Effects of Daily Beef Intake, as a Component of a Heart-Healthy Diet on Cellular Zinc

This study will examine whether daily beef intake will promote the absorption of dietary zinc into cells, leading to improved cellular zinc status and microvascular function. The study design will be a crossover comparison of a mixed diet including green leafy vegetables, fruits, whole grains, seeds, and nuts; with beef versus non-meat sources of additional protein and zinc, over two 4-week metabolic study periods. Outcomes will include cellular zinc status determined by erythrocyte zinc tracer exchange (primary), and microvascular function expressed as reactive hyperemia index (RHI). Previous studies have demonstrated that zinc tracer exchange with red blood cells (RBC) is highly sensitive to changes in zinc nutriture. Thus, cellular zinc status will be determined using a novel and cost-effective adaptation of this approach, modeling zinc tracer exchange with freshly-sampled RBC. As intracellular zinc can regulate vascular tone, microvascular function will be measured, using digital peripheral tonometry, will be used as a functional index of both cellular zinc status and vascular health.