Animal protein intake, serum insulin-like growth factor I, and growth in healthy 2.5-y-old Danish children.

Studies from developing countries indicate that intake of animal protein, especially of milk, is associated with greater velocity of linear growth in childhood. Whether the same association exists in industrialized countries, where protein intake is high, has not yet been established. In this study, associations between protein intake, serum insulin-like growth factor I (sIGF-I) concn., and height in healthy children were analysed. Diet (7-day record) and sIGF-I (radioimmunoassay) data were available from 90 children (54 boys). The 10th, 50th and 90th percentiles of protein intake were 2.4, 2.9 and 4 g/kg/day, respectively; 63% was animal protein. In multiple linear regressions with adjustment for sex and wt., height (cm) was positively associated with intakes of animal protein (g/day; P = 0.01) and milk (P = 0.007), but not with those of vegetable protein or meat. The sIGF-I concn. was significantly associated with intakes of animal protein (P = 0.01) and milk (P = 0.045), but not with those of vegetable protein or meat. sIGF-I concn. were positively associated with height (P = 0.02). It is concluded that milk intake is positively associated with sIGF-I concn. and height. Increases in milk intake from 200 to 600 ml/day corresponded to a 30% increase in circulating IGF-I. Results suggest that milk compounds have a stimulating effect on sIGF-I concn. and, thereby, on growth.