Background: The aim of the present study was to investigate whether such supplementation impairs the zinc status of pregnant women or the zinc content of maternal milk.
Material and methods: Fifty seven women were studied during pregnancy and lactation. Zinc, iron and folate intakes were monitored during the third trimester of pregnancy using a five day food record and by registering intake of the same in the form of dietary supplements. Zinc levels were determined, using flame-atomic-absorption spectrophotometry, in serum during the third trimester of pregnancy, in transition milk (day 13-14 of lactation), and in mature milk (day 40 of lactation).
Results: 1.8% of pregnant women took zinc supplements whilst 7% took folate supplements. However, 100% of subjects showed zinc intakes (the sum of dietary and supplementary intakes) lower than those recommended. 87.7% showed the same for folate intake, 29.8% of pregnant women took iron supplements. When dietary and supplementary intakes were added, 26.3% of subjects showed iron intakes of over 200% of those recommended. Pregnant women with iron intakes in the third trimester of pregnancy of over 200% those recommended, showed lower serum zinc levels during the third trimester and, at a later date, lower mature milk zinc levels than did subjects with lower iron intakes.
Conclusions: The combined dietary and supplementary intake of iron in some subjects provided total intakes of over 200% those recommended. Though this might be associated with an improvement in iron status it may impair those of zinc. Subjects with an intake of iron of over 200% of that recommended showed significantly lower serum and mature milk zinc levels than did those with lower iron intakes. It is suggested that the nutritional status of pregnant women should be carefully monitored and supplementation tailored to the needs of each individual.