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Mmass edit regular amino acids6/11/2023 ![]() ![]() We previously reported that a balanced amino acid mixture stimulated muscle protein anabolism in elderly subjects and in younger adults ( 11). Hence, a nutritional supplement for the prevention or treatment of sarcopenia should stimulate muscle anabolism more efficiently than does food or common protein supplements in order to achieve the highest protein anabolic efficiency per energy unit. Thus, if the nutrient composition of the supplement is similar to that of the normal diet, it is likely that supplementation will be ineffective. This suggests that a nutritional supplement for the elderly should best be considered as more of a dietary substitute than a supplement. Second, it has been reported that elderly subjects who took supplements but did not increase their physical activity decreased their dietary intake accordingly therefore, their total daily energy intake remained unchanged ( 6). The fact that both the commercial supplements and the high-protein diet tested in elderly adults contained carbohydrate might explain the ineffectiveness of the nutritional interventions tested in the previous studies ( 6– 8). First, there is evidence that the presence of carbohydrate in a nutritional supplement for the elderly is not beneficial ( 9) and may in fact impair the anabolic response of muscle proteins to the positive effect of amino acids alone ( 10, 11). There are at least 2 possible reasons that can explain the inability of nutritional supplements or increased protein intake to enhance muscle growth and strength. However, attempts to increase muscle mass, strength, and protein synthesis with commercial nutritional supplements or high-protein diets have been unsuccessful ( 6– 8). Undernutrition has been identified as one of the contributing factors that might be prevented by increased protein or energy intakes, or both ( 3– 5). Sarcopenia is a multifactorial problem of the elderly and is characterized by muscle loss and reduced strength, which can lead to functional dependence ( 1, 2). Sarcopenia, aging, protein synthesis, proteolysis, nutritional supplements INTRODUCTION 100 mL leg volume −1) increased from the basal state ( P Results: Phenylalanine net balance (in nmol Muscle protein metabolism was measured in the basal state and during amino acid administration via l-phenylalanine infusion, femoral arterial and venous catheterization, and muscle biopsies. Objective: We assessed whether nonessential amino acids are required in a nutritional supplement to stimulate muscle protein anabolism in the elderly.ĭesign: We compared the response of muscle protein metabolism to either 18 g essential amino acids (EAA group: n = 6, age 69 ± 2 y x̄ ± SD) or 40 g balanced amino acids (18 g essential amino acids + 22 g nonessential amino acids, BAA group n = 8, age 71 ± 2 y) given orally in small boluses every 10 min for 3 h to healthy elderly volunteers. We have shown that balanced amino acids stimulate muscle protein anabolism in the elderly, but it is unknown whether all amino acids are necessary to achieve this effect. Thus, an effective supplement should stimulate muscle anabolism more efficiently than food or common protein supplements. However, if physical activity does not increase, the elderly tend to compensate for the increased energy delivered by the supplements with reduced food intake, which results in a calorie substitution rather than supplementation. ![]() Background: Nutritional supplementation may be used to treat muscle loss with aging (sarcopenia). ![]()
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