The nutrition for healthy living study: A randomised clinical trial assessing the effect of protein sources on healthy ageing

BACKGROUND: Worldwide, populations are ageing with significant impact on health patterns. Studies have shown that low protein, high carbohydrate diets are associated with more favourable outcomes. Plant-based diets have also been shown to have a positive impact on cardiometabolic health, weight loss and prevention of all causes of mortality. OBJECTIVE: The aim of the current study is to assess the main and interactive effects of two macronutrient interventions in a 2 × 2 factorial dietary design to determine their effects on appetite and health outcomes in older individuals. METHODS: Individuals aged 65 to 75 with a BMI between 20 and 35 kg/m2 were recruited. Participants were provided with ad libitum access to one of four diets for four weeks, designed as a 2 × 2 factorial. Each dietary treatment provided 14% of energy as protein, which was either omnivorous or semi-vegetarian in origin. The remaining complement of macronutrient energy (80–82%) was either relatively high in fat (37–41% of energy) and low in carbohydrates (41–43%), or vice versa (28–29% fat with 53% carbohydrate). Study diets were provided via a meal delivery company. Self-completed questionnaires, biospecimen and clinical assessments were collected before and after intervention to assess cardio-metabolic, oral and gut health, body composition and physical performance. RESULTS: Trial status is currently ongoing (sample and data analyses). CONCLUSIONS: This study will help determine whether protein-source (plant vs animal) and fat to carbohydrate ratio have an impact on predictors of healthy ageing. These findings will also create a sound foundation on which to base nutritional interventions in older individuals to support healthy ageing.