Vitamin D requirements
Because vitamin D may be supplied either by ingestg it in foods or supplements or by exposure to certain wavelengths of sunlight, its requirement has been difficult to determine.
In infants 100 IU (2.5 mcg) of vitamin D per day prevents rickets and provides for adequate calcium absorption, normal bone mineralization, and a satisfactory growth rate. However, because increased growth and better calcium absorption resulted from feeding 300 IU to 400 IU (7.5 mcg-10.0 mcg) daily, experts recommend 10 mcg (400 IU) of vitamin D per day for infants and young children, birth through 6 years of age. These recommendations apply to both formula-fed and breast-fed infants. The premature infant who is growing rapidly and is usually not exposed to sunlight for a considerable length of time is more prone to develop rickets than the full term infant; for this reason he should be assured an adequate amount of vitamin D
Because there is little information regarding vitamin D requirements in older children and adolescents and because rickets is practically nonexistent in this age group. However, some recommend a daily intake of 10 mcg (400 IU) of vitamin D from birth through age 18, 7.5 mcg (300 IU) during years 19 to 22, and 5 mcg (200 IU) for adults over the age of 22 years. Although adults are expected to meet their requirement through exposure to sunlight under most conditions, certain circumstances and customs may necessitate a dietary source of vitamin D. During pregnancy and lactation, 10 mcg (400 IU) daily are recommended.
