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Protein Requirements of Healthy Pregnant Women during Early and Late Gestation Are Higher than Current Recommendations1,2,3,4
Trina V Stephens5,6, Magdalene Payne5,6, Ronald O Ball7, Paul B Pencharz8, and Rajavel Elango5,6,9,*
+ Author Affiliations
5Child & Family Research Institute, British Columbia Children’s Hospital, Vancouver, BC, Canada;
6Department of Pediatrics, University of British Columbia, BC, Canada;
7Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada;
8The Research Institute, Hospital for Sick Children, Toronto, ON, Canada; and
9School of Population and Public Health, University of British Columbia, BC, Canada
↵*To whom correspondence should be addressed. E-mail: [email protected].
Abstract
Background: Adequate maternal dietary protein intake is necessary for healthy pregnancy. However, current protein intake recommendations for healthy pregnant women are based on factorial calculations of nitrogen balance data derived from nonpregnant adults. Thus, an estimate of protein requirements based on pregnancy-specific data is needed.
Objective: The objective was to determine protein requirements of healthy pregnant women at 11–20 (early) and 31–38 (late) wk gestation through use of the indicator amino acid oxidation method.
Methods: Twenty-nine healthy women (24–37 y) each randomly received a different test protein intake (range: 0.22–2.56 g ⋅ kg−1 ⋅ d−1) during each study day in early (n = 35) and late (n = 43) gestation; 7 women participated in both early and late gestation studies. The diets were isocaloric and provided energy at 1.7 × resting energy expenditure. Protein was given as a crystalline amino acid mixture based on egg protein composition, except phenylalanine and tyrosine, which were maintained constant across intakes. Protein requirements were determined by measuring the oxidation rate of L-[1-13C]phenylalanine to 13CO2 (F13CO2). Breath and urine samples were collected at baseline and isotopic steady state. Linear regression crossover analysis identified a breakpoint (requirement) at minimal F13CO2 in response to different protein intakes.
Results: The estimated average requirement (EAR) for protein in early and late gestation was determined to be 1.22 (R2 = 0.60; 95% CI: 0.79, 1.66 g ⋅ kg-1 ⋅ d-1) and 1.52 g ⋅ kg−1 ⋅ d−1 (R2 = 0.63; 95% CI: 1.28, 1.77 g ⋅ kg-1 ⋅ d-1), respectively.
Conclusions: These estimates are considerably higher than the EAR of 0.88 g ⋅ kg−1 ⋅ d−1 currently recommended by the Dietary Reference Intakes. To our knowledge, this study is the first to directly estimate gestational stage–specific protein requirements in healthy pregnant women and suggests that current recommendations based on factorial calculations underestimate requirements.
Trina V Stephens5,6, Magdalene Payne5,6, Ronald O Ball7, Paul B Pencharz8, and Rajavel Elango5,6,9,*
+ Author Affiliations
5Child & Family Research Institute, British Columbia Children’s Hospital, Vancouver, BC, Canada;
6Department of Pediatrics, University of British Columbia, BC, Canada;
7Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, AB, Canada;
8The Research Institute, Hospital for Sick Children, Toronto, ON, Canada; and
9School of Population and Public Health, University of British Columbia, BC, Canada
↵*To whom correspondence should be addressed. E-mail: [email protected].
Abstract
Background: Adequate maternal dietary protein intake is necessary for healthy pregnancy. However, current protein intake recommendations for healthy pregnant women are based on factorial calculations of nitrogen balance data derived from nonpregnant adults. Thus, an estimate of protein requirements based on pregnancy-specific data is needed.
Objective: The objective was to determine protein requirements of healthy pregnant women at 11–20 (early) and 31–38 (late) wk gestation through use of the indicator amino acid oxidation method.
Methods: Twenty-nine healthy women (24–37 y) each randomly received a different test protein intake (range: 0.22–2.56 g ⋅ kg−1 ⋅ d−1) during each study day in early (n = 35) and late (n = 43) gestation; 7 women participated in both early and late gestation studies. The diets were isocaloric and provided energy at 1.7 × resting energy expenditure. Protein was given as a crystalline amino acid mixture based on egg protein composition, except phenylalanine and tyrosine, which were maintained constant across intakes. Protein requirements were determined by measuring the oxidation rate of L-[1-13C]phenylalanine to 13CO2 (F13CO2). Breath and urine samples were collected at baseline and isotopic steady state. Linear regression crossover analysis identified a breakpoint (requirement) at minimal F13CO2 in response to different protein intakes.
Results: The estimated average requirement (EAR) for protein in early and late gestation was determined to be 1.22 (R2 = 0.60; 95% CI: 0.79, 1.66 g ⋅ kg-1 ⋅ d-1) and 1.52 g ⋅ kg−1 ⋅ d−1 (R2 = 0.63; 95% CI: 1.28, 1.77 g ⋅ kg-1 ⋅ d-1), respectively.
Conclusions: These estimates are considerably higher than the EAR of 0.88 g ⋅ kg−1 ⋅ d−1 currently recommended by the Dietary Reference Intakes. To our knowledge, this study is the first to directly estimate gestational stage–specific protein requirements in healthy pregnant women and suggests that current recommendations based on factorial calculations underestimate requirements.
