文本框: Calcium Requirements of the mother and her infant Ann Prentice MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, CB1 9NL,UK Objective:About 200 mg/d of calcium is transferred from the mother to the baby across the placenta at the end of pregnancy and into breastmilk during breastfeeding. This represents a sizeable proportion of the usual daily intake of this mineral for many mothers. Concerns, therefore, are often expressed that an inadequate calcium intake by the mother during pregnancy and lactation could lead to poor growth and skeletal development of the infant and could compromise her own long-term bone health. Methods:Several of these have been conducted by my research group and have included parallel investigations of mothers and their infants in Cambridge, England and in Keneba, The Gambia, West Africa. These mothers differ in a number of respects, most particularly in their calcium intake in pregnancy and lactation, which averages about 1250 mg/d in Cambridge and300-400 mg/d in Keneba. Results:Observational and supplementation studies have demonstrated that a higher calcium intake by the mother during lactation does not affect breast-milk calcium or alter the temporary changes that occur in the mother’s skeleton or metabolism.There is, therefore, little to suggest that the calcium intake of a breastfeeding mother influences the amount of calcium supplied to her baby, or affects the growth of her infant. The skeletal changes experienced by the mother during breastfeeding are temporary and are unlikely to jeopardise her bone health in the long-term. Conclusion:In pregnancy, the mother’s body increases the efficiency with which she retains calcium and there is little evidence that an increase in her calcium intake is necessary. However, there is limited evidence that a very low calcium intake by the mother during pregnancy may affect calcium transfer across the placenta and subsequently into breastmilk, as well as potentially increasing the risk of pregnancy-induced hypertension in the mother and a higher blood pressure in the child. Further work is needed, but current evidence suggests that, while good calcium nutrition should be encouraged at all ages, most women do not need to increase their calcium intake during pregnancy and breast-feeding, and that breast-milk provides all the calcium the infant requires during early infancy. It is possible, however, that a very low calcium intake in pregnancy may have some long-term effects on infant growth and health.