Original Article

European Journal of Clinical Nutrition (2009) 63, 1076–1083; doi:10.1038/ejcn.2009.34; published online 27 May 2009

Differential effects of casein versus whey on fasting plasma levels of insulin, IGF-1 and IGF-1/IGFBP-3: results from a randomized 7-day supplementation study in prepubertal boys

C Hoppe1,2, C Mølgaard1, C Dalum1, A Vaag3 and K F Michaelsen1

  1. 1Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark
  2. 2Department of Nutrition, National Food Institute, Technical University of Denmark, Søborg, Denmark
  3. 3Steno Diabetes Centre, Gentofte, Denmark

Correspondence: Dr C Hoppe, Department of Nutrition, National Food Institute, Technical University of Denmark, Mørkhøj Bygade 19, DK-2860 Søborg, Denmark. E-mail: cahop@food.dtu.dk

Received 26 June 2008; Revised 20 March 2009; Accepted 15 April 2009; Published online 27 May 2009.

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Abstract

Background/Objectives:

 

Milk increases both fasting insulin and insulin-like growth factor 1 (IGF-1), and thereby growth, in healthy prepubertal boys. It is, however, unknown which components in milk are responsible for milk's growth-stimulating effect.

Subjects/Methods:

 

To get closer to the identification of which components in milk that stimulate growth, we have performed an intervention study with 57 eight-year-old boys in which we examined the effects of the two major milk protein fractions, whey and casein, and milk minerals (Ca and P) in a 2 × 2 factorial design on IGFs and glucose–insulin metabolism. The amounts of whey and casein were identical to the content in 1.5l skim milk. The amounts of Ca and P were similar to 1.5l skim milk in the high-mineral drinks, whereas the amounts of Ca and P were reduced in the low-mineral drinks.

Results:

 

There were no interactions between milk mineral groups (high, low) and milk protein groups (whey, casein). Serum IGF-1 increased by 15% (P<0.0001), whereas there was no change in fasting insulin (P=0.36) in the casein group. In the whey group, fasting insulin increased by 21% (P=0.006), with no change in IGF-1 (P=0.27). There were no independent effects of a high milk mineral intake on IGF-1 and insulin.

Conclusions:

 

The main milk protein fractions exhibit important but different growth-promoting effects by increasing either fasting insulin (whey) or IGF-1 (casein) levels.

Keywords:

milk, casein, whey, IGF-1, insulin, children

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