Dietary Protein Intake and Anthropometric Indices of Muscle Mass in Elderly

Abstract

The etiology of the loss of muscle mass with aging is not yet fully understood but compelling evidence supports the important contribution of lifestyle in its process. Physical activity and dietary protein intake were identified as efficient means of promoting muscle hypertrophy. One of the most important prerequisite for the accretion of muscle mass is the availability of amino acids, which are ingested through diet under the form of protein. It has been demonstrated that the anabolic response to a mixed-nutrient meal is blunted with aging. However, some interventions can overact this blunted response and allow muscle accumulation. The most important parameters identified to date are the sources of protein ingested and its content in essential amino acids, especially leucine, the amount and distribution of protein intake throughout the day, physical activity as co-intervention, especially resistance training, and the timing of ingestion with resistance training. According to the current knowledge, animal sources of protein are more likely to enhance muscle mass accretion than vegetable source of protein. Among essential amino acids, leucine is a key regulator of protein synthesis. The distribution of a sufficient amount of protein throughout three meals during the day (30 g/meal), as opposed to a large amount in one meal, is preferred. When resistance training and protein intake are combined, the most efficient timing for the ingestion is immediately (or within 2 h) after training. The stimulus of protein intake and physical activity promote protein synthesis and inhibit protein breakdown. In the long term, a positive balance between protein synthesis and breakdown would have significant impact on muscle mass, strength, physical capacity and quality of life.