The selenium status of a group of 23 lactating and 13 nonlactating women was assessed from 37-wk gestation through 6-mo postpartum. The mean overall dietary Se intake of both groups of women was 80 +/- 37 micrograms/d. Plasma and erythrocyte Se levels were lower in the lactating than in the nonlactating mothers both before and after parturition. Breast-milk Se concentrations fell from 20 micrograms/L (0.25 mumol/L) at 1-mo postpartum to 15 micrograms/L (0.19 mumol/L) at 3- and 6-mo postpartum. A weak (r = 0.38) but statistically significant (p less than 0.025) relationship was observed between maternal plasma Se level and breast-milk Se concentration. The dietary Se intake of these lactating North American women appears sufficient to maintain satisfactory Se nutriture in their breast-fed infants during the first 6 mo of lactation.

Glutathione peroxidase activity in platelets increased stepwise in selenium-depleted rats that were repleted with graded levels of dietary sodium selenite. In a 3-phase depletion/repletion/depletion feeding study, glutathione peroxidase activity was similar in platelets and liver, which apparently contains the largest labile pool of selenium in the body. The activity of glutathione S-transferase (selenium-independent glutathione peroxidase) in platelets was low and was not affected by selenium deficiency, even though hepatic transferase was markedly elevated in selenium-deficient rats. Vitamin E deficiency did not affect activities of glutathione peroxidase or glutathione S-transferase in platelets or liver. Determination of glutathione peroxidase activity in platelets apparently is a promising technique for assessing selenium status and, possibly, for measuring selenium bioavailability.

The zinc status of a group of 23 lactating and 13 nonlactating women was assessed longitudinally from 37-wk gestation through 6 months postpartum. Dietary zinc intake was determined by chemical analysis of 3-day duplicate plate food composites. In addition, zinc concentrations were measured in plasma, erythrocytes, and breast milk. The mean dietary zinc intake of both groups of postpartum women as determined by direct analyses was 42% of the Recommended Dietary Allowances or less. The plasma and erythrocyte zinc concentrations were not significantly different between the lactating and nonlactating women. Plasma zinc concentration increased from the time of delivery to one month postpartum for both groups and did not significantly increase further through 6 months postpartum. Erythrocyte zinc decreased from delivery through 6 months postpartum for both groups. Breast milk zinc concentration decreased with the duration of lactation. The calculated zinc intake of infants from breast milk was less than 50% of the Recommended Dietary Allowances. There was no correlation of maternal dietary zinc intake or maternal plasma and erythrocyte zinc with the concentration of zinc in breast milk.