Dietary protein precipitation properties have effects on gastric emptying in healthy volunteers

Background & aims: Strategies that reduce the size of particles in the stomach accelerate gastric emptying. Partial dephosphorylation of casein reduces the size of protein precipitates (curds) in acid conditions and facilitates peptic digestion. We hypothesized that changing the precipitation properties of casein by partial dephosphorylation would accelerate gastric emptying. Methods: Eight healthy male volunteers entered a prospective, double blind, randomized study with crossover design. Gastric emptying of milk based formula containing either unmodified or dephosphorylated casein was assessed by scintigraphy. Gastric pH measurements were acquired concurrently. Results: A trend to faster gastric emptying was observed for the unmodified preparation, with lower median half time (unmodified 133; dephosphorylated 214 min, P=0.09) and area under the curve (unmodified 8425 min%; dephosphorylated 9135 min%, P=0.08). A positive correlation was found between half time for the dephosphorylated preparation and the treatment effect (r2=0.81, P<0.02). Gastric pH was unaffected. Conclusions: The study hypothesis was rejected; indeed gastric emptying tended to be faster for the unmodified than the dephosphorylated protein. This effect was more pronounced in subjects with slow gastric emptying on the dephosphorylated preparation. Properties other than the size of protein precipitates determine the rate of gastric emptying for milk based formula.