Milk consumption and the prepubertal somatotropic axis

Abstract

Background: Nutrients, hormones and growth factors in dairy foods may stimulate growth hormone (GH), insulin-like growth factor I (IGF-I), and raise the ratio of IGF-I to its binding protein, IGFBP-3. We conducted pilot studies in Mongolia and Massachusetts to test the extent to which milk intake raised somatotropic hormone concentrations in prepubertal children.

Methods: In Ulaanbaatar, we compared plasma levels before and after introducing 710 ml daily whole milk for a month among 46 10-11 year old schoolchildren. In a randomized cross-over study in Boston, we compared plasma hormone levels of 28 6-8 year old girls after one week of drinking 710 ml low fat (2%) milk with their hormone levels after one week of consuming a macronutrient substitute for milk.

Results: After a month of drinking whole milk, Mongolian children had higher mean plasma levels of IGF-I (p < 0.0001), IGF-I/IGFBP-3 (p < 0.0001), and 75th percentile of GH levels (p = 0.005). After a week of drinking low fat milk, Boston girls had small and non-significant increases in IGF-1, IGF-1/IGFBP-3 and GH.

Conclusion: Milk drinking may cause increases in somatotropic hormone levels of prepubertal girls and boys. The finding that milk intake may raise GH levels is novel, and suggests that nutrients or bioactive factors in milk may stimulate endogenous GH production.

Figure 1

Distributions of plasma somatotropic hormones in two pilot studies. The Mongolia study compared concentrations of growth hormone (GH) (1a), insulin-like growth factor I (IGF-I) (1b), and the ratio of IGF-I to its binding protein 3 (IGF-I/IGFBP-3) (1c) among 9–11 year old Mongolian boys and girls (n = 46) before (red line) and after (blue line) one month of drinking 710 ml whole milk daily. The Boston study included 6–8 year old girls (n = 28) whose concentrations of GH (1d), IGF-I (1e), and the ratio of IGF-I/IGFBP-3 (1f) were measured after 1 week consuming 710 ml of lowfat milk daily (blue line) and one week of consuming a vegetable-based macronutrient substitute for milk (red line). a) Mongolian GH. b) Boston GH. c) Mongolian IGF-I. d) Boston IGF-I. e) Mongolian IGF-I/IGFBP-3. f) Boston IGF-I/IGFBP-3.