Leucine Supplements Enhance Protein Synthesis in Older Men

Sarcopenia (the progressive loss of muscle mass) is very common in old age and can contribute to disability and mortality. In the elderly, muscle protein synthesis is often reduced, with a small to moderate protein intake potentially being a contributing factor. Studies have shown that leucine supplementation can be an important factor for this synthesis, but long-term trials had not been able to demonstrate its effectiveness.

A research group from McMaster University recently published their findings in the American Journal of Clinical Nutrition. They investigated whether leucine supplementation had an effect on muscle protein synthesis. Twenty healthy, non-vegetarian, older men (65 to 85 years old) were included in the study between April and July 2015. The first group consumed a low-protein (LP) diet, while the second consumed a high-protein (HP) diet. During the first two days, participants in both groups consumed placebo supplements with their diet, whereas during days 3 to 5, they received leucine supplements. Participants performed a unilateral leg extension exercise on day 0 and day 3, and muscle biopsies were obtained on days 0, 3, and 6. On day 0, participants consumed an isotope to mark newly synthesized muscle cells. Blood samples were also collected throughout days 2 and 5.

There was no change in body mass during the study. Neither diet had an effect on glucose metabolism. Blood leucine levels were higher with its supplementation than with placebo. Additionally, muscle protein synthesis was higher after leucine supplementation than placebo, and did not differ between the LP and HP diet groups. Also, synthesis was higher in the exercised leg than in the non-exercised leg after both placebo and leucine treatment.

In conclusion, this was the first study to show the beneficial short-term effect of leucine supplementation on muscle protein synthesis in older men. Additional research is needed to show whether these effects are maintained long-term, but if so, leucine supplementation could become a simple dietary strategy to prevent muscle mass loss in older adults.

Source: https://www.medicalnewsbulletin.com/leucine-supplements-enhance-protein-synthesis-older-men/

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