Effect of Reversal of the Whey protein to casein ratio of cow milk on insulin and incretin responses in humans

Rationale: Milk proteins have recognised functional properties on insulin and incretin secretion. In head-to-head comparisons, whey proteins (WP) are more efficient than casein (Cas) in hormone stimulation. Nevertheless, milk is a unique milieu, where interaction among proteins may modify their functional effects, and should not be excluded when comparing WP and Cas. Methods: We compared the effects, in young healthy volunteers, of milk loads under isolactose (3.6 g lactose x kg-1 BW) and isoproteic (0.18 g total protein x kg-1 BW) conditions. One was natural cow milk (Nat-Cow), with a Cas/WP ratio of 90/10, the other was a modified cow milk, obtained by water dilution and protein addition, to attain a WP/Cas ratio of 70/30 (High-WP milk). Blood ample were frequently taken over 4 hrs. Results: The same mild hyperglycemic response was observed. The HighWP milk exhibited a total AUC (þ z25%) and a [20’-120’] AUC (þ z45%) significantly greater (p<0.05) than those of Nat-Cow. The C-peptide response with the High-WP milk at 90’, and as the [20’-120’] AUC were greater (by þ60-80%) (p<0.05) than those of Nat-Cow milk. The [10’-90’] responses of both GLP-1 and GIP were 80-100% greater (p<0.05) with the High-WP than the Nat-Cow milk. Conclusion: Under under isolactose and isoproteic conditions, the reversal of the WP to Cas ratio in cow milk enhances insulin secretion in humans, possibly through an increased incretin response