ZINC LEVELS IN MATERNAL MILK - THE INFLUENCE OF NUTRITIONAL-STATUS WITH RESPECT TO ZINC DURING THE 3RD-TRIMESTER OF PREGNANCY

Objective: To study the relationship between nutritional status with r espect to zinc during the third trimester of pregnancy and levels of t he same mineral in transition milk (days 13 and 14 of lactation) and m ature milk (day 40 of lactation). Design: Longitudinal study. Subjects : A group of 57 healthy, lactating mothers aged between 18 and 35 y (2 7 +/- 3.7) whose pregnancy and labour were attended by the Department of Obstetrics and Gynaecology of Cuenca INSALUD Hospital, Spain. Inter ventions: Zinc intake during the third trimester was determined by rec ording the consumption of foods over a five day period and by register ing zinc provided by dietary supplements. Zinc levels in maternal seru m during this stage of pregnancy, and in transition and mature milk, w ere determined by atomic absorption spectroscopy. Results: During preg nancy all subjects showed zinc intakes lower than those recommended. O nly one pregnant subject took a supplement that provided extra zinc (1 mg/d). Subjects with an intake of lower than 50% of that recommended (L) (43.9%) showed significantly lower serum and mature milk zinc leve ls than did those with higher intakes (H) (56.1%) [12.0 +/- 1.5 mu mol /L and 28.7 +/- 6.2 mu mol/L compared to 13.3 +/- 2.6 mu mol/L and 33. 1 +/- 8.0 mu mol/L respectively]. 56% of L subjects and 28.6% of H sub jects showed serum zinc levels of less than 12.2 mu mol/L. 8% of L sub jects and no H subjects showed less than 11.5 mu mol/L of zinc in mate rnal milk. Conclusions: The diet conditions maternal serum zinc levels during pregnancy and those of milk during lactation. Though all subje cts showed intakes clearly below those recommended, low levels in seru m or milk were much rarer. These results support the idea that there i s a need to reset the limits of normality for serum and milk zinc leve ls. Further work in this area may confirm that the present recommended intakes of zinc be modified.