Milk Intake, Calcium and Vitamin D in Pregnancy and Lactation: Effects on Maternal, Fetal and Infant Bone in Low- and High-Income Countries
Calcium and vitamin D are essential for bone growth and maintenance. Among the bone-forming minerals, dietary calcium supply is close to biological requirements and may be limiting in some parts of the world where there are few rich dietary sources of calcium, particularly for children, and women during pregnancy and lactation. Animal milk is a rich source of calcium and, in countries where milk is fortified with vitamin D, a contributor to dietary vitamin D intake. Current evidence indicates that, in the human, there are physiological mechanisms that support the necessary calcium fluxes across the placenta and mammary gland and that are unresponsive to increases in calcium intake. This applies across the range of dietary calcium intakes recorded in healthy individuals. In contrast, although there is unlikely to be an additional requirement for vitamin D during pregnancy and lactation, many women have poor vitamin D status. This places them at risk of osteomalacia and their infants at risk of rickets, osteomalacia, compromised skeletal growth and other outcomes. There needs to be increased awareness among policy-makers, health professionals and the public about the importance of safe UVB sunshine exposure and consumption of dietary vitamin D by women of reproductive age at risk of vitamin D deficiency.