Lack of Effect of Graded Doses of Vitamin D on Bone Metabolism of Breastfed Infants

Objective: A range of doses of supplemental vitamin D has been shown to be effective in preventing rickets in breastfed infants, but the effect of different doses of vitamin D on bone metabolism and mineral content has not been delineated. Methods: In a randomized trial, breastfed infants received from 2 to 9 months daily supplements of vitamin D in doses of 200 IU/d, 400 IU/d, 600 IU/d or 800 IU/d. Measures of bone metabolism (plasma) were determined periodically and bone mineral content (DXA) was determined at study entry and at the end of winter when infants were 5.5 to 9 months old. The main findings have been reported; here we report findings related to bone metabolism. Results: There were no consistent meaningful effects of vitamin D dose on markers of bone metabolism. Some markers showed changes with age. Bone mineral content increased with age but showed no effect of vitamin D dose. Conclusion: Vitamin D in daily doses from 200 IU/d to 800 IU/d had no measurable effect on bone mineral content or bone metabolism of breastfed infants.