The effects of additional protein intake on muscle strength and physical performance in physically active elderly

Rationale: Sarcopenia is defined as the age-related loss of skeletal muscle mass, muscle strength and muscle function. These declines can lead to a decrease in physical performance, decreased independence and enhanced vulnerability, and subsequently increased health care costs. Previous studies have shown beneficial effects of enhanced protein intake in frail elderly but little is known about the effect of enhancing protein intake in currently healthy physically active elderly. It has been shown that physically active elderly have the same age-related declines in muscle strength as their inactive peers, while protein recommendations are often not met in both groups.

Objective: The present study has been designed to investigate the impact of additional protein intake on muscle strength and physical performance in physically active elderly.

Study design: The proposed intervention is a 13-week double-blind randomized placebo-controlled trial with 2 arms. The effects of daily protein supplementation (2x 15g provided at breakfast and after exercise or on days without exercise: at lunch) on muscle strength and physical performance will be investigated.

Study population: The study population includes in total 120 subjects, aged 65 years and above with a protein intake in the lowest quartile and registered to participate in the Nijmegen Four Days Marches 2017.

Intervention (if applicable): The physically active elderly subjects will be randomly assigned to the intervention or control group, receiving either protein supplementation (30 gram per day) or placebo. It will be assured that baseline protein intake, gender and age is similar between the groups. The daily supplementation consists of a protein product (30 grams of protein) or an placebo (consisting of carbohydrates). It will be given in the form of 2 drinks that need to be consumed during breakfast and after exercise (or on days without exercise, during lunch).

Main study parameters/endpoints: The primary outcomes are differences in change in muscle strength and physical performance between the intervention and control group after 12 week intervention. Changes in muscle mass and total body composition, muscle, joint and bone markers and questionnaires changes will also be assessed. Furthermore, during the Four Days Marches we will assess differences between the protein-supplemented group and the placebo group in recovery of physical performance and muscle strength and in biomarkers (inflammation, muscle, joint and bone health).

We hypothesize that the ingestion of an additional amount of dietary protein (2 x 15g per day) will increase muscle strength and physical performance in physically active elderly (≥ 65 yrs). Moreover, we hypothesize that the ingestion of additional protein in physically active elderly will have a beneficial effect on recovery of muscle and joint characteristics during the Four Days Marches.

change in maximal voluntary contraction: 2 time points

Change in SPPB: 4 time points

Protein supplements will be provided as ready-to-drink products of 250 ml containing 15
gram protein (MPC-80) and will be produced by FrieslandCampina. De placebo supplements will be provided as ready-to-drink products of 250 ml and will be produced by FrieslandCampina. The products will be vanilla flavoured. Caloric content is very similar between the products. The products will be consumed twice a day for 13 weeks.