Protein intake and bone health

Abstract

In the development and maintenance of bone structures resistant to usual mechanical stresses, adequate nutrition plays an important part. In addition to calcium associated with an adequate supply of vitamin D, dietary protein represents a key nutrient for bone health and thereby for the prevention of osteoporosis. During growth, protein under nutrition from infancy to childhood and adolescence results in reduced bone mass and strength, thereby increasing the risk of fragility fracture in later life. On the contrary, high protein intake, particularly when associated with physical activity, favors healthy development and peak bone mass acquisition, thereby enabling individuals to reach their genetic potential. There is a positive interaction between dietary protein, calcium-phosphate economy, and bone metabolism. This interaction appears to be mediated by the anabolic bone trophic factor IGF-I, the hepatic production of which is stimulated by amino acids supplied by dietary proteins. Amino acids such as arginine can exert a direct positive effect on the IGF-I production by bone forming cells. In young adulthood energy deficit, as observed in anorexia nervosa, can be associated with insufficient protein supply, low circulating IGF-I, bone loss and increased risk of fragility fracture. With aging, the reduction in the protein intake is associated in both genders with a decrease in the serum level of IGF-I, lower femoral neck aBMD, and poor physical performance. Protein under nutrition is often present in patients experiencing hip fracture. Furthermore, clinical outcome after hip fracture can be significantly improved by normalizing protein intake, which is associated with a rise in the serum IGF-I level. Thus, dietary protein contributes to bone health from early childhood to old age. An adequate intake of proteins should be recommended in the prevention and treatment of postmenopausal and age-dependent osteoporosis.