Physical activity, dietary protein and insulin-like growth factor 1: Cross-sectional analysis utilising UK Biobank

Abstract

Background: Insulin-like growth factor-I (IGF-1) is an anabolic hormone that stimulates cell growth and division. The effects of IGF-1 may be beneficial (muscle growth/repair) or detrimental (increased risk of several types of cancer and mortality) for health. Dietary protein and physical activity are thought to be factors that modulate IGF-1. Objective: This study analysed the relationships dietary protein vs IGF-1 and physical activity vs IGF-1 independently with a large sample size, and determined if/how physical activity affected the association between dietary protein and IGF-1 in healthy adults. Methods: Regression models were used to assess the association between dietary protein and/or physical activity on serum IGF-1 in a cross-sectional sample of 60,677 healthy adults that were enrolled in the UK Biobank project. Results: Dietary protein was positively associated with IGF-1 (0.030 nmol/L;95%CI 0.027–0.033;p < 0.001). Individuals undertaking 10–50 excess MET h/week of physical activity had 0.129 nmol/L greater IGF-1 than participants completing less than 10 excess MET h/week (95%CI 0.028–0.230). The “high” category of physical activity (>50 excess MET h/week) was not correlated with IGF-1 (−0.055 nmol/L;95%CI -0.185-0.076). When dietary protein and physical activity were included in the same model, physical activity did not change the relationship between dietary protein and IGF-1, nor visa-versa. Conclusions: The positive association between dietary protein and IGF-1 was not influenced by physical activity. The former association was stronger than the latter. Thus, when seeking to adjust IGF-1 for possible health concerns, regulating dietary protein may be more pertinent than physical activity as a primary intervention.