The effect of increasing dietary zinc on the activity of superoxide dismutase and zinc concentration in erythrocytes of healthy female subjects.

Zinc has many diverse functions and is essential for growth and development. Although a number of dietary constituents inhibit its absorption, a reliable index of zinc intake and/or bioavailability remains to be identified. The aim of this study was to test the hypothesis that recent changes in zinc intake and/or bioavailability are reflected in a subfraction of erythrocytes. Six healthy female volunteers were asked to supplement their diet with 50 mg of elemental zinc per day for 12 days. Venous blood samples were obtained before and during supplementation at 4-day intervals. A subfraction of erythrocytes was isolated from each sample and zinc concentration was measured in this subfraction, in the unfractionated erythrocytes and in the plasma. These showed no significant temporal change. Erythrocyte superoxide dismutase (E-SOD), a marker of copper status, showed a significant 20% decrease (P < 0.02) in its activity in both the subfraction and the unfractionated erythrocytes following supplementation. Hence, a detrimental effect on copper metabolism (as measured by the marker enzyme E-SOD) can be detected within 12 days of supplementation with a moderate amount of zinc.