Vitamin D supplementation during lactation to support infant and mother.

How human milk as the ideal infant nutrition lacks vitamin D activity leading to the severe bony deformities and muscle weakness of rickets has stymied scientists and clinicians for centuries. Recent understanding of human vitamin D requirements based on functional indicators of vitamin D activity demonstrate that the majority of humans, including lactating mothers, subsist in a vitamin D insufficient state. In this state, human milk provides inadequate vitamin D supply to the nursing infant. In contrast, with achieving maternal vitamin D sufficiency, human milk attains vitamin D activity equivalent to present infant oral supplementation. Current investigation of the role of vitamin D in diseases beyond bone health is revealing the significance of early life vitamin D sufficiency in establishing lifelong health.