Vitamin B12 and/or folic acid supplementation on linear growth; a 6 years follow-up study of a randomised controlled trial in early childhood in North India.

Folate and vitamin B12 are essential for growth. Our objective was to estimate their long-term effects on linear growth in North Indian children. This is a follow-up study of a factorial designed, double-blind, randomized placebo-controlled trial in 1,000 young children. Starting at 6-30 months of age, we gave folic acid (∼2 RDAs), vitamin B12 (∼2 RDAs), both vitamins, or a placebo daily for six months. Six years after the end of supplementation, we measured height in 791 children. We used the plasma concentrations of cobalamin, folate, and total homocysteine to estimate vitamin status. The effect of the interventions, the association between height-for-age z-scores (HAZ) and baseline vitamin status, and the interactions between supplementation and baseline status were estimated in multiple regression models. Mean (SD) age at follow-up was 7.4 (0.7) years (range 6 to 9 years). There was a small, non-significant effect of vitamin B12 on linear growth and no effect of folic acid. We observed a subgroup-effect of vitamin B12 supplementation in those with plasma cobalamin concentration < 200 pmol/L (P interaction = 0.01). The effect of vitamin B12 supplementation in this group was 0.34 HAZ (95% CI: 0.11-0.58). We found an association between cobalamin status and HAZ in children not given vitamin B12 (P interaction = 0.001). In this group, each doubling of the cobalamin concentration was associated with 0.26 (95% CI: 0.15 to 0.38) higher HAZ. Suboptimal B12 status in early childhood seemingly limits linear growth in North Indian Children.