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The amount of bone present at a given age is determined by the mass acquired during growth (the so-called peak bone mass) and by the subsequent rate of bone loss. The attainment of peak bone mass appears to be highly affected by the state of protein supply and intake during childhood and adolescence. Indeed, in childhood and adolescence, the need for protein is increased to meet the demand required by body growth. For instance, in animal studies, rats treated with growth hormone spontaneously select a high protein diet (1). Thus, during growth, the adaptation to lower protein intake should be much more difficult than later on in life. Protein undernutrition results in a reduction of height, weight, and overall body protein (2). The recommended daily allowance for protein varies between 2.0 in children to 1.0 in adolescents, and 0.75 g/kg per day in adults (3). On the other hand, a sufficient protein intake is also mandatory for the maintenance of bone homeostasis in the elderly. Indeed, malnutrition can be considered as a risk factor for hip fracture because it can be expected to accelerate age-dependent bone loss, to increase the propensity to fall by impairing movement coordination, to affect protective mechanisms, such as reaction time and muscle strength, and thus to reduce the energy required to fracture an osteoporotic proximal femur. |
