Total sulfur amino acid requirements are higher during late gestation compared with early gestation in healthy Canadian pregnancies in a repeated-measures trial.

BACKGROUND

Dietary Reference Intake (DRI) Recommendations for total sulfur amino acids (TSAAs; methionine + cysteine) during pregnancy are based on factorial calculations using data from adult males. To date, no data exist on TSAA requirements obtained directly during pregnancy.

OBJECTIVES

The objective of this study was to examine whether TSAA requirements during early (11-20 wk) and late (31-40 wk) gestation in healthy females with singleton pregnancies are different than current recommendations, and different between early and late gestation using the indicator amino acid oxidation (IAAO) technique.

METHODS

Twenty-five females 20-40 y with a healthy singleton pregnancy were studied using the IAAO technique in a repeated measures design for a total of 70, 8-h d. On each study day a methionine test intake (range: 0-40 mg⋅kg⋅d) was provided in 8 hourly, isonitrogenous and isocaloric meals with cysteine excluded from the diet. Breath samples were collected at baseline and isotopic steady state of orally provided L-1-C-Phenylalanine for measurement of phenylalanine oxidation. The requirement was determined using biphasic linear regression crossover analysis to identify a breakpoint in CO production, representing the estimated average requirement (EAR).

RESULTS

The TSAA requirement in healthy pregnant participants in early gestation was 11.1 mg⋅kg⋅d {R = 0.79, R = 0.79; 95% confidence interval [CI] (8.9, 13.3 mg⋅kg⋅d)} and 15.0 mg⋅kg⋅d (R = 0.72, R = 0.79; 95% CI [13.0, 17.0 mg⋅kg⋅d]) in late gestation. The difference between confidence intervals of the 2 breakpoints was = -3.9 ± 3.0, and statistically different.

CONCLUSIONS

We directly measured TSAA requirements in healthy pregnant mothers, and our findings suggest that requirements are lower than current DRI recommendations of 20 and 25 mg⋅kg⋅d, as the EAR, and Recommended Dietary Allowance, respectively. Late gestation TSAA needs are significantly different and increased 35% compared with early gestation. Recommendations for TSAA intake need to be tailored for gestational stage. This clinical trial was registered at clinicaltrials.gov as NCT04326322.