Whey is Insulinotropic

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Glycemia and insulinemia in healthy subjects after lactose-equivalent

meals of milk and other food proteins: the role of plasma amino acids

and incretins1,2,3

Mikael Nilsson, nne Stenberg, Anders H Frid, Jens J Holst and

Inger ME Björck

1 From the Department of Applied Nutrition and Food Chemistry, Lund

University, Sweden (MN, MS, and IMEB); the Clinic of Endocrinology,

University Hospital MAS, Malmö, Sweden (AHF); and the Department of

Medical Physiology, The Panum Institute, University of Copenhagen,

Denmark (JJH)

Background: Milk products deviate from other carbohydrate-containing

foods in that they produce high insulin responses, despite their low

GI. The insulinotropic mechanism of milk has not been elucidated.

Objective: The objective was to evaluate the effect of common dietary

sources of animal or vegetable proteins on concentrations of

postprandial blood glucose, insulin, amino acids, and incretin

hormones [glucose-dependent insulinotropic polypeptide (GIP) and

glucagon-like peptide 1] in healthy subjects.

Design: Twelve healthy volunteers were served test meals consisting

of reconstituted milk, cheese, whey, cod, and wheat gluten with

equivalent amounts of lactose. An equicarbohydrate load of white-

wheat bread was used as a reference meal.

Results: A correlation was found between postprandial insulin

responses and early increments in plasma amino acids; the strongest

correlations were seen for leucine, valine, lysine, and isoleucine. A

correlation was also obtained between responses of insulin and GIP

concentrations. Reconstituted milk powder and whey had substantially

lower postprandial glucose areas under the curve (AUCs) than did the

bread reference (–62% and –57%, respectively). Whey meal was

accompanied by higher AUCs for insulin (90%) and GIP (54%).

Conclusions: It can be concluded that food proteins differ in their

capacity to stimulate insulin release, possibly by differently

affecting the early release of incretin hormones and insulinotropic

amino acids. Milk proteins have insulinotropic properties; the whey

fraction contains the predominating insulin secretagogue.

Key Words: Glycemic index • insulin index • milk • whey • food

proteins • insulinotropic amino acids • amino acids • incretin

hormones