ABSTRACT
Effects of dietary zinc supplement during lactation on maternal plasma zinc and milk zinc concentrations through 5 months of lactation were examined. One hundred and thirty eight healthy lactating mothers received a weekly 100 mg elemental zinc supplement [ZG, n = 67] or placebo [PG, n = 71] starting one week postpartum in a double blind, randomized design. Milk and plasma zinc concentrations were determined by atomic absorption spectrophotoineter. During the course of study, there was not a significant difference between ZG and PG groups in dietary zinc and energy intake. The mean plasma zinc concentration during the 1st week and 5th month were 134 +/- 49.1 and lI5.6 +/- 23ug/dl [p=0.005] for PG group, respectively: that of the ZG group these figures were 124.9 +/- 52.8 and I21 +/- 27.1ug/dl [p=0.38,], respectively. The mean serum alkaline phosphatase concentration of the 1st week and 5th month were 94.8 +/- 3 7 and 92.6 +/- 29.9 iu/l for PG group, respectively: that of the ZG group these figures were 90.5 +/- 36 and 90 +/- 29 iu/l [p=0.21], respectively. Milk zinc concentration declined significantly over the course of study for two groups, with the sharpest decline occurring during the first 2 months. The mean monthly zinc concentration of ZG group declined from 310 +/- 138 during the 1st week to l18 +/- 64pg/dl at 5th month [declined by 52%]. Corresponding means for PG group were 322 +/- 1 61 and l09 +/- 70ug/dl [declined by 60%], respectively. Milk zinc concentration was significantly different between two groups for 3 and 4 months. A similar study, however, with different zinc dose and administration manner, in zinc marginal deficient lactating mothers is needed to assess the impact of zinc supplementation on milk zinc concentrations