Understanding Vitamin D Requirements During First 12 Months of Life
Science progresses continuously but not at a constant velocity. Today’s blog highlights the importance of thoughtful, deliberative discussion among scientists. Stimulated by a May peer-reviewed publication on the effects of vitamin D supplementation to infants during their first year, two letters were sent to the Editor of JAMA. Here is the story.
Using the classic gold standard scientific design, double-blind, randomized clinical trial (RCT), Gallo and colleagues followed 132 healthy, term, breastfed infants from Montreal, Canada who were randomized to receive vitamin D orally (400, 800, 1200 or 1600 IU/d) for 11 months. The primary objective was to establish a vitamin D dosage which would maintain a plasma 25(OH)D concentration ≥75 nmol/L. Within 3 months, all dosages achieved 25(OH)D concentrations above 50 nmol/L in 97% of infants. Only the 1600 IU/d achieved the primary outcome. 97% of infants achieved plasma 25(OH)D above 75 nmol/L. There were no significant differences in growth and bone mineral content among infants by dosage. It is noteworthy that the investigators administered vitamin D doses exceeding the Tolerable Upper Limit (UL) of 1000 and 1500 IU/d for infants 0 to 6 months (or 25 μg/d) and 6 months to 12 months (or 38 μg/d), respectively. The 1600 IU dosage was discontinued at 3 months because some children had 25(OH)D concentrations > 125 nmol/L, a risk factor for hypercalcemia, but there were no reported adverse events.
In a letter to the Editor, Sofiyan and colleagues criticize Gallo and associates for statistically adjusting for sun exposure using an index which not been properly validated. Differences in sun exposure could partially explain the wide variation in 25(OH)D levels following vitamin D supplementation. In their response, Gallo, Rodd and Weiler acknowledge the limitations in estimating sun exposure, especially in people with differing skin pigmentation.
As is often the case in science, more research is needed.
Gallo S, Comeau K, Vanstone C, Agellon S, Sharma A, Jones G, L’Abbe M, Khamessan A, Rodd C, Weiler H. Effect of different dosages of oral vitamin D supplementation on vitamin D status in healthy, breastfed infants, a randomized study. 2013 JAMA doi:10.1001/jama.2013.3404
Sofiyan A, Nanan RKH, Habil M. Vitamin D supplementation during first 12 months of life. 2013 JAMA doi:10.1001/jama.2013.124263
Gallo S, Rodd C, Weiler H. Vitamin D supplementation during first 12 months of life. 2013 JAMA doi:10.1001/jama.2013.124272