A six-month pilot study compared BCAA supplementation with soy protein intake to assess the effects of amino acid intake on physical (muscle) strength and mental health parameters.
BCAA was reported to improve knee muscle strength, although there was no change to skeletal mass, and was associated with reduced depressive states by stimulating production of tryptophan, a precursor to serotonin. Meanwhile, soy protein decreased serum low-density lipoprotein concentrations that led to significant improvements in muscle strength.
Writing in Nutrients, the authors comment: “Findings could be valuable for improving muscle function and managing comorbidities in elderly individuals with T2D.”
Sarcopenia is characterized by reduced skeletal muscle mass, muscle strength, and physical performance due to insufficient dietary protein. These symptoms are exacerbated in patients with T2D where up to 20% exhibit lower knee extension strength and are at risk of accelerated decline in lower muscle strength, the authors explain.
“About 30–50% of community-dwelling elderly people consumed less than the recommended amount of protein as did the elderly with diabetes. Moreover, it is difficult for elderly people to change dietary habits to achieve the recommended dietary protein intake,” they say.
Stimulating protein synthesis through BCAA supplementation is the key to improved muscle function, as demonstrated in a number of studies and therapeutic treatment, however few studies have assessed outcomes on skeletal muscle in elderly patients with T2D.
Thirty-six elderly participants (aged 65 to 80 years) with T2D were recruited from an outpatient clinic for the 24-week randomised study and assigned to either the BCAA or soy protein (comparator) group.
The BCAA group consumed an amino acid supplement containing 4g leucine, 2g valine, and 2g, isoleucine, and 36 kilocalories (kcal) of energy. The soy protein formula comprised 7.5g protein and 40kcal of energy, although the Japanese manufacturer (Meiji Co.) would not disclose the amino acid content.
Participants were required to perform aerobic exercise and ‘comprehensive’ resistance training at least three times per week, including stretching, two sets of 10 repetitions of thigh raises for each leg, and two sets of 10 squats.
A clinical research coordinator (CRC) was assigned to monitor supplement intake once a week and ensure compliance to the exercise program.
Primary outcomes considered changes in skeletal muscle mass, while secondary outcomes focused on knee muscle and grip strength, glucose metabolism, lipid metabolism, neuropsychological performance, depression and motivational states, tryptophan metabolites, renal function, and urinary albumin excretion (UAE).
Physical and mental outcomes
Participants in the BCAA group “showed a tendency” to increased knee extension muscle strength and this outcome significantly improved following soy protein intake. There was no improvement in skeletal muscle mass and no changes to glycaemic control or insulin resistance.
A notable, but unexpected finding, showed that BCAA considerably reduced knee extension muscle endurance – potentially due to decreased responsiveness of peroxisome-proliferator-activated receptor-γ coactivator-1 (PGC-1a) – despite increases in knee extension muscle strength, although there was no change in endurance with soy protein.
“That is a novel finding in terms of amino acid or protein supplementation and skeletal muscle endurance in elderly persons,” the authors’ state.
They add that “the cause of the divergent effects of BCAA or soy protein supplementation on knee extension strength and endurance remains to be elucidated”.
BCAA supplementation significantly increased serum tryptophan levels and improved depressive symptoms. The researchers postulate that supplements may have reduced serum kynurenine and kynurenine-to-tryptophan ratios, inhibited kynurenine uptake, and/or increased glutamine or glutamic acid in the brain.
Finally, supplementation with either product was deemed tolerable for the participant group demographic (elderly patients with T2D).
Study limitations include the absence of a control group, possible effects of COVID-19 on participant activity (although done was detected), non-compliance to unsupervised resistance training, and homogenous groups, that may have affected results.
Nonetheless, findings identified beneficial outcomes with amino acid supplementation on muscle strength in the elderly with T2D and demonstrated its safety in relation to insulin resistance and renal function.
‘Effects of Branched-Chain Amino Acids on Skeletal Muscle, Glycemic Control, and Neuropsychological Performance in Elderly Persons with Type 2 Diabetes Mellitus: An Exploratory Randomized Controlled Trial’
Takaaki Matsuda, Hiroaki Suzuki 1, Yoko Sugano 1, Yasuhiro Suzuki, Daisuke Yamanaka, Risa Araki, Naoya Yahagi, Motohiro Sekiya, Yasushi Kawakami, Yoshinori Osaki, Hitoshi Iwasaki, Koichi Hashimoto, Shin-Ichiro Takahashi, Yasushi Hada and Hitoshi Shimano