Effect of cocoa and green tea consumption on glucoregulatory biomarkers in insulin resistant men and women

Abstract

In vivo and in vitro research has shown that tea and cocoa consumption may have an impact on the glucoregulatory system. While the specific mechanism of action of tea and cocoa on glucoregulatory biomarkers is uncertain, there has been speculation that dietary polyphenols may have an effect. This pilot study investigated if there was a dose-response effect of cocoa procyanidins (CP) on glucoregulatory biomarkers and compared the effect of cocoa and tea polyphenols on these outcomes. As part of a randomized crossover design, 20 subjects (10 men, 10 women) each consumed a controlled diet at weight maintenance along with 5 treatment beverages: high dose cocoa (900 mg CP), medium dose cocoa (400 mg CP), low dose cocoa (200 mg CP) control cocoa (22 mg CP), and green tea. Each subject consumed the treatments with breakfast and the evening meal for 5 days. On the sixth day subjects underwent an oral glucose tolerance test (OGTT). Biomarkers measured were glucose, insulin, insulin sensitivity index (ISI), and homeostasis model assessment of insulin resistance (HOMA-IR). The OGTT confirmed that 12, 7, and 1 subjects were insulin resistant (IR), normal, and diabetic, respectively. Results showed no significant changes in glucose and insulin after consumption of the cocoa treatments. Green tea compared to cocoa lowered glucose (p=0.0003) and elicited a lower insulin response (p=0.0157) in normal subjects but not in IR subjects. Cocoa and green tea did not affect ISI or HOMA-IR. Consumption of cocoa and green tea had no effect on glucoregulatory biomarkers in IR men and women.