Human insulinotropic response to oral ingestion of native and hydrolysed whey protein.
Level 2 - randomized trial
Individual randomized controlled trial in humans
PubMed 18679613 · doi:10.1007/s00726-008-0156-0
What was done
Sixteen healthy males ingested a 500 mL solution containing 45 g of either native whey protein isolate (WPI) or whey protein hydrolysate (WPH) without carbohydrate. The study evaluated gastric emptying rate, peak plasma insulin concentration (Cmax), time to Cmax, insulin area under the curve (AUC), and circulating levels of insulinotropic amino acids.
What was found
Gastric emptying rate was not significantly altered by protein hydrolysis [18 (3) vs. 23 (3) min, n = 16; P = 0.15]. Maximum plasma insulin concentration occurred later (60 vs. 40 min) and was 28% higher after WPH compared to WPI [299 (31) vs. 234 (26) mM; P = 0.018]. The 43% increase in insulin AUC for WPH did not reach statistical significance [10.8 (2.6) vs. 7.6 (0.9) nM; P = 0.21]. Among insulinotropic amino acids, only phenylalanine reached a significantly higher peak concentration [72 (3) vs. 65 (2) microM, n = 16; P = 0.01] and a 22% increase in AUC following WPH.
Why it matters
This trial shows that hydrolysing whey protein enhances peak insulin release independent of carbohydrate co-ingestion and without altering gastric emptying speed.
Limits
The sample size was small (n = 16) and restricted solely to healthy males. The difference in overall insulin AUC was not statistically significant, and broader clinical outcomes such as postprandial glycaemia or long-term metabolic health were not reported.
Cited by
- supports Consuming large amounts of whey protein stimulates an insulin response driven by essential and branched-chain amino acids that suppresses ketosis.