Dietary Protein Sources and Atherogenic Dyslipidemia

There is growing epidemiological evidence that consumption of red meat is associated with greater incidence of Cardiovascular Disease (CVD) than either white meat or non-meat foods. Research from our group has shown that a high saturated fat (SF) diet with a moderate red meat content selectively increases intermediate density lipoproteins (IDL) and larger low density lipoproteins (LDLs), which are more weakly associated with CVD risk than smaller LDLs. In contrast, the investigators have found that with a similar intake of SF, high beef consumption results in a preferential increase in small and medium LDL particles that are strongly related to CVD. To date, no studies have directly compared the lipoprotein effects of red meat with that of other food sources of protein in the context of both high and low saturated fat intake. The overall objective of this project is to test the hypothesis that the effects of SF on lipoprotein markers of CVD risk are influenced by sources of dietary protein. The investigators hypothesize that adverse effects of SF on plasma levels of LDL-cholesterol (C), apolipoprotein B (apo B), and atherogenic LDL particles are greater in a diet with a high content of red meat than in diets in which the major proteins are from white meat (poultry) or non-meat sources. The investigators propose a clinical trial in which 180 healthy men and women will be randomized to high SF or low SF diet groups, and within each group, consume diets with equivalent amounts of protein from red meat, white meat, and non-meat sources for 4 wks each in random order. Specifically, the investigators will test whether: (1) With high SF, the red meat diet, compared to the other protein sources, will result in higher levels of LDL-C, apoB, small and medium LDL, and total/high density lipoprotein (HDL)C; (2) With low SF, dietary protein source will not be related to any of these measurements; (3) With both the white meat and non-meat protein diets, increased LDL-C with high vs. low SF will be due primarily to increases in large LDL, whereas with red meat the additional increase in small and medium LDL will result in greater increases in plasma apoB and total LDL particle number. Aim 4 will test hypotheses that increases in small and medium LDL with high SF plus red meat are related to increased activity of hepatic lipase, a key determinant of small LDL production, and that increases in large LDL induced by high SF are related to suppression of LDL receptors. The investigators will also assess the effects of protein source and saturated fat content on markers of insulin resistance, inflammation and endothelial function.