Final answer:
Infants require about 100 units of vitamin D daily, which can be met by consuming at least one quart of vitamin D fortified infant formula. Lactating mothers need 400 units/day of vitamin D. Regular sun exposure also helps in the endogenous production of vitamin D3.
Step-by-step explanation:
Vitamin D Requirements for Infants and Lactating Mothers
The daily requirement of vitamin D for infants is approximately 100 units. A healthy infant may require 850 ml of milk daily, which indicates that consuming at least one quart of standard, vitamin D fortified infant formula would meet this requirement. Lactating mothers, on the other hand, have a higher need for vitamin D at 400 units/day. They also require additional calories, about 720 Kcal/day, to meet the energy demands of lactation.
Rich dietary sources of vitamin D include cod liver oil, fish liver oil, egg yolk, milk, and animal liver. Additionally, vitamin D3 can be endogenously produced through exposure to sunlight, which converts the sterol precursor, 7-dehydrocholesterol in the skin, into vitamin D3. This means that with regular sun exposure, dietary intake might not be as critical.
Foods fortified with vitamin D, such as milk and cereals, can help fulfill the daily requirements. For example, a 8-ounce glass of milk is typically fortified with about 100 IU of vitamin D. Moreover, the Recommended Dietary Allowances (RDA) suggest that infants under 1 year require 360-540 mg of calcium per day, which is significantly aided by the presence of vitamin D for absorption.