The aim of the present paper is to critically review the details of the published nutrition intervention trials, with and without exercise, targeting
sarcopenia.
Sarcopenia is the loss of muscle mass, strength and/or performance with age. Since
amino acids and energy are required for muscle synthesis it is possible that nutritional intake influences
sarcopenia. Nutritional studies are challenging to carry out because of the complexity of modulating dietary intake. It is very difficult to change one nutrient without influencing many others, which means that many of the published studies are problematic to interpret. The studies included evaluate whole
protein,
essential amino acids and β-
hydroxyl β-methylbutyrate (HMB). Whole-
protein supplementation failed to show a consistent effect on muscle mass, strength or function. This can be explained by the variations in study design, composition of the
protein supplement and the failure to monitor voluntary food intake, adherence and baseline nutritional status.
Essential amino-acid supplements showed an inconsistent effect but there are only two trials that have significant differences in methodology and the supplement used. The HMB studies are suggestive of a beneficial effect on older adults, but larger well-controlled studies are required that measure outcomes relevant to
sarcopenia, ideally in sarcopenic populations. The issues of timing and distribution of
protein intake, and increased splanchnic
amino-acid sequestration are discussed, and recommendations for future trials are made.