Protein requirements of healthy pregnant women during early and late gestation are higher than current recommendations.
Level 2 - randomized trial
Individual randomized crossover metabolic study in humans.
PubMed 25527661 · doi:10.3945/jn.114.198622
What was done
Researchers determined gestational stage-specific protein requirements in 29 healthy pregnant women (aged 24-37 years) at early (11-20 weeks; n = 35 observations in 17 women) and late (31-38 weeks; n = 43 observations in 19 women; 7 participated in both) gestation. Women randomly received varying test protein intakes (0.22-2.56 g/kg/d) during study days. Diets were isocaloric (1.7 x resting energy expenditure) with crystalline amino acids based on egg protein. Protein requirements were derived using the indicator amino acid oxidation method measuring L-[1-13C]phenylalanine oxidation to 13CO2, with breakpoints determined by linear regression crossover analysis.
What was found
The estimated average requirement (EAR) for protein was 1.22 g/kg/d (R2 = 0.60; 95% CI: 0.79, 1.66 g/kg/d) in early gestation and 1.52 g/kg/d (R2 = 0.63; 95% CI: 1.28, 1.77 g/kg/d) in late gestation, exceeding the current DRI EAR recommendation of 0.88 g/kg/d.
Why it matters
Current recommendations rely on factorial calculations from nonpregnant data; this direct metabolic assessment suggests standard guidelines substantially underestimate protein needs across pregnancy stages.
Limits
The sample size was small (29 participants across 78 total study days), and the early gestation confidence interval was relatively wide. The study used acute crystalline amino acid diets rather than whole foods and did not evaluate clinical maternal or fetal outcomes.