Anti-diabetic Activity of Antioxidative Teas and Tea Polyphenol Supplements

Abstract

Diabetes, especially type 2 diabetes (T2D) mellitus, has become one of the typical chronic diseases around the world. As the most consumed beverage, tea and its main compounds, that is, tea polyphenols, have shown various regulation effects on diabetes progression. The benefits of tea and tea polyphenols on diabetes have been verified by enzyme models, cell bioassays, and animal experiments. The mechanism may be attributed to glucose hydrolysis, glucose transport, glycogen synthesis, energy expenditure, immunity regulation, and anti-inflammatory and antioxidant capacity, among others. Furthermore, population-based investigations have mostly confirmed the effects of tea on reducing diabetes risk in many epidemiological studies. However, the intervention results of tea and tea polyphenols are not consistent. The main antioxidant mechanisms of tea and tea polyphenols may involve improvement of antioxidant enzymes, inhibition of lipid peroxidation, scavenging of free radicals, and complexation of metal ions. Tea and its bioactive components offer prevention and treatment of T2D through several mechanisms, including protecting pancreatic β-cells, improving insulin resistance, inhibiting the digestion, absorption and metabolism of carbohydrates as well as regulating the gut microbiota. In addition, they also benefit diabetic complications, such as diabetic nephropathy and diabetic cardiopathy. This chapter discusses the evidence associated with the anti-diabetic activities of tea and its reactive components, as well as the underlying mechanisms that have been studied by researchers over recent years.