Background: Breastfeeding has been associated with a protective effect against cardiovascular disease. Higher cardiorespiratory fitness during childhood is associated with healthier cardiovascular profile later in life.
Objectives: The objective was to examine the association of exclusive breastfeeding duration with fitness in children and adolescents and to test the role of body composition and sociodemographic factors in this relation.
Design: At the time of the study, exclusive breastfeeding duration was reported by mothers and grouped into 4 categories: exclusively formula fed or breastfed for <3, 3-6, or >6 mo. Fitness was determined by a maximal cycle-ergometer test in 1025 children (aged 9.5 ± 0.4 y) and in 971 adolescents (aged 15.5 ± 0.5 y) from Estonia and Sweden.
Results: Longer duration of breastfeeding was associated with higher fitness regardless of confounders [+5.1% L/min; country, sex, age, pubertal status, and BMI (adjusted P < 0.001) or fat mass and fat-free mass (FFM) (+3.3%; adjusted P < 0.001)]. Further adjustment for birth weight, physical activity, and maternal educational level did not change the results (P = 0.001). The results were consistent in children and adolescents with low (P < 0.001) or high (P = 0.013) FFM, in nonoverweight (P < 0.001) or overweight (P = 0.002) children and adolescents, in offspring of nonoverweight (P < 0.001) or overweight (P = 0.003) mothers, in mothers with a low (P = 0.004) or high (P < 0.001) educational level, and in participants born within upper (P = 0.001), middle (P = 0.017), or lower (P = 0.007) tertiles of birth weight.
Conclusions: Longer exclusive breastfeeding has a beneficial effect on cardiorespiratory fitness in children and adolescents. Because early infant-feeding patterns are potentially modifiable, a better understanding of the possible programming effect of exclusive breastfeeding on cardiorespiratory fitness is of public health interest.