Leucine stimulates muscle growth without training

Supplementation with leucine results in a small increase in the muscle mass of over 65s without them having to train. Researchers at Leeds Beckett University will publish an article on this soon in the European Journal of Clinical Nutrition. The dose required for a muscle building effect is higher than the 3 g recommended generally by supplements experts.

Supplementation using a dose of at least 3g leucine, in combination with other amino acids, stimulates anabolic processes in muscle tissue. This explains why animal studies have shown that leucine supplementation prevents muscle mass from declining as a result of inactivity and why wheat-based protein has just as much anabolic effect as whey.

Most studies on the effect of leucine supplementation on muscles are molecular studies, and tell us how leucine [structural formula shown on the right] increases the activity of anabolic molecules in muscles. There have not been many studies in which researchers have looked at whether supplementation with leucine really results in more muscle in humans. For this reason alone it’s worth reason the study done by researchers at Leeds Beckett University in England.

The researchers divided 25 subjects, all healthy and aged between 65 and 75, into three groups. The first group took a placebo every day – the control group. The other two groups took capsules every day that contained a mixture of essential amino acids.

The dosage was 0.21 g amino acids/kg bodyweight per day. For someone weighing 80 kg that would amount to 16.8 g amino acids. The subjects took half the total daily dose twice a day.

One of the supplementation groups took a mix that contained 20 percent leucine. So a subject who weighed 80 kg consumed about 3.5 g leucine in the form of the supplement every day. The members of the other supplementation group took a mix that consisted of 40 percent leucine, so they consumed about 7 g leucine in supplement form each day.


Before and after the supplementation period, the researchers tested the subjects’ physical functioning. They tested the subjects’ hand grip strength, counted how many times the subjects could stand up and sit down again [30 seconds chair test] and measured how many metres the subjects could walk in 6 minutes [6 minutes walk test].

These functions improved in the subjects who had taken supplements, as the figure below shows. It was the 20 percent leucine mixture that worked best.


The mixture that contained 40 percent leucine resulted in a statistically significant increase in lean tissue mass compared with that of the placebo group. Supplementation with the mixture that contained 20 percent leucine had no effect on lean tissue mass.



The figure above compares the changes in body composition in the placebo group with those in the 40 percent leucine group.

“Long-term supplementation studies examining the effectiveness of leucine and essential amino acids enriched with leucine for prevention of either age-related sarcopenia or enhancement of lean tissue mass are few and remain equivocal”, the researchers wrote. “High-dose long-term leucine supplementation alone taken as 7.5 g of free leucine rather than as part of a mixed amino-acid mixture or meal has shown no benefit over placebo, with both groups increasing lean tissue mass by approximately 0.4 kg.”

“This contrasts with the use of leucine-enriched amino aids or the use ofa whey protein, leucine-enriched supplement, which has demonstrated beneficial acute effects on muscle protein synthesis, and particularly at higher concentrations of 40 percent.”

“Similarly, animal studies have also revealed that the amount of leucine required to maintain postprandial stimulation of protein synthesis may be higher in older animals. In our study, protein synthesis was not measured; however, we can speculate that the significant increase in lean tissue mass of subjects in the 40 percent leucine group was probably because of enhanced rates of PS as a result of an increased leucine dose (leucine intake approximately 6 g/day) and in the presence of other essential amino acids.”

Double-blind, placebo-controlled pilot trial of L-Leucine-enriched amino-acid mixtures on body composition and physical performance in men and women aged 65-75 years.


Adequate protein intake is essential to retaining muscle and maintaining physical function, especially in the elderly, and L-Leucine has received attention as an essential amino acid (EAA) that enhances protein retention. The study’s aim was to compare the efficacy of EAA mixtures on lean tissue mass (LTM) and functional performance (FP) in a healthy elderly population.

Thirty-six subjects (65-75 years) volunteered to receive capsules with EAAs (Groups A and B containing 20% and 40% L-Leucine, respectively) or placebo (lactose containing 0% L-Leucine, Group C) for 12 weeks. The daily amount ranged from 11 to 21?g (0.21?g/?kg/day) and was taken in two equal dosages alongside food, morning and evening. Main outcomes measured before and after intervention were LTM and FP (30-s arm-curl test; 30-s chair-stand test (30-CST); 6-min walk test (6-WT); and handgrip strength). Secondary outcomes included dietary intakes and physical activity.

Twenty-five subjects (11 male and 14 female) completed the study (Group A, n=8; Group B, n=8; Group C, n=9). Gains associated with medium effect sizes were noted in LTM (Group B, 1.1 ±1.1%, P=0.003) and FP (Group A in 30-CST (11.0±11.5%, P=0.02) and 6-WT (8.8±10.0%, P=0.02); Group B in 6-WT (5.8±6.6%, P=0.03) and a trend in 30-CST (13.2±16.0, P=0.06)). Significant differences between groups were not observed in secondary outcomes.

Twice-daily supplementation of EAAs containing 20% or 40% L-Leucine improved aspects of functional status and at the higher level improved LTM. Further work to establish change in a larger sample and palatable supplemental format is now required.European Journal of Clinical Nutrition advance online publication, 17 June 2015; doi:10.1038/ejcn.2015.91.

PMID: 26081485 [PubMed – as supplied by publisher]

Source: http://www.ncbi.nlm.nih.gov/pubmed/26081485

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