The purpose of this study is to determine whether snacks differing in fat amount and type result in changes in cardiovascular disease risk factors in men and women who have mildly elevated cholesterol levels. Our hypothesis is that a diet containing snacks rich in polyunsaturated fats lead to a more favorable cardiovascular disease risk profile than a diet containing snacks rich in saturated and trans fats or one containing low-fat snacks.
Behavioral: higher fat, high polyunsaturated fat diet
Behavioral: higher fat, high saturated and trans fat diet
Behavioral: lower fat diet
The overall goals of this study are to determine whether snack foods rich in polyunsaturated fats (PUFA) produce beneficial effects on cardiovascular disease risk compared to snacks rich in saturated fats (SFA) and trans fats and snacks rich in refined carbohydrates. The primary objective of this study is to determine the effects of substituting n-6 PUFA (linoleic acid) from snack chips for SFA/trans fat and refined carbohydrate on serum lipids -principally LDL-C - and lipoproteins in moderately hypercholesterolemic men and women. A secondary objective is to assess effects on lipoprotein subclass particle size, intramyocellular lipids, and C-reactive protein (CRP). Forty-two men and women will be recruited to participate in a randomized, crossover, controlled feeding experiment for 3 periods of 4 weeks each. Each feeding phase will be separated by an 8-week washout period. The control diet will be a National Cholesterol Education Program Step 1 diet consisting of approximately 30% energy from total fat, <10% energy from SFA, 5% energy from PUFA, 15% energy from monounsaturated fatty acids (MUFA), 1% energy from trans fat, 55% energy from carbohydrates, and 15% energy from protein. To achieve an isocaloric substitution with PUFA, 300 kcal coming from low-fat, high-carbohydrate snacks will be removed from the Step 1 diet (NCEP diet) and replaced with 300 kcal of PUFA-rich snacks (LO diet). Similarly, 300 kcal from snacks rich in SFA/trans fat will replace the same 300 kcal from the high-carbohydrate from the Step 1 diet for the high SFA diet (SF diet). Subjects will consumed all foods provided by the GCRC and nothing else during each feeding phase. Breakfast and lunch meals will be consumed at the GCRC on weekdays and breakfast on Saturdays. All other meals will be packed and consumed at home. The primary study variable will be serum/plasma LDL-cholesterol. Secondary variables will include lipids and lipoproteins including total cholesterol (TC), HDL-cholesterol, VLDL-cholesterol, and triglycerides, and intramyocellular lipids. Exploratory variables will include assessment of lipid subclass particle size and CRP, a marker of systemic inflammation. Supportive variables will include fasting blood glucose and insulin, percent body fat mass, blood pressure and demographic information. All variables will be measured at baseline and endpoint of each feeding phase.