polyphenols in the cell’s vacuoles and the peroxidase in the cell’s peroxisomes come in contact with the polyphenol oxidase in the cell’s cytoplasm.

The resulting reaction converts tea catechins into theaflavins and thearubigins. Theaflavins provide tea with its briskness and bright taste as well as its yellow color, and thearubigins provide tea with depth and body and its orange-brown color.

This conversion of catechins to theaflavins and thearubigins means that the longer the oxidation, the lower the amount of catechins in the finished tea. Also, during oxidation chlorophylls are converted to pheophytin, a pigment that lends to the dark color of oxidized teas. Lipids, amino acids, and carotenoids also degrade during oxidation to produce some of tea’s flavor and aroma volatile compounds.”

Drinking Green Tea Every Week May Slow Mental Decline

Green tea shows promise for protecting brain health. In a study presented at the 2015 International Conference on Alzheimer’s and Parkinson’s Diseases, those who drank green tea one to six days a week had less mental decline than those who didn’t drink it.⁴

In addition, the researchers revealed that tea drinkers had a lower risk of dementia than non-tea drinkers. It’s not the first time green tea has been linked to brain health. In a study of 12 healthy volunteers, those who received a beverage containing 27.5 grams of green tea extract showed increased connectivity between the parietal and frontal cortex of the brain compared to those who drank a non-green tea beverage.⁵

The increased activity was correlated with improved performance on working memory tasks, and the researchers believe the results suggest green tea may be useful for treating cognitive impairments, including dementia. According to the study authors:⁶

“Our findings provide first evidence for the putative beneficial effect of green tea on cognitive functioning, in particular, on working memory processing at the neural system level by suggesting changes in short-term plasticity of parieto-frontal brain connections.

Modeling effective connectivity among frontal and parietal brain regions during working memory processing might help to assess the efficacy of green tea for the treatment of cognitive impairments in psychiatric disorders such as dementia.”