When tea leaves are allowed to fully ferment, they develop the bold, tannic, earthy flavor of black tea. (Its color, though, is closer to red.)
Four antioxidant compounds (called theaflavins) found in black tea appear to protect the brain from disease in a very specific way. Last year a group of German researchers published findings stating that these compounds prevented the formation of senile plaques (likely by binding to amino acids that would have otherwise formed the plaques), which contribute to the development and progression of Alzheimer's and Parkinson's.
Derived from the leaves of a holly species native to South America, yerba maté has a strongly herbal, almost grassy flavor. For a less bitter taste, steep in hot (not boiled) water.
In a 2011 study, scientists added yerba maté to petri dishes containing colon cancer cells. "Put simply, the cancer cells self-destructed," says study author Elvira Gonzalez de Mejia, PhD. "Caffeine-related compounds in the tea damaged their DNA." More research is needed, but Mejia is optimistic that yerba maté could help the body fend off colon cancer.
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