The effects of dietary folate and zinc on the outcome of pregnancy and early growth in rats

Abstract

1. The objective of the present study was to determine the effects of two levels of folic acid and two levels of zinc in the diets of rats during pregnancy and lactation. It addressed, among other things, the question of whether an inhibitory effect of folic (pteroylmonoglutamic) acid on Zn absorption might result in a secondary Zn deficiency in either the dams or the pups.2. A purified diet was given to four groups of female DNL (Norwegian) Hooded rats, before and during pregnancy and during lactation. It contained the four possible combinations of: no added folic acid or 100 μg added pteroylmonoglutamic acid/g, and 6·6 or 20·2 μg Zn/g. Pups and dams were killed on day 20 of gestation or on day 20 postpartum. Measurements of body-weights, food intakes, blood folate and tissue Zn levels were performed.3. The group with low Zn and low folate intake had a satisfactory reproductive outcome, and there were only minor effects of the supplements on body-weights.4. Additional folate greatly increased blood (erythrocyte and plasma) folate levels, but did not compromise tissue Zn concentrations. Zn supplementation also enhanced blood folate levels, for reasons which are not yet clear.5. There was a moderate enhancing effect of the Zn supplement on Zn levels in the livers and kidneys of pregnant dams, and the kidneys of lactating dams.6. If the conclusions can be extrapolated to humans, then the results provide some reassurance that a high folate intake from prenatal supplementation need not necessarily cause Zn depletion, and hence functional Zn deficiency in pregnant women and their offspring.