A review of 34 randomized, controlled trials published in the February 2021 issue of Clinical Nutrition ESPEN (European Society for Clinical Nutrition and Metabolism) concluded that regular intake of green tea and its active components may help improve endothelial function and reduce the risk of cardiovascular disease.

Endothelial function describes the ability of the inner lining of the blood vessels to effectively perform its roles, which include blood pressure regulation. Endothelial dysfunction has been implicated as a leading cause of atherosclerosis.

A team of researchers from Africa and Italy selected 14 trials that reported the effect of tea intake on endothelial function among healthy men and women, five trials that examined tea’s effects among smokers, eight trials that included coronary artery disease patients and seven trials involving participants with metabolic syndrome. Tea use was defined as regular intake of green, oolong or black tea, or capsules that contained powdered tea solids or extracts rich in tea compounds, such as EGCG.

Among the effects uncovered by the trials, regular tea consumption was associated with lower blood pressure and enhanced bioavailability of nitric oxide (a gas produced in the body that helps relax the arteries), which indicates a beneficial effect for tea on endothelial function. In some studies, tea was associated with lower markers of oxidative stress (oxidized low-density lipoprotein) and inflammation (C-reactive protein), both of which also suggest improved endothelial function. An increase in flow mediated dilation (a measure of endothelial function) was observed in studies that assessed the effects of consuming black tea.

Overwhelming evidence summarized in this review supports the beneficial effects of tea in improving endothelial function in individuals with or without coronary artery disease, the authors wrote. They concluded that the findings suggest that the development of epigallocatechin gallate as a nutraceutical or enriching foods with this bioactive compound could be a feasible strategy to improve endothelial function and lower cardiovascular disease risk.

In another investigation, published on January 23, 2021 in Complementary Therapies in Clinical Practice, men and women with diabetic peripheral neuropathy experienced improvement in several factors related to the condition when given capsules that contained green tea extract. Peripheral neuropathy can occur when chronically elevated blood glucose damages the nerves, causing numbness and pain.

One hundred ninety-four participants with mild to moderate diabetic peripheral neuropathy received capsules that contained 500 milligrams green tea extract or a placebo three times per day for 16 weeks. Pain and nerve dysfunction were evaluated at the beginning of the study and at four, eight and 16 weeks. Although differences between the groups were seen at eight weeks, it was evident at the end of the study that green tea extract was associated with significant improvement in comparison with the placebo.

To the best of our knowledge, this is the first study to investigate the role of green tea extract in this population, Ahmed Essmat and Mohammed Salah Hussein of Al-Ashar University wrote. Green tea extract intake may have a beneficial value in treatment of diabetic peripheral neuropathy.

Studies such as these continue to build on the positive effects found for tea in the maintenance of good health and support its role in a healthy eating and supplementation program.