Studies in tropical countries revealed a high prevalence of vitamin D insufficiency. The French recommendations did not differentiate between overseas and mainland areas in terms of vitamin D intake. However, the prevalence of vitamin D supplementation in infants in the French overseas territories is unknown.

The primary objective of the study was to assess the prevalence of vitamin D supplementation in infants aged 4 to 9 months in a tropical overseas region. Secondary objectives were to assess compliance, adherence and factors influencing vitamin D supplementation.

We conducted a cross-sectional study of infants born in La Réunion, a French overseas department in Indian Ocean. We interviewed the parents of all newborns born at term during a three-month period in 2022.

Among the 323 term infants included, the prevalence of vitamin D supplementation at 4 to 9 months of age was 52 %. Compliance to guidelines was 44.3 %. Factors that were significantly and positively associated with vitamin D use at 4 to 9 months of age were: information about vitamin D supplementation by caregivers before leaving the maternity ward, subscription to a supplementary health insurance, and follow-up by a pediatrician. Infants whose parents reported colic and the use of supplements were significantly more likely to discontinue vitamin D supplementation

Vitamin D supplementation in these infants born in an overseas territory was not in line with current national recommendations.