Development and application of a nutrient support to age related lean tissue mass loss in an Irish population (50-70 years); Validation of methods used to investigate cross sectional observations of the intake of nutrients implicated, and a longitudinal intervention applying a nutrient support to age related lean tissue mass loss

Prevention of the age-related loss of muscle mass and strength (sarcopaenia) is fundamental to conserving functional capability in older age and enabling independent living. To develop preventive strategies, a better understanding is needed of the lifestyle dynamics influencing age related lean tissue mass loss. Increasing evidence suggests that a modification of protein intake, which is quantitative, qualitative and optimally apportioned, is necessary to counteract progressive lean tissue loss in the elderly. Among other nutrients implicated are antioxidants. Muscle mass and strength in later life are a reflection of both the rate of muscle loss and the peak attained in early life, therefore efforts to prevent sarcopaenia also need to consider diet across the life-course and the potential effectiveness of early interventions. This thesis aimed to assess the adequacy of protein intake (quantity, quality and apportioning), and dietary total antioxidant capacity (TAC) in a convenience population of healthy, ‘young’ elderly Irish adults. This necessitated modifications to traditional, and the development of novel approaches to dietary data collection and nutrient intakes analysis methods. Two innovative nutrient intake analysis methods are proposed to estimate dietary total antioxidant capacity and protein quality (as essential amino acid content) in dietary intakes. Progressing from this assessment a subsequent aim was to investigate whether supplementing dietary intake with a milk protein rich in essential amino acids at both smaller meals in the day over a 24 week intervention, would arrest the progression of sarcopaenia in this population. The intervention study consisted of a randomised, single blind, control trial of healthy adults aged 50-70y, in which participants consumed a milk-protein based nutrient support (with >50% essential amino acid content, fortified with milk minerals and vitamin D) to age related lean tissue mass loss, or a non-nitrogenous, iso-energetic control, twice daily with smaller meals. The change in body composition, specifically whole body lean tissue mass (LTM) was the outcome assessed. At 24 weeks the mean LTM increased by 0.45 (1.06) kg in the formulation group compared to a mean decrease of 0.16 (0.88) kg in the control. Expressed as a percentage, the increase in LTM at 24 weeks was +0.91 (2.4) % in the formulation group compared to a decrease of -0.3 (2.1) % in the control group (ANOVA; F3,59= 2.616, P=0.06, 1-ß=0.861, ŋp2=0.12). The 1.2% mean difference in response between the treatment and control group was statistically significant (P=0.011). Dietary modification presents a real opportunity to prevent or delay age related losses in whole body lean tissue mass. Refinement of current methods and procedures of dietary data collection and analysis are required to comprehensively investigate correlations between nutrient intakes and sarcopaenia. Further investigation is required to assess the efficacy of single nutrient interventions as opposed to the comprehensive nutrient formulation proposed here.