Plasma zinc levels throughout pregnancy: a study in Jamaican women with relevant aspects of nutrition - abstract

ABSTRACT

In a prospective study, plasma zinc levels were determined by atomic absorption spectrophotometry in 135 Jamaican women over a two-year period. A total of 1,237 such determinations were made at fixed intervals throughout pregnancy. Zinc being an essential trace element with a wide physiological role in many aspects of metabolism, supplementary studies on the relationship between zinc, folic acid, vitamin A and dietary intake in general were undertaken. Results (Table) show that plasma zinc levels were lowered during pregnancy, moreso during the second trimester the levels rise significantly during labour and then fall rapidly towards normal during the puerperium. Daily dietary zinc intake was of the order of 8-10 mg/day (the RDA for pregnancy being 15 mg/day) while protein intake averaged 67 gm/day (the RDA for protein being 80-90 gm/day). Clinical and laboratory investigations revealed no signs of any dietary deficiency among the patients. Average weight gain in pregnancy was 12 kg. Plasma, vitamin A and red cell folate levels were within normal ranges in all patients, indicating that there was no state of zinc deficiency interfering with the absorption of these vitamins. Viewed together, all the facts of this study suggest that the pattern of the fall of plasma zinc in pregnancy is a normal physiological change not related to socio-economic status, parity or age. It is concluded that the lowered plasma zinc observed in pregnancy does not reflect a state of true deficiency nor even a state of inadequate dietary zinc intake; it is most likely due to the heavy demand for zinc in the developing foetal tissues and by the expanding maternal blood volume (AU)