A recent study published in Nutrients shows that theaflavins—found in black tea—may improve vascular function in healthy people.

Theaflavins are unique to black tea, and are formed from catechins during the enzymatic oxidation of tea leaves. The study was performed to gain more insight into the effects of theaflavins on microcirculation and to compare effects with another flavonoid class—catechins, which are derived from green tea and have been reported to improve vascular function.

Twenty-four health adults were recruited for the double-blind, placebo-controlled, randomized, cross-over study. On six different days, subjects received capsules with a single dose of catechins (500 mg), four varying doses of theaflavins (100 to 500 mg), or a placebo. Microcirculation was assessed after each treatment by Pulse Amplitude Tonometry (EndoPAT) at baseline and two, four and six hours after test product intake.

Results showed the 500 mg dose of theaflavins and catechins both improved microcirculation measures when compared to the placebo. In addition, improvements in microcirculation were shown with the 300 mg dose of theaflavins, but no effects were observed at lower doses.

The researchers concluded that “catechins and theaflavins may contribute to the vascular effects of green and black tea, respectively. The moderate effects suggest that other components in tea may also play a role in affecting vascular function. Therefore, more research is required to explain why green tea and black tea show similar sized effects on vascular function despite the differences in composition."