(P17-031-24) Effects of Daily Beef Intake, as a Component of a Heart-Healthy Diet on Cellular Zinc Status and Microvascular Function

Objectives: Beef is a dietary source of highly bioavailable zinc. Zinc, in turn, is needed for the widest range of cellular metabolic functions, including those supporting cardiometabolic health, of any single micronutrient. The risk of zinc deficiency tends to increase with age. Our objective was to test the hypothesis that the intake of 4 oz. of beef daily for four weeks, within a heart-healthy dietary pattern composed of fresh fruits, vegetables, whole grains, seeds, and nuts, would improve cellular zinc status and microvascular function in older adults, vs. a similar amount of  zinc and protein from non-meat sources.

Methods: The study followed a crossover design. Subjects were randomized to consume a stew containing 4 oz. of beef daily for 4 weeks, or a control stew with similar zinc, protein, and energy content from non-meat sources. After a 6-week washout period, each subject crossed over to repeat the 4-week intervention on the other treatment. Cellular zinc status was determined by the exchange of a zinc-65 radiotracer with erythrocytes in recently drawn venous blood. Microvascular function was determined by peripheral arterial tonometry.

Results: The study is ongoing. Results are presented for the initial six subjects. Four weeks of beef intake tended to increase the exchange of the zinc tracer with erythrocytes vs. control (p = 0.068). Effects on microvascular tone were not observed, however there was a significant reduction in systolic and diastolic blood pressure with 4 weeks of beef intake vs. control (p = 0.003 and p = 0.046, respectively). In addition, beef intake increased circulating levels of HDL cholesterol vs. control (p = 0.04), resulting in a trend towards a reduced total cholesterol to HDL cholesterol ratio (p = 0.07).

Conclusions: Preliminary data show 4 oz. daily beef may increase the direction of zinc to cellular compartments, when compared with non-meat foods containing similar amounts of zinc and protein. Moreover, observed changes in cholesterol and blood pressure demonstrate that regular beef intake may enhance these positive effects of a heart-healthy dietary pattern.  Further study is indicated to determine the mechanisms and optimal dietary context for beef to promote health via its impacts on cellular zinc metabolism.

Funding Sources: Funded by National Cattlemen's Beef Association, a contractor to the Beef Checkoff.