The fluxes of the primary bone-forming minerals,
calcium,
phosphorus,
magnesium and
zinc, across the placenta and through breast milk place considerable demands on maternal
mineral economy. Increases in food consumption, elevated gastrointestinal absorption, decreased
mineral excretion and mobilization of tissue stores are several possible
biological strategies for meeting these extra
mineral requirements. This paper presents a review of the evidence on the extent to which these strategies apply in the human situation, the mechanisms by which they occur, the limitations imposed by maternal diet and
vitamin D status and the possible consequences for the growth of the infant and bone health of the mother. On the strength of current evidence it appears that pregnancy and lactation are associated with physiological adaptive changes in
mineral metabolism that are independent of maternal
mineral supply within the range of normal dietary intakes. These processes provide the minerals necessary for fetal growth and breast milk production without requiring an increase in maternal dietary intake or compromising maternal bone health in the long term. This may not apply to pregnant women whose
mineral intakes or sunlight exposure are marginal. As a vehicle for promoting optimal growth and bone mineral content of infants, supplementation of lactating women with minerals or
vitamin D is unlikely to prove effective. The situation in pregnancy is less certain. Until more studies have been conducted, a precautionary case can be made for targeted supplementation of pregnant women who have very low intakes of
calcium or who are at risk of
vitamin D deficiency.