Zinc deficiency and dietary folate metabolism in pregnant rats

Five groups of pregnant Wistar rats (zinc-deficient diet without folate supplementation; folinic acid, folate monoglutamate, folate polyglutamate-supplemented groups receiving zinc-deficient diet; pair-fed groups as controls) were fed from day one of fertilization with a semisynthetic zinc-deficient diet containing 0.2 mg/kg of Zn in the diet for the 4 deficient groups and 100 mg/kg for the pair-fed group. After 20 days, the zinc status (plasma, liver, femoral bone) was significantly decreased in the zinc-deficient groups. The liver and plasma folate levels were lower in the zinc-deficient groups compared to the pair-fed group. Moreover, the folinic acid and the polyglutamate folate supplementations (100 mg/kg diet) did not normalize the folate status of the animals. Only the supplementation with folate monoglutamate led to correct folate levels in the pregnant rats. Nevertheless, no form of folate supplementation prevented fetal growth retardation in any of the zinc-deficient groups. These results indicate that zinc deficiency in pregnant rats decreases folate bioavailability of folinic acid, folate polyglutamates and, to a lesser extent, that of folate monoglutamate. However, no form of folate supplementation (i.e., folate monoglutamate) prevents fetal growth defect and the incidence of malformation in zinc-deficient rats.