The Effects of Vitamin D Supplementation During Infancy on Growth During the First Two Years of Life.
The relationship between maternal and infant vitamin D and early childhood growth remains inadequately understood.To investigate how maternal and child 25-hydroxyvitamin D [25(OH)D] and vitamin D supplementation impact growth during the first 2 years of life.A randomized, double-blinded intervention study.A single-center study from pregnancy until offspring age 2 years.Altogether 812 term-born children with complete data, recruited at Maternity Hospital.Children received daily vitamin D3 supplementation 10 μg (Group-10) or 30 μg (Group-30) from age 2 weeks to 2 years.Anthropometry and growth rate at age 1 and 2 years.Toddlers born to mothers with Pregnancy 25(OH)D >125 nmol/L were at 2 years lighter and thinner than the reference group with 25(OH)D 50-74.9 nmol/L (P<0.010). Mean 2-year 25(OH)D concentrations were 87 nmol/L in Group-10 and 118 nmol/L in Group-30 (P<0.001). When Group-30 was compared with Group-10, difference in body size was not statistically significant (P>0.053), but Group-30 had slower growth in length and head circumference between 6 months and 1 year (P<0.047), and more rapid growth in weight and length-adjusted weight between 1 and 2 years (P<0.043). Toddlers in the highest quartile of 25(OH)D (>121 nmol/L) were shorter (mean difference 0.2 SD score (SDS), P=0.021), lighter (mean difference 0.4 SDS, P=0.001) and thinner (in length-adjusted weight) (mean difference 0.4 SDS, P=0.003) compared with the lowest quartile (<81.2 nmol/L).Vitamin D and early childhood growth may have an inverse U-shaped relationship.