2009 Annual Report
1a.Objectives (from AD-416)
To determine if black tea antioxidants reduce oxidative damage and inflammation, and improve endothelial function and lipoprotein profile in cigarette smokers, and to determine the relative antioxidant effect of caffeine and tea flavanoids, to determine acute effects of drinking green, oolong, and black tea and other sources of polyphenols on insulin sensitivity, plasma antioxidant status, plasma triglyceride concentration, and whole body cytokine response of diabetics following consumption of a moderately high glycemic meal, and to determine if longer-term consumption of green, oolong, and black tea and other sources of polyphenols improves plasma antioxidant status, cardiovascular disease risk factors and glucose metabolism for individuals at risk for type II diabetes (prediabetics).
1b.Approach (from AD-416)
Dietary intervention studies will be conducted with human volunteers who are increased risk for chronic, degenerative diseases, such as diabetes, cardiovascular disease, cancer and obesity. Dietary interventions will focus on sources of polyphenols that may decrease macromolecular and physiological oxidative stress and decrease inflammation.
Previous studies have suggested that different types of protein can influence energy expenditure, which can impact obesity, and blood glucose regulation, which can impact diabetes. A clinical study was completed in this reporting period which investigated the interactions among soy and whey proteins and simple carbohydrates on energy expenditure, oxidation of protein, fat, and carbohydrate; glucoregulatory control; and carbohydrate absorption. Analysis of the data revealed that when whey protein was consumed with lactose, the amount of blood glucose was lower than when soy protein was consumed with lactose. However, when whey protein or soy protein were consumed with sucrose as the carbohydrate source, there was no difference in blood glucose response. In addition, data analysis was completed from a clinical study to determine the energy value of fiber and the effect of fiber on microbiota composition of the colon.
In summary, during the 5-year term of this project, clinical studies have been conducted investigating the role of dietary components on biomarkers of inflammation and risk factors for chronic disease. Commodities and food components studied included cocoa and tea polyphenols, protein, and fiber. These studies have provided new insights into how diet modulates disease risk and are of interest to producers, food manufacturers and health care practitioners.
Dietary food components to improve blood sugar in at-risk individuals. The incidence of both prediabetes and diabetes is increasing, and their health care costs are skyrocketing. Several clinical studies were conducted in at-risk populations with different sources of dietary polyphenols, including those from tea and cocoa, and different types of dietary proteins. While the polyphenols found in oolong tea did not improve blood sugar control, the green tea did improve glucose control compared to polyphenols found in cocoa. In combination with lactose, whey protein compared to soy protein reduced blood sugar. These results can be used in making evidence-based dietary recommendation for foods.
Energy value of fiber. For regulatory and health-promotion reasons, knowing the energy value of fiber is important, yet there are few data available for most types of dietary fiber. With the advent of innovative dietary fibers through new food processing technologies, research in this area has become increasingly important. A study to determine the energy value of resistant maltodextrin, which is a soluble dietary fiber with desirable functional properties, was conducted. These data are used by food manufacturers in order to meet food labeling requirements related to the energy value of their products. Since resistant maltodextrin is produced from cornstarch, it is a value-added product that could be of benefit to corn producers and processors.
Chen, S.C., Judd, J.T., Kramer, M.H., Meijer, G.W., Clevidence, B.A., Baer, D.J. 2009. Phytosterol intake and dietary fat reduction are independent and additive in their ability to reduce plasma LDL cholesterol. Lipids. 44(3):273-281.