Following an application from IDACE, submitted pursuant to Article 14 of Regulation (EC) No 1924/2006 via the Competent Authority of France, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to magnesium and contribution to normal development of bone. The food constituent, magnesium, which is the subject of the health claim, is sufficiently characterised. Contribution to normal development of bone is a beneficial physiological effect for infants and young children. A claim on magnesium and maintenance of normal bone in the general population has already been assessed with a favourable outcome. The Panel notes that the role of magnesium on bone mineralisation and homeostasis applies to all ages, including infants and young children (from birth to three years). The Panel concludes that a cause and effect relationship has been established between dietary intake of magnesium and contribution to normal development of bone. The following wording reflects the scientific evidence: “Magnesium contributes to normal development of bone”. The target population is infants and children up to three years.