Tea, a beverage consumed extensively worldwide, has been reported to be associated with substantial health benefits, including a reduced risk of cardiovascular disease and type 2 diabetes. However, the mechanism underlying these benefits has been uncertain. In a new cross-sectional study, researchers from the University of Adelaide and China’s Southeast University examined the association of both the frequency and type of tea consumption with urinary glucose excretion and insulin sensitivity, as well as glycemic status, in a Chinese community-dwelling adult population. They found that compared with never tea drinkers, daily consumers of dark tea had 53% lower risk for prediabetes and 47% reduced risk for type 2 diabetes.
Tea is a popular beverage made from the leaves of the plant Camellia sinensis.
Amongst the six major tea categories in China, dark tea is the only one that involves microbial fermentation in the manufacturing process.
The popular dark teas include ripen Pu-erh tea, Liubao tea, Fuzhuan brick tea, Qingzhuan brick tea and Kangzhuan brick tea, which are respectively from Yunnan, Guangxi, Hunan or Shaanxi, Hubei, and Sichuan in China.
The fermentation of dark tea, which is also known as fermented or post-fermented tea, is different from that of black tea (full-fermented tea) and oolong tea (semi-fermented tea).
The so-called fermentation in black tea and oolong tea refers to the catalysis by endogenous enzymes — such as polyphenol oxidases and peroxidases — when the tea leaves are crashed.
However, the activity of these endogenous oxidases is passivated by heat before microbial fermentation of dark tea. It is the microbial enzymes and metabolites that play essential role in the formation of unique flavors and functions in dark tea.
The microbial fermentation also yields unique bioactive compounds (including alkaloids, free amino acids, polyphenols, polysaccharides, and their derivatives) that have potent antioxidant and anti-inflammatory…
Read the full article here