Dietary Aromatic Amino Acid Requirements During Early and Late Gestation in Healthy Pregnant Women

Author:

Ennis Madeleine A12ORCID,Ong Anna-Joy1,Lim Kenneth3,Ball Ronald O4,Pencharz Paul B567,Courtney-Martin Glenda56ORCID,Elango Rajavel128ORCID

Affiliation:

1. British Columbia Children's Hospital Research Institute, British Columbia Children's Hospital, Vancouver, Canada

2. Department of Pediatrics, University of British Columbia, Vancouver, Canada

3. Department of Obstetrics and Gynecology, British Columbia Women's Hospital, Vancouver, Canada

4. Department of Agricultural, Food and Nutritional Sciences, University of Alberta, Edmonton, Canada

5. Research Institute, The Hospital for Sick Children, Toronto, Canada

6. Department of Nutritional Sciences, University of Toronto, Toronto, Canada

7. Department of Pediatrics, University of Toronto, Toronto, Canada

8. School of Population and Public Health, University of British Columbia, Vancouver, Canada

Abstract

ABSTRACT Background Phenylalanine and tyrosine (referred to as total aromatic amino acids; TAAs) are essential for protein synthesis, and are precursors for important catecholamines. Current estimated average requirement (EAR) recommendations for TAA during pregnancy are 36 mg·kg−1·d−1, and has not been experimentally determined. Objectives The aim was to determine TAA requirements (dietary phenylalanine in the absence of tyrosine) during early and late gestation using the indicator amino acid oxidation (IAAO, with L-[1-13C]leucine) technique. Methods Nineteen healthy pregnant women (age 22–38 y) were studied at a range of phenylalanine intakes (5 to 100 mg·kg−1·d−1) in early (13–19 wk) and/or late (33–39 wk) pregnancy for a total of 51 study days. Graded test intakes were provided as 8 hourly isonitrogenous and isocaloric meals. Breath samples were collected for 13C enrichment analysis on an isotope ratio mass spectrometer. A plasma sample was collected and analyzed for phenylalanine and tyrosine concentrations on an amino acid analyzer. The TAA requirement in early and late pregnancy was calculated using 2-phase linear regression crossover analysis that identified breakpoints in 13CO2 production (the requirement) in response to phenylalanine intakes. Results TAA requirement during early pregnancy was 44 mg·kg−1·d−1 (95% CI: 28.3, 58.8) and during late pregnancy was 50 mg·kg−1·d−1 (95% CI: 36.1, 63.1). In early and late pregnancy, plasma phenylalanine and tyrosine concentrations rose linearly in response to graded phenylalanine intakes. Conclusions Our results suggest that the current EAR of 36 mg·kg−1·d−1 for TAAs is underestimated. When compared with results previously determined in nonpregnant adults, early pregnancy requirements were similar (43 compared with 44 mg·kg−1·d−1, respectively). During late pregnancy, a 14% higher TAA requirement was observed when compared with early pregnancy. The results from this study have potential implications for creating gestation stage-specific TAA recommendations.

Funder

Canadian Institutes of Health Research

Publisher

Oxford University Press (OUP)

Subject

Nutrition and Dietetics,Medicine (miscellaneous)

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