The Effect of Milk and Meat on IGFs in Prepubertal Boys

The objective of the study is to examine whether a high protein intake (PI) from either milk or meat, at a level often seen in late infancy, in healthy, prepubertal children can increase fasting levels of serum IGF-I, IGFBP-3 and IGF-I/IGFBP-3 as well as insulin, glucose and HOMA insulin reststance, HOMA beta cell function and amino acids.

IGF-I levels are positively associated with growth velocity in children and some studies suggest that a high animal PI can stimulate growth. During protein deprivation IGF-I decrease, but it is unknown whether a high PI can increase s-IGF-I in well-nourished children.

Insulin is also a growth factor, and studies have found that postprandially, milk possess some insulinotrophic effect not related to its carbohydrate content. However, the effect on fasting insulin in children is unknown.

Design: Twenty-four 8-y-old boys are asked to take either 1.5 l of skimmed milk (n=12) or the same amount of protein as 250 g low fat meat (n=12) daily for seven days. The remaining diet they can choose freely. At baseline and after seven days, anthropometrical variables are measured, diet is registered (3-d weighed records), and the blood analytes are determined after fast.

Inclusion criteria

• habital milk intake more than 500 mL/d
• willing to increase intake of milk or meat considerably for one week

Exclusion criteria

• chronic illnesses
• children who suffer from any condition likely to affect their protein metabolism or growth