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Scherbinsky, Kerri

University of British Columbia

Background: Pregnancy places a unique stress on maternal metabolism and requires an increased dietary consumption of many nutrients, such as protein and amino acids. Methionine is an indispensable amino acid- one which can only be obtained from the diet. Cysteine is a conditionally indispensable amino acid, only needed from dietary sources when there is not adequate methionine present in the diet. Currently, dietary recommendations for these two amino acids (total sulfur amino acids; TSAA), are based on factorial estimates from work on adult men. Additionally, ensuring plant-based protein sources (where methionine is known to be first limiting) can meet these dietary protein recommendations in a pregnant population is of importance. Objectives: (1) Determine dietary TSAA and (2) minimum methionine requirements during early and late-stage pregnancy, in the absence of dietary cysteine and presence of excess dietary cysteine, respectively. (3) Determine the influence of plant-based food sources (soy and pea protein isolate) on protein synthesis. Methods: Using the indicator amino acid oxidation method, (1) healthy pregnant females (n= 25) were studied in early or late pregnancy using graded dietary intakes of methionine in the absence of dietary cysteine for a total of 70 study days, (2) healthy pregnant females (n=23) were studied in using graded dietary intakes of methionine in the presence of excess dietary cysteine (25 mg/kg⁻¹/day⁻¹), for a total of 61 study days and, (3) healthy pregnant (late gestation, n=6) and non-pregnant (n=8) were studied using different protein sources (pea, soy, L-amino acids, and control). Results: (1) The TSAA requirements were determined to be 11.1 and 15.0 mg/kg⁻¹/day⁻¹ in early and late pregnancy, respectively. (2) The minimum methionine requirements were determined to be 7.9 and 9.1 mg/kg⁻¹/day⁻¹ in early and late pregnancy, respectively. (3) No consistent difference in protein synthesis was seen between test protein sources. Conclusion: TSAA and minimum methionine requirements have been directly determined in a healthy pregnant population. TSAA requirements seem to be 25-45% lower than current recommendations of 20 mg/kg⁻¹/day⁻¹, while minimum methionine requirements are considerably high. Protein synthesis during pregnancy is not different when tested using protein isolates, which are lower in methionine content.

Text

2024-08-01

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/88831

Reproductive and Developmental Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/