Older people (age 50 and over) have a higher risk of developing vitamin D deficiency because:
a- The ability of skin to convert 7-dehydrocholesterol to pre-vitamin D3 is decreased in older individuals.
Newborn infants who are exclusively breastfed require vitamin D supplements. Breast milk does not contain significant levels of the vitamin. Infant formula is generally fortified with vitamin D. so this requirement only applies to breastfed infants.