Why Leucine Makes Sense for Seniors

As we grow older, age-related loss of muscle mass, or sarcopenia, is unavoidable. Fortunately, we can modify the rate and degree at which sarcopenia occurs with simple nutritional and lifestyle interventions.

Unquestionably, muscle strength and function is deeply associated with quality of life in senior citizens. Hand grip strength alone—not to mention arm, leg and core body strength—is a meaningful clinical predictor of quality of life in older adults. Healthy muscles support one’s ability to balance (avoid falls), perform activities of daily living with ease (maintain independence), engage in pleasurable outdoor activities, participate in athletics and so on.

From the time our patients reach middle age, it is our duty and honor as practitioners to educate them on the value of optimizing muscle physiology, and to provide strategies for maintaining and even increasing muscle mass when losses have occurred. For this purpose, the branched chain amino acid leucine can offer significant benefits.

It has been suggested that of all amino acids, leucine plays the major role in regulating metabolic function. Independent of insulin, it is capable of inhibiting muscle protein breakdown and of stimulating muscle protein synthesis—the exact two mechanisms required for counteracting sarcopenic muscle wasting.

Animal research has clearly shown that in aging muscle, normal postprandial levels of leucine are inadequate to stimulate muscle protein synthesis; however, muscle protein synthesis resumes in the presence of significantly increased leucine concentrations. Such findings suggest a role for supplementation with this readily available, cost-effective amino acid.

Numerous studies have examined the effect of leucine supplementation on sarcopenia in humans by measuring various parameters such as handgrip strength, body composition, and appendicular skeletal muscle (ASM), a term referring to all the muscles found in the upper back, shoulders, arms, legs, and pelvic girdle collectively. Assessment of ASM is an important tool for diagnosing geriatric syndromes associated with skeletal muscle wasting.

One randomized controlled trial, published in the journal Nutrition in 2019, gave either an amino acid supplement enriched with high levels of leucine or a placebo to 44 older (age 65+) post-stroke patients with sarcopenia. Muscle mass, muscle strength and physical function were assessed before and after the intervention. Along with taking either the supplement or placebo, patients in both groups performed low-intensity resistance training and participated in a post-stroke rehabilitation program.

The supplement was taken once daily, contained 3 grams of leucine along with other amino acids, and was consumed within 30 minutes following performance of a sit-to-stand exercise.

After eight weeks, it was observed that handgrip strength and Functional Independence Measure improved in both groups, but gains were significantly greater in leucine-supplemented subjects. With regards to appendicular skeletal muscle, only those in the leucine treatment group experienced a significant increase.

An earlier meta-analysis of randomized controlled trials published in the British Journal of Nutrition examined the effectiveness of leucine supplementation on muscle protein synthesis and body composition in elderly patients. After conducting a thorough review of literature available on Medline, Cochrane, EMBASE and Google Scholar sites, the authors of this paper concluded that compared to control groups, the rate of muscle protein synthesis is significantly increased in leucine supplemented seniors.

By Diana Allen, MS, CNS, Product Development Manager

Moss Nutrition Digest #33 – 08/2022 – PDF Version

REFERENCES

1. Dardavet D, Rieu I, et al. Leucine: a key amino acid in ageing-associated sarcopenia? Nutr Res Rev. 2003 Jun;16(1):61-70.

2. Yoshimura Y, Bise T, et al. Effects of a leucine-enriched amino acid supplement on muscle mass, muscle strength, and physical function in post-stroke patients with sarcopenia: A randomized controlled trial. Nutrition. 2019 Feb;58:1-6.

3. Xu Z, Tan Z, et al. The effectiveness of leucine on muscle protein synthesis, lean body mass and leg lean mass accretion in older people: a systematic review and meta-analysis. Br J Nutr. 2015 Jan 14;113(1):25-34.