What is the best age to start vitamin D supplementation to prevent rickets in breastfed newborns?

Abstract

Evidence-based answer: It's unclear what age is best to start vitamin D supplementation because no comparison studies exist. That said, breastfed infants who take vitamin D beginning at 3 to 5 days of life don't develop rickets (strength of recommendation SOR]: B, randomized trial). Starting infants on vitamin D supplementation at one to 36 months of age reduces the risk of rickets (SOR: B, a controlled and a randomized controlled trial).