Milk Fat Intake and Metabolic Health Markers

Overview

This study investigates the effects of bioactive fatty acids in full fat dairy (whole yogurt), on insulin action, calorie needs, blood lipids, immune function, and body composition in normal and overweight male and female volunteers.

Saturated fats impair the action of insulin leading to abnormally high blood sugar levels that are characteristic of diabetes. Since milk fat is high in saturated fat, some experts advise against whole dairy products (e.g., milk and yogurt). However, bioactive fats, such as those which occur in milk fat, may be beneficial in the prevention of diabetes. Current data provide no compelling evidence that a moderate intake of saturated fat from milk fat increases the risk of diabetes. Milk fat contains a unique variety of bioactive fats, which may be beneficial and may counterbalance the potential negative effects of saturated fat. The investigators hypothesize that milk fat has favorable effects on metabolic risk markers associated with the metabolic syndrome. Therefore, this study tests the hypothesis that milk-fat intake will: (i) result in improved insulin sensitivity, (ii) favorably alter postprandial lipid metabolism, and (iii) result in lower circulating concentrations of pro-inflammatory markers. This study recruits 20-24 (total) female and male subjects in a blinded, randomized, crossover design consisting of two experimental diets (3 weeks each arm) based on a DASH-like diet (Dietary Approaches to Stop Hypertension diet) with % Energy (E%): 55 E% of carbohydrate, 15 E% of protein, and 30 E% of fat (9 E% saturated fatty acids (SFA), 15 E% of monounsaturated fatty acids (MUFA), and 6 E% of polyunsaturated fatty acids (PUFA)). One experimental arm contains milk fat and the other diet contains a control fat. A washout period represents an average US diet (48 E% of carbohydrate, 15 E% of protein and 37 E% of fat, kcal (16 E% of SFA, 14 E% of MUFA, and 7 E% of PUFA) is used to establish a level of normalization of the fatty acid intake among the subjects and to standardize the subject's physiologic state before each experimental diet. The two experimental diets are constructed to provide three servings of dairy in the form of either 1) regular whole (full-fat, 3.25%) yogurt or 2) fat-free yogurt supplemented with a control fat. The diets are identical in terms of menus, macro- and micronutrients, and fatty acid class composition (E%) with the exception of individual bioactive fatty acids, allowing for the comparison of the bioactive milk fatty acids to non-milk fatty acids. At the end of each period (initial washout period and each experimental diet) a frequently sampled intravenous glucose tolerance test is performed, blood is taken for fasting lipids (including lipoprotein profile), serum phospholipid fatty acid profiles, and inflammatory markers, and stool is sampled to examine the fecal microbiota composition.

Conditions

Interventions

Eligibility

Locations (1)

Outcomes