Calcium intakes and bone densities of lactating women and breast-fed infants in The Gambia

Abstract

The calcium required for breast-milk production and infant growth can be a substantial proportion of dietary intakes especially in regions of the world were calcium consumption is low. Insufficient calcium supply might lead to maternal bone loss, reduced breast-milk calcium secretion and impaired infant bone growth. However, changes in calcium absorption and excretion may be sufficient to allow these requirements to be met without affecting maternal or infant health. A limited number of studies have investigated changes in maternal bone mineral, absorption, excretion and metabolism during lactation but few have addressed whether any changes are influenced by calcium intakes. Ongoing detailed research by the MRC Dunn Nutrition Unit in a rural area of The Gambia amongst mothers and infants with habitually low calcium intakes will provide valuable information about calcium needs during lactation and growth.

PIP: The limited published data on the extent to which human lactation is associated with alterations in calcium and bone metabolism and whether any changes are influenced by maternal diet are reviewed. The evidence is equivocal and difficult to interpret as, in general, no attempts have been made to detail the magnitude of the calcium stress on the mothers. Insufficient calcium supply might lead to maternal bone loss, reduced breast-milk calcium secretion, and impaired infant bone growth. However, changes in calcium absorption and excretion may be sufficient to allow these requirements to be met without affecting maternal or infant health. Calcium and bone metabolism during human lactation and the impact of maternal diet affect bone mobilization. Metabolic adjustments may occur in lactation to ensure that calcium is conserved and channelled to the breast for milk production. If insufficient calcium is available during lactation, the composition, and possibly volume, of breast-milk may be impaired. Inadequate calcium intakes during childhood are likely to lead to diminished growth and reduced bone mineral contents. Ongoing research by the MRC Dunn Nutrition Unit, Cambridge, United Kingdom, included recent studies in the poor, rural village of Keneba, the Gambia, in order to provide more fundamental information on calcium requirements for growth and lactation in communities where the diet is constitutionally low in calcium. The dietary studies demonstrated that the calcium intakes of rural Gambian mothers and infants are habitually low given the predominantly vegetarian diet. The calcium intakes of mothers averaged around 400 mg/d (10 mmol/d). The contribution of breast-milk to total intakes decreased with increasing age but was always substantial, 93% at 2 months; 54% at 9 months; 40% at 15-18 months. These descriptive studies suggest that the low calcium intakes of rural Gambians may be sub-optimal during growth and lactation.