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CHAPTER 5 Nutrition, Protein Turnover and Muscle Mass
Stéphane Walrand1, Christelle Guillet2 and Yves Boirie1
1 Université Clermont Auvergne, CHU Clermont-Ferrand, INRAE, UNH, F-63000 Clermont—Ferrand, France
2 Université Clermont Auvergne, INRAE, UNH, F-63000 Clermont—Ferrand, France
INTRODUCTION
Muscle erosion, which begins after the age of 50 years, is one of the most important factors of disability in older people, but it may also occur early in life in case of chronic disease [1]. The cumulative decline in muscle mass reaches 40% from 20 to 80 years. The magnitude of this phenomenon as a public health problem is now well established as there has been a lot of epidemiological studies and meta‐analysis focusing on the decrements of strength and muscle mass with advancing age. So, sarcopenia has been recognized as a specific disease with an International Classification of Diseases (ICD) code (M62.84) [2]. The reduction in muscle mass and strength provokes an impaired mobility and increased risk for falls and fall‐related fractures. In addition, muscle loss is associated with a decrease in overall physical activity levels with subsequent metabolic alterations such as obesity, insulin resistance, and a reduction in bone density in older persons. Sedentary individuals, subjects with poor protein intakes, low vitamin D and low testosterone levels, and those suffering from debilitating or inflammatory diseases are at greater risks of sarcopenia. As older person population increases around the world, the involuntary loss of muscle mass with aging