Daily pre-meal whey protein supplementation during late pregnancy significantly improved glucose profiles in women with gestational diabetes mellitus (GDM). In a randomized, double-blind, placebo-controlled trial published in Diabetologia, 62 women received either 20 g of whey protein isolate or placebo 30 minutes before breakfast throughout the third trimester.

Continuous glucose monitoring demonstrated that one-hour post-breakfast glucose was 20% lower early in the third trimester and 15% lower later in the whey protein group compared with placebo under controlled-living conditions. Under free-living conditions, glucose fell by 14% early and 8% late in pregnancy. Glycemic variability also improved, with reductions in mean amplitude of glycemic excursions (MAGE), standard deviation, and coefficient of variation, all statistically significant (p < 0.05).

Time in range (3.5–7.8 mmol/L) decreased slightly late in pregnancy during free-living monitoring (p = 0.05). These findings indicate that pre-meal whey protein effectively stabilizes glucose levels, reduces postprandial excursions, and improves glycemic variability in GDM. The authors suggest that this nutritional strategy may help delay or reduce the need for insulin therapy during pregnancy.