Red cell superoxide dismutase activity as an index of human copper nutrition.

Red cell superoxide dismutase (SOD) activity was evaluated as a biochemical index of copper nutrition in a double-blind study of 17 infants recovering from malnutrition and receiving marginal copper intakes. Children were paired on admission by sex, birth weight, nutritional status and antecedents of diarrhea and breast feeding. Nine served as controls receiving a copper sulfate supplement (80 micrograms/kg daily for 120 d; eight received a placebo and were supplemented only if plasma copper levels dropped below 90 micrograms/dl or on d 90 for at least 30 d. After copper supplementation there was a significant rise (paired t-test; P less than 0.05) in plasma copper (96 vs. 165 micrograms/dl); ceruloplasmin (33 vs. 50 mg/dl) and SOD (1073 vs. 1371 U/g Hb). After supplementation these values were similar to those of the controls. SOD was correlated with plasma copper (r = 0.78; P less than 0.001) and not with weight-for-age or weight-for-length. Addition of copper in vitro did not modify the SOD activity. Red cell SOD is a good marker of copper nutrition in humans and correlates well with plasma copper.