The study investigated the effects of high protein intake on growth and Insulin-like Growth Factor (IGF-I) from 9 to 12 months of age. 83 healthy infants received either whole milk (WM) or infant formula and fish oil or no fish oil (2 x 2 design). Intake of WM significantly increased the protein energy percentage (PE%), whereas there was no effect on size. The milk intervention increased IGF-I in boys but not in girls. Intake of fish oil had no effect on the outcomes. There was a significant correlation between weight and IGF-I at 12 months. PE% was positively associated with IGF-I after adjusting for sex and breastfeeding at both 9 and 12 months. The study concludes that results are consistent with the hypothesis that high milk intake stimulates growth.