For eight weeks, a group of 21 Japanese men and women over the age of 65 who have suffered a stroke and have sarcopenia (or muscle tissue loss) consumed a jelly containing leucine-enriched amino acids during while in a rehabilitation program.
Twenty-three other men and women around the same age and with the same health profile that were in the program, part of a control group, did not receive the jelly.
At the end of the study, researchers found that the participants who ate the protein jelly had a significantly higher improvement in handgrip strength compared to the control group, though both groups experienced improvements over the course of the rehabilitation program.
When researchers measured the skeletal muscle mass index using bioelectrical impedance analysis, mass increase was significantly greater in the jelly group compared to participants in the control group.
“This finding suggests that this supplement, which stimulates muscle protein synthesis in older adults, counteracts muscle loss in these patients,” they wrote in their study, published online in the journal Nutrition, due for publication in the journal’s February 2019 edition.
The amino acid preparation used in the study was Amino L40, manufactured by Ajinomoto Co.
Role of leucine
Citing a 2016 study from Japan, the authors said that about half of stroke patients are malnourished, with muscle loss caused by deficient protein being one of the main problems. The outcomes of this trial provided evidence that high daily protein intake can increase the mass of the appendicular muscles.
“Both groups had a median daily intake of 1.1g/kg of body weight at baseline, and both groups had a median daily intake of 1.4 (intervention) and 1.3 (control) g/kg of body weight at the end of the study,” they wrote.
But the amino acid leucine, which the authors said has been studied for its ability to stimulate muscle protein synthesis, may help improve the action in which protein increases muscle mass and strength. Older adults are less sensitive to amino acid intake; hence, the researchers explored the effects of adding even more of it.
“Leucine is a key trigger of [post-meal] muscle protein synthesis acting via the mTOR pathway,” they wrote, referring to an intracellular signaling pathway that regulates cell cycle. “And consumption of essential amino acids enriched for leucine, as described in this trial, increases muscle protein synthesis and alleviates muscle soreness after exercise,” they argued.
“Therefore, leucine-enriched amino acid supplements appear to preserve muscle mass and physical function in older sarcopenic adults with decreased food intake.”
The sample size of the study was relatively small, it also did not include a resistance training component. “Further studies are needed to determine how the nutritional supplement improves the outcomes of stroke patients with sarcopenia in combination with other rehabilitation procedures,” they wrote.
Published online ahead of print, https://doi.org/10.1016/j.nut.2018.05.028
"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"
Authors: Yoshihiro Yoshimura, et al.