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. / Ph. D. / The purpose of this research project was to determine if cocoa powder could influence how we digest food and improve our health. For many people in the United States and abroad, controlling blood sugar levels is important for their well-being; uncontrolled spikes in blood sugar levels can eventually lead to type 2 diabetes and heart disease. Our first hypothesis was that one serving of cocoa could help reduce large spikes in blood sugar after a meal. Secondly, we hypothesized that consuming cocoa powder for one month could improve blood sugar and other health outcomes related to diabetes. To test the first hypothesis, 30 overweight or obese volunteers who were at-risk for diabetes completed two blood tests. At the beginning of the tests, they consumed a meal replacement shake mixed with cocoa powder or a placebo powder. The participants had their blood drawn every hour for four hours. A week later, they repeated the same test with the alternative powder. Blood samples were analyzed for sugar levels and four hormones that are important for controlling sugar spikes. We found that the cocoa made no difference in blood sugar levels. However, we noticed that some of our participants had greater sugar spikes than others. Those who had large sugar spikes had deficient levels of certain hormones. Although our experiments showed that cocoa did not affect these hormones, other studies found that compounds similar to cocoa could increase these hormone levels. Future directions could include using a different meal or studying more adults deficient in these hormones. For the second hypothesis, 15 overweight or obese adults at risk for developing diabetes completed the study. They consumed cocoa powder or placebo powder beverages along with a controlled diet provided to them for one month (they did not know which treatment they received). We tested several outcomes related to digestion and metabolism including leakiness of the gut, ability to control blood sugar levels, and the ability of skeletal muscle to burn sugars and fats. Overall, cocoa did not seem to influence any of our outcomes. In conclusion, my experiments did not demonstrate any substantial effects of cocoa on blood sugar levels. However, the experiments did provide valuable information about hormone levels in overweight and obese adults. More research is needed to understand how cocoa can affect health outcomes for overweight or obese adults.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/82433 |
| Date | 07 September 2016 |
| Creators | Strat, Karen M. |
| Contributors | Human Nutrition, Foods and Exercise, Davy, Kevin P., Neilson, Andrew P., Davy, Brenda M., Frisard, Madlyn I. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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