Beyond gut health: The effects of probiotics on muscle mass and strength in older adults Original paper

In this meta-analysis of randomized controlled trials, consuming probiotic-fortified products or supplemental probiotics improved muscle mass and strength among older adults. However, there was substantial variation between the studies, which decreases our confidence in the results.

The effect of probiotics and probiotic-fortified products on muscle mass and muscle strength (markers of sarcopenia) in older adults.

A total of 733 older adults from China, Italy, Sweden, Japan, Taiwan, Thailand, and the United Arab Emirates, some of whom had frailty and sarcopenia.

The average age and the percentages of men and women were not reported.

A meta-analysis of 7 randomized controlled trials was performed. The duration of the studies ranged from 8 weeks to 6 months.

The interventions varied widely, including both single-strain probiotics like L. plantarum and L. reuteri and multistrain mixtures, which included different strains of Bifidobacterium and Lactobacillus. Additionally, some interventions included formulated products that combined probiotics with nutritional supplements (e.g., the amino acid leucine). The control interventions were primarily placebos. Two studies also prescribed resistance training and physical activity to the intervention and control groups.

Probiotic supplementation had a large effect size on both muscle mass and strength in older adults compared to control groups. However, there was a high level of heterogeneity across the studies.

Overall, the results of this study should be considered exploratory. The high heterogeneity of the findings indicates that the studies differed widely in their study designs, interventions, and outcomes. For instance, 2 studies also prescribed resistance training or physical activity for the intervention and control groups in addition to the probiotics. Furthermore, the improvements in muscle mass were strongly influenced by 1 study with a very large effect size, whereas the other studies only showed small and not statistically effects. The probiotic interventions also varied widely between the studies, making it difficult to recommend specific probiotics.

Although the precise mechanisms underlying the potential benefits of probiotics on muscle mass and strength remain unclear, several hypotheses have been proposed. Probiotics may reduce inflammation in the gut,^[1] leading to systemic anti-inflammatory effects that could enhance muscle function. Additionally, probiotics might improve the absorption of essential nutrients such as vitamins^[2] and amino acids^[3], which are crucial for muscle growth and repair. Certain probiotics can also cause fermentation of dietary fibers to produce short-chain fatty acids,^[4] potentially influencing muscle metabolism.^[5] Further research is needed to fully understand the mechanisms behind the observed associations between probiotics and muscle health.