Polyphenol constituents and impacts of fermented teas (Camellia sinensis) in human wellness

The latest insights into the health benefits of various fermented teas, including dark tea, oolong tea, and black tea, underscore the significant role of polyphenols in promoting wellness. The fermentation process in these teas not only enriches their overall polyphenol content but also enhances level of specific polyphenols, improving their health-promoting effects. Dark tea, such as Pu-erh, undergoes microbial fermentation, resulting in unique polyphenol profiles particularly theabrownins that offer potent antioxidant properties. Oolong tea, which is partially oxidized contains catechins and theasinensins, contributing to its potential to enhance weight management and correct metabolic disorders. Black tea, a fully oxidized tea, has a high levels of theaflavins and thearubigins, polyphenols linked to reduced inflammation, decreased incidences of cancer, and enhanced neuroprotection. However, despite these benefits, the emerging understanding of the health risks has associated fermented teas with the presence of potentially harmful compounds formed during fermentation or processing. In dark tea, prolonged microbial fermentation may lead to the production of mycotoxins, such as aflatoxins, which have been linked to carcinogenic effects. Black tea may accumulate heavy metals from soil and processing, posing risks to human health if consumed in excessive amounts. Similarly, oolong tea, while partially fermented, can still contain heavy metals contributing to impaired health. While these risks are generally low and depend on factors such as brewing conditions and consumption frequency, they highlight the importance of conducting future studies to devise preventive measures to mitigate these risks.