The Effects of Acute Consumption and Chronic Supplementation of Cocoa on Overweight and Obese Adults at Risk of Developing Diabetes

The prevalence of obesity and diabetes is increasing in the United States and abroad and strategies are needed to prevent the progression from an at-risk state to the clinically diagnosed diseases. Flavanols in cocoa powder have been shown to reduce blood glucose concentrations, improve insulin sensitivity, and decrease gut permeability in animals and humans, but it is unknown if this occurs in adults with prediabetes. Therefore, we first hypothesized that an acute dose of cocoa would reduce postprandial glucose and enhance insulin and incretin hormone responses to a mixed meal challenge compared to a placebo. Second, we hypothesized that 15 g cocoa/day for 4-weeks would reduce gut permeability, attenuate endotoxin response to a high fat meal, improve insulin sensitivity, and improve measures of skeletal muscle substrate flexibility in a randomized, double blinded, placebo controlled parallel group design. To test the first hypothesis, 30 overweight or obese volunteers who were at-risk for diabetes completed two meal challenges using a randomized crossover design. Blood samples were collected hourly for 4 hours and were analyzed for glucose, insulin, C-peptide, glucagon-like peptide 1 (GLP-1), and gastric inhibitory peptide (GIP). Cocoa did not influence these measures. However, participants with the lowest fasting blood glucose concentrations were more likely to respond to the cocoa as hypothesized. To test our second hypothesis, 15 overweight or obese adults at risk for developing diabetes consumed either the cocoa or placebo treatments along with a controlled diet for one month. Overall, cocoa did not seem to influence insulin sensitivity, gut permeability, or endotoxin levels, although cocoa may influence skeletal muscle substrate metabolism. In conclusion, the data for both studies suggests that cocoa did not exert substantial effects on the evaluated outcomes. However, the experiments did provide valuable information about incretin hormone levels in adults with impaired glucose tolerance. More research is needed to understand how cocoa can affect glucose homeostasis for overweight or obese adults.