Dietary strategies to augment muscle mass in the elderly

Background: The world population is aging rapidly. This growth of the aging population is accompanied by an increased number of frail elderly people who are at risk of adverse health outcomes such as disability, co-morbidity and mortality. A dominant feature of frailty is the age related loss of muscle mass, strength and performance, also called sarcopenia. Resistance-type exercise training and dietary protein supplementation are considered promising strategies to reverse sarcopenia and subsequent frailty. However, strong evidence for the impact of protein supplementation with or without resistance exercise in frail elderly people is scarce. Well-designed intervention studies in frail elderly people are needed to define new leads for the development of nutritional and exercise interventions to effectively prevent or treat the progressive loss of muscle mass, strength and physical performance with aging. Therefore, the aims of this thesis are to study 1) the impact of protein supplementation and 2) the impact of protein supplementation during prolonged resistance-type exercise training on muscle mass, strength and physical performance in frail elderly people.

Methods: First, we studied various characteristics of dietary protein intake, including the distribution of dietary protein intake throughout the day, and the use of protein-containing food sources in various elderly populations. With this knowledge, we designed two large intervention trials to study the impact of dietary protein supplementation with or without prolonged resistance-type exercise training on muscle mass, strength and physical performance in frail elderly people. In addition, we assessed the usefulness of handgrip strength as a measure of post exercise strength differences and studied the association of vitamin D status and vitamin D intake on muscle mass, strength and physical performance in a frail elderly population.

Results: Dietary protein intake in frail and institutionalized elderly people were especially low at breakfast and lunch. Supplementing protein at breakfast and lunch did not increase muscle mass but improved physical performance in frail elderly people. Resistance-type exercise training improved muscle leg strength and physical performance, but not handgrip strength. Supplementing protein at breakfast and lunch was required to significantly increase muscle mass during prolonged resistance-type exercise training in frail elderly people. Furthermore, low vitamin D status and vitamin D intake were associated with impaired physical performance.

Conclusions: Although dietary protein supplementation does not increase muscle mass, it represents a promising strategy to improve physical performance in frail elderly people. Prolonged resistance-type exercise training represents an effective strategy to improve strength and physical performance, but dietary protein supplementation is required to allow muscle mass gain during exercise training in frail elderly people.