REVIEW Protein intake and bone disorders in the elderly René Rizzoli*, Patrick Ammann, Thierry Chevalley, Jean-Philippe Bonjour Bony diseases division, centre collaborateur de l’OMS pour l’ostéoporose et les maladies osseuses, département de médecine interne, hôpital cantonal universitaire, CH 1211 Geneva 14, Switzerland (Submitted for publication February 7, 2001; accepted in revised form June 6, 2001) Summary – Malnutrition, most notably protein deficiency, contributes to the occurrence of osteoporotic fractures not only by decreasing bone mass but also by altering muscle function. Furthermore, malnutrition is associated with increased morbidity in patients with osteoporotic fractures. The somatomedin system (IGF-I) may be directly involved in the pathogenesis of osteoporotic hip fractures and their complications in elderly patients. A low IGF-I level is a risk factor for hip fracture. In subjects with appropriate intakes of vitamin D and calcium, giving protein supplements to correct an inadequate spontaneous protein intake increases circulating IGF-I levels, improves clinical outcomes after hip fracture, and prevents bone mineral density loss at the proximal femur. Supplemental protein also significantly reduces the length of inpatient rehabilitation care. These data emphasize the importance of adequate nutrient intake in the prevention and treatment of osteoporotic fractures. Joint Bone Spine 2001 ; 68 : 383-92. © 2001 Éditions scientifiques et médicales Elsevier SAS fracture / IGF-I / nutrition / osteoporosis INTRODUCTION Among the various factors that contribute to the devel- opment of osteoporosis in elderly subjects, nutritional deficiencies are clearly pivotal [1, 2]. Several nutritional deficiencies are highly prevalent among the elderly and seem particularly common in hip fracture patients [3-7]. A protein intake far below the recommended daily allowance compromises not only achievement of peak bone mass but also preservation of bone mass during aging [8, 9], as confirmed by many reports [1, 2, 10]. Furthermore, protein malnutrition may increase the risk of osteoporotic fracture by increasing the propen- sity to falls and by decreasing bone mass [11]. The increased risk of falls associated with protein malnutri- tion is ascribable to muscle weakness and to impair- ments in movement coordination and protective mechanisms such as reaction time and muscle strength. Finally, the meager protection by soft tissue in under- nourished subjects fails to cushion the bones effectively, thereby increasing the mechanical loads placed on the osteoporotic bones [5, 12-14]. PROTEIN DEFICIENCY AND OSTEOPOROTIC FRACTURE Many studies have found evidence of a link between protein intake and the metabolism of bone or of phos- phate and calcium [8, 15-22]. That too little or too much protein in the diet can adversely affect the cal- cium balance is firmly established. The higher preva- lence of hip fractures in countries where the diet is * Correspondence and reprints. E-mail address: rizzoli@cmu.unige.ch (R. Rizzoli). Joint Bone Spine 2001 ; 68 : 383-92 © 2001 Éditions scientifiques et médicales Elsevier SAS. All rights reserved S1297319X01002950/SCO