The journal Diabetologia recently published the results of a randomized and controlled clinical trial evaluating the impact of pre-meal whey protein supplementation during the 3rd trimester of pregnancy on glycemic and metabolic outcomes among women with gestational diabetes. Sixty-two women received either 20g whey isolate per day or a placebo 30 minutes before breakfast during the 3rd trimester, with lab visits and home-based measurements (both free-living and controlled conditions), in addition to continuous blood glucose monitoring.Compared to placebo, the 1-hour postprandial glucose among women receiving whey protein (controlled conditions) was 15-20% lower following breakfast, and 8-14% lower in free living conditions. Women receiving whey protein also had reduced glycemic variability, marked by a lower mean amplitude of glycemic excursions (MAGE) during both the early and late 3rd trimester.
This is not the first study to suggest a benefit of pre-meal whey protein supplementation on glycemic outcomes; the same group published a smaller, single-blind trial in Diabetes Care. The smaller trial showed a reduction in postprandial glucose levels among women with gestational diabetes as well as women with normal glucose tolerance.
An analysis of a randomized trial published in Diabetes points to a likely mechanism; using isotopically labeled glucose molecules to distinguish ingested vs synthesized glucose, this study found that among healthy young adults, whey protein (when consumed with glucose) blunted postprandial glucose excursions primarily by reducing glucose absorption. It strongly enhanced insulin and glucose-dependent insulinotropic polypeptide (GIP) production, but the net benefit was attributed to inhibition of early-phase glucose absorption. It’s not clear from these trials whether whey protein has a unique benefit, or if co-ingestion of any protein would yield the same benefits.