Is Leucine The Key to Retaining Aging Muscle?

During adulthood we are in a fight to maintain or increase muscle mass. Does Leucine supplementation help?

Most of us want to live a long time. But there is a difference between just being alive and living. Being vibrant in our later years is a function of many moving parts coming together. Things like genetics, avoidance of risky behaviors, diet, exercise, and happiness all play a role. The one thing that is for sure is that if we lose enough muscle mass our activities and independence will decline rapidly.

Science Weighs in on Leucine

Research has been done to study the retention of muscle mass in older adults. It’s important for older adults to be above the current RDA requirements of 0.8g/kg/day, and the type of protein consumed is important as well.

A current study looked at the intake of leucine in 20 men aged between 65 and 85. Leucine is a primary regulator of muscle anabolism, or in other words, you need leucine to help build muscle. The study was of short duration, just five days, but included specific data from muscle biopsies obtained from the participants to measure protein synthesis in the muscle.

The researchers had the men consume a RDA protein diet of 0.8g/kg/day, and some of the men consumed a higher protein diet of 1.2g/kg/day. For the first two days each group took a placebo in place of leucine supplementation. For the last three days the men took a leucine supplementation. The amount of leucine was 5g per meal. A bout of resistance training was done during placebo timeframe as well as during the leucine supplementation.

As we age, our protein requirements go up. 

The results did show an increase in protein synthesis in the muscles tested with leucine supplementation as compared to placebo. The results were similar for the RDA protein group and the higher protein group. Resistance training in both situations increased protein synthesis.

Leucine supplementation of 5g at each meal did improve muscle protein synthesis compared to not having leucine, albeit not a huge effect. When resistance training was added, both leucine and placebo groups did have relatively higher protein synthesis. The leucine group increased muscle building regardless of whether the diet was the RDA protein guidelines or higher.

Look at the Bigger Picture

Every study is just a piece of a puzzle. They are only part of the bigger picture because as we age, our protein requirements go up. During adulthood we must fight to maintain or increase muscle mass. Instead of 0.8g/kg/day of protein, aim for 1.5g/kg/day if you are an older adult or are an active younger adult. Plug a few days of your diet into a nutrient database and assess where you are. Resistance training is absolutely vital to help stimulate muscle growth and help use the protein you are ingesting.

Regarding leucine, supplementation may be a viable option if your muscle mass is suffering and resistance training and protein intake alone are not helping. However, it may be helpful to know which foods are higher in leucine, so you can try these food sources first:

  • Chicken
  • Soy tempeh
  • Beef
  • Pork
  • Cheese
  • Nuts
  • Peanuts
  • Fish and shellfish
  • Beans

Protein and Training Are Key

It is possible that perhaps a decline in muscle as we age can be mediated by a prescription to your local sushi restaurant instead of a cocktail of medications. Of course every situation is different, but at some level we all must do resistance training and eat high quality protein.

Feel better as you age:

Facing the Second Half of Your Fitness Life


1. Landi, Francesco, Riccardo Calvani, Matteo Tosato, Anna Martone, Elena Ortolani, Giulia Savera, Emanuela D’Angelo, Alex Sisto, and Emanuele Marzetti. “Protein Intake and Muscle Health in Old Age: From Biological Plausibility to Clinical Evidence“. Nutrients 8, no. 5 (2016): 295. doi:10.3390/nu8050295.

2. Murphy, C. H., N. I. Saddler, M. C. Devries, C. Mcglory, S. K. Baker, and S. M. Phillips. “Leucine Supplementation Enhances Integrative Myofibrillar Protein Synthesis in Free-living Older Men Consuming Lower- and Higher-protein Diets: A Parallel-group Crossover Study“. American Journal of Clinical Nutrition 104, no. 6 (2016): 1594-606. doi:10.3945/ajcn.116.136424.

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