The Effects of Vitamin D Supplementation During Infancy on Growth During the First 2 Years of Life

Context: The relationship between maternal and infant vitamin D and early childhood growth remains inadequately understood. Objective: This work aimed to investigate how maternal and child 25-hydroxyvitamin D (25[OH]D) and vitamin D supplementation affect growth during the first 2 years of life. Methods: A randomized, double-blinded, single-center intervention study was conducted from pregnancy until offspring age 2 years. Altogether 812 term-born children with complete data were recruited at a maternity hospital. Children received daily vitamin D-3 supplementation of 10 mu g (group 10) or 30 mu g (group 30) from age 2 weeks to 2 years. Anthropometry and growth rate were measured at age 1 and 2 years. Results: Toddlers born to mothers with pregnancy 25(OH)D greater than 125 nmol/L were at 2 years lighter and thinner than the reference group with 25(OH)D of 50 to 74.9 nmol/L (P<.010). Mean 2-year 25(OH)D concentrations were 87 nmol/L in group 10 and 118 nmol/L in group 30 (P<.001). When group 30 was compared with group 10, difference in body size was not statistically significant (P>.053), but group 30 had slower growth in length and head circumference between 6 months and 1 year (P<.047), and more rapid growth in weight and length-adjusted weight between 1 and 2 years (P<.043). Toddlers in the highest quartile of 25(OH)D (>121 nmol/L) were shorter (mean difference 0.2 SD score [SDS], P=.021), lighter (mean difference 0.4 SDS, P=.001), and thinner (in length-adjusted weight) (mean difference 0.4 SDS, P=.003) compared with the lowest quartile (<81.2 nmol/L). Conclusion: Vitamin D and early childhood growth may have an inverse U-shaped relationship.