Submitted to: American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/1997
Publication Date: N/A
Interpretive Summary: A woman's ability to provide her child with breast milk may be affected by balance (changes in weight/body fat.) If she loses weight, modify exercises a lot, or doesn't eat as much as she should, that could affect her milk production. Studies have shown slower growth rates of breast-fed infants of mothers in poor, rural communities from developing countries. We hypothesized that women with low body fat stores who were in negative energy balance (i.e., losing weight) would have poorer lactation performance. We studied Otomi Indian women in a rural community in Mexico who had low to moderate body mass index and measured changes in weight and body composition for 6 months after they gave birth. We measured milk production, milk composition, and their infants' growth rates. We found that energy balance did not affect milk prediction or composition, nutrient output into milk, or infant growth rates.
Technical Abstract: Lactation performance undoubtedly is a function of maternal energy balance and status. However, the threshold below which milk production is compromised has not been clearly delineated in humans. In a longitudinal study, energy balance was computed from changes in weight and body composition over 6 mo postpartum; milk production, milk composition and resultant infant growth velocities were computed at 3 and 6 mo postpartum. Twenty-one Otomi Indian women with low postpartum body mass index (BMI; 21.4+/-0.9 kg/m2) and 19 with moderate BMI (25.7+/-1.9 kg/m2) from San Mateo Capulhuac, Mexico, were studied. Body fat was determined by deuterium dilution. Milk production was estimated by 24-h test-weighing. Macronutrient content of human milk was measured by standard techniques. In both BMI groups body weight declined slightly over the 6 mo postpartum (P=0.04). In the low BMI group, but not in the moderate BMI group, body fat t(kg, %wt) decreased significantly with time (P=0.04). Energy balance (ie. changes in weight and body fat) did not affect milk production or composition, nutrient output into milk, or infant growth velocities. Milk production rates and the concentrations of protein and lactose in milk did not differ between BMI groups; fat concentration was lower in the low BMI group (P=0.04). Because of the inverse correlation between milk production and milk fat at 3 and 6 mo (r=-0.47, -0.43; P=0.01), fat output into milk did not differ between groups. Milk fat concentration was positively correlated with body fat at 3 and 6 mo (r=0.32; 0.40; P=0.04, 0.01). Infant growth velocities did not differ between groups. In conclusion, maternal energy balance of Otomi women with low (21.0 kg/m2) to moderate (25.6 kg/m2) BMI did not affect their lactation performance. Nor did negative