![]() This suggests that a nutritional supplement for the elderly should be better considered as a meal substitute rather than a true nutritional supplement. First, it has been reported that if physical activity is not increased to enhance the energy requirements, the addition of nutritional supplements to the diet of elderly subjects results in a calorie-for-calorie reduction in dietary intake so that the total daily energy intake did not change ( 11). There are 2 possible mechanisms that can explain these negative results. Yet, studies in which nutritional intervention with commercial nutritional supplements or high-protein diets were tested in elderly subjects to determine whether they could increase muscle mass and strength mostly reported negative results ( 10– 12). Several studies indicate that protein intake decreases in frail elders ( 7), and that even healthy older adults may need more protein than what was recommended by the most recent protein Dietary Recommended Intakes (DRI) for persons 55 and older ( 8, 9). Muscle anabolic response to protein and amino acid intake in aging In this article we focus on the role of nutritional intake, an anabolic stimulus, and its effects, on protein metabolism in the elderly. Additionally, taken together, these data suggest that older muscle may be more sensitive to short-term inactivity or may require different dietary intakes of nutrients to maintain a normal synthesis rate. Because most protein catabolism in daily life occurs in the basal, postabsorptive state, the results of this study suggest that sarcopenia is more likely caused by reduced stimulation or altered sensitivity to anabolic factors. ![]() In fact, we have recently reported in the largest cohort of healthy community indwelling men that, despite a decline in muscle mass, basal muscle protein synthesis and net protein balance are not reduced with healthy aging when usual diet and normal physical activity levels are not manipulated before the experiments ( 6). ![]() However, these age-related differences in muscle protein synthesis might be due to dietary manipulations and limitation of physical activity before the experiments. Previous studies suggest that sarcopenia may be due to a reduced basal rate of muscle protein synthesis ( 1– 5). Indeed, an imbalance between protein synthesis and protein breakdown rate can lead to the loss of muscle proteins. The mechanisms involved in sarcopenia have not been clearly understood. ![]() Sarcopenia is an age-related progressive loss of muscle mass that leads to muscle weakness, limited mobility, and increased susceptibility to injury. For this reason, long-term essential amino acid supplementation may be a useful tool for the prevention and treatment of sarcopenia, particularly if excess leucine is provided in the supplement.Īging, amino acids, muscle, sarcopenia, protein metabolism Recent data suggest that excess leucine may be able to overcome this age-related resistance of muscle proteins to leucine. It is likely that this stimulatory effect of essential and BCAA is due to the direct effect of leucine on the initiation of mRNA translation, which is still present in older age, although it appears to be attenuated in aged animals. ![]() Nonetheless, the older muscle is still able to respond to amino acids, mainly the essential and BCAAs, which have been shown to acutely stimulate muscle protein synthesis in older individuals. Specifically, aging is associated with changes in the muscle protein metabolism response to a meal, likely due to alterations in the response to endogenous hormones. The most recent findings regarding the role of nutritional intake on protein metabolism in the elderly will be reviewed. Although the mechanisms of sarcopenia are not clearly elucidated, age-associated alterations in the muscle anabolic response to nutritional stimuli and a decline in protein intake may be significant contributing factors. Aging is associated with a progressive loss of muscle mass (sarcopenia), which increases the risks of injury and disability. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |