Why do babies and older children need vitamin d?

PEOPLE need it: Not just babies and children. The reason we need it is that our skin makes it when exposed to sunlight in the proper wavelength. When you live in a temperate climate and spend much of your time indoors and/or clothed, you are likely deficient. Vitamin D isn't just for bones. It acts as a hormone that helps to regulate the immune system, and you shouldn't be without it.

For good health: All humans need vitamin d. Unless you or your child is out in the sun when it is strong enough to get a slight sunburn, you will not have enough vitamin d. Vit d helps prevent infections including colds and the flu. It may also help prevent diabetes and obesity in children and adults.

Deficiency: Babies are dependent on milk , and breast milk is deficient in Vit D, hence the need for supplementation .