High-dose vitamin D supplements are not associated with linear growth in a large Finnish cohort.

High vitamin D intake in childhood has been suggested to have an adverse influence on linear growth. In Finland, in the mid-1960s the official recommendation for infant vitamin D supplementation was 2000 IU/d (50 μg/d). We investigated whether high-dose vitamin D supplementation in infancy was associated with subsequent growth in height. We used data from a prospective population-based birth cohort study including all children due to be born in the 2 northernmost provinces in Finland in 1966 (12,058 live-births, coverage 96%). Information on each participant's height was collected at birth and ages 1, 14, and 31 y, as were possible confounding factors (data for analyses available from 10,060 singletons). Information on the frequency and dose of vitamin D supplementation was collected in 1967 when participants were 1 y of age. A weak association was found between frequency of vitamin D supplementation with greater height at age 1 y (P = 0.005), which was explained by birth characteristics and maternal and social factors (adjusted P = 0.34). Neither frequency nor dose of vitamin D supplementation was associated with height at 14 or 31 y (P > 0.13). To conclude, contrary to proposed evidence suggesting that vitamin D has a negative influence on growth rate at a dosage of ~2000 IU/d, supplementation at this level in the Northern Finland Birth Cohort was not associated with reduced height at any age studied.