Most adolescents and adults receive much of their necessary vitamin D from exposure to sunlight. Infants and young children, however, need to avoid direct sun entirely or be especially careful by always wearing sunscreen.
Make sure your child is eating foods that contain vitamin D naturally — fatty fish, fish oil and egg yolks — or that have been fortified with vitamin D, such as:
- Infant formula
- Cereals
- Milk
- Orange juice
Because human milk contains only a small amount of vitamin D, all breast-fed infants should receive 400 international units (IU) of oral vitamin D daily.
Source: http://www.mayoclinic.com