Dietary Aromatic Amino Acid Requirements During Early and Late Gestation in Healthy Pregnant Women. Issue 12 (13th November 2020)

• Record Type: Journal Article
• Authors: Ennis, Madeleine A; Ong, Anna-Joy; Lim, Kenneth; Ball, Ronald O; Pencharz, Paul B; Courtney-Martin, Glenda; Elango, Rajavel
• Is Part Of: Journal of nutrition. Volume 150:Issue 12(2020)
• Page Start: 3224
• Page End: 3230
• Publication Date: 2020-11-13
• Subjects: stable isotopes -- phenylalanine -- tyrosine -- pregnancy -- amino acid requirements -- indicator amino acid oxidation; Nutrition -- Periodicals; Diet -- Periodicals; 613.205
• DOI: 10.1093/jn/nxaa317
• Languages: English
• ISSNs: 0022-3166

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- 13 C]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 13 C 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 13 CO2 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.