Protein Requirements of Healthy Lactating Women Are Higher Than the Current Recommendations

Abstract

Objectives During lactation, a woman must eat an adequate amount of protein in order to maintain her own muscle mass, while also providing adequate nutrition to the infant through breast milk. The current Dietary Reference Intakes (DRI) for protein suggest, that healthy lactating women (0–6 mo postpartum) should consume an Estimated Average Requirement (EAR) of 1.05 g protein/kg/d. However, this recommendation is based on factorial calculations rather than direct experiments. Therefore, our objective was to determine the protein requirement for exclusively breastfeeding women, using the indicator amino acid oxidation (IAAO) technique. Methods Eleven healthy women (31 ± 4.1y), exclusively breastfeeding (4.7 ± 1.2 mo postpartum), were randomly assigned to receive different test protein intakes ranging from 0.29–2.41 g/kg/d divided over 40 test intakes. Participants consumed eight hourly isocaloric and isonitrogenous meals, providing energy at 1.7 x resting energy expenditure. The diets consisted of a crystalline amino acid mixture based on the composition of egg protein, except phenylalanine and tyrosine which were maintained constant across intakes. Oxidation of the tracer amino acid (L-1–13C-phenylalanine), was used to determine protein requirements by measuring F13CO2 in breath samples, collected during each study day. A breakpoint (requirement) in F13CO2 was identified by linear regression crossover analysis. Results Our preliminary results suggest that the protein requirements for exclusively breastfeeding women (3–6 mo postpartum) is ∼1.7–1.9 g/kg/d. Conclusions Our findings for dietary protein needs during lactation are higher than the current EAR of 1.05 g/kg/d recommended by the DRI, suggesting that the recommendations may be underestimated. Our results correspond well with our earlier findings of higher protein needs of 1.52 g/kg/d during late stages of pregnancy (∼36 wk gestation) determined using the IAAO method. Funding Sources Canadian Institutes of Health Research.