Breastfeeding as the sole source of milk for 6months and adolescent bone mineral density.

Abstract

The aim of the study is to assess the role of breastfeeding BF on adolescent bone mineral density (BMD) in a cohort prospectively followed since infancy. We studied 679 participants from an infancy iron deficiency anemia preventive trial in Santiago, Chile, followed to adolescence. Breast and bottle feeding were ascertained weekly from 4 to 12months. At 16years, whole body BMD was assessed by DEXA. Using linear regression, we evaluated associations between BF duration and BF as the sole source of milk and adolescent BMD z-score, adjusting for possible infancy, adolescent, and background confounders. Mean birth weight and length were 3.5(0.3)kg and 50.7(1.6)cm. For at least 6months, BF was the sole source of milk for 26.3% and with supplementation for 36.7%. For 37%, BF was provided for less than 6months. Mean 16-year BMD z-score was 0.25 (1.0). Covariates included male sex, birth length, and gestational age. BF as the sole source of milk ≥6months, compared to BF<6months, was associated with higher adolescent BMD z-score adjusting for covariates (β=0.29, p<0.05). Mixed BF was not significantly related to adolescent BMD z-score (β=0.06, p=0.47). For every 30days of BF as the sole source of milk, adolescent BMD z-score increased by 0.03 (p=0.01). BF without formula supplementation for at least 6months was associated with higher adolescent BMD z-score and a suggestive trend in the same direction for BMD suggests that exclusivity and duration of BF may play a role in adolescent bone health.