Effect of oolong tea, oolong tea polyphenols and oolong tea catechins on glucoregulatory control in overweight and obese men

Abstract

Oolong tea, as well as the polyphenols it contains, has been shown to alter physiological processes related to glucose regulation. As part of a double blinded randomized crossover design study, 19 overweight and obese men (BMI 25‐34, ages 25‐64 years) consumed a controlled diet at weight maintenance along with 5 treatment beverages: 1) oolong tea, 2) oolong tea with added catechins, 3) oolong tea with added oolong tea polyphenols, 4) water with caffeine (matched for caffeine content of oolong tea) and 5) water. Each subject consumed four 350 ml servings (1400 ml/day) of the treatment beverages per day with breakfast, lunch, mid‐afternoon and dinner for four days. On the fifth day, after a 12 hour fast, subjects consumed a mixed meal tolerance test breakfast (450 kcals, 85 g carbohydrate, 10 g fat, 8 g protein) along with the treatment beverage. Biomarkers, glucose, insulin, triglycerides and the homeostasis model assessment of insulin resistance (HOMA‐IR), were measured every 30 minutes during a four hour period. Results showed no significant postprandial changes in glucose, insulin, triglycerides and HOMA‐IR after consumption of the treatment beverages. Consumption of the oolong tea treatments had no adverse effects on glucoregulatory biomarkers in overweight and obese men.Supported by US Department of Agriculture and Suntory Corporation, Osaka, Japan