The effects of supplementation with probiotics in runners Original paper

In this randomized controlled trial in recreational marathon runners, taking a probiotic supplement improved gastrointestinal symptoms but did not affect running performance, compared with a placebo.

The effects of supplementation with probiotics in marathon runners.

The outcomes assessed were performance on a 12-minute running test, gastrointestinal symptoms, gut microbiota composition, BMI, bone mineral density of the femur, emotional stability, and thigh muscle mass and fat.

19 recreational marathon runners (average age of 29; 15 men, 4 women) with no known health conditions.

The runners were recruited from the “Hangzhou Sunshine Running Team” in China.

In this 5-week randomized controlled trial, the participants took probiotics or a placebo daily. The probiotic supplement contained Lactobacillus acidophilus and Bifidobacterium longum (a total of 1.5×10⁹ CFU per day).

The participants were instructed to refrain from products that contain probiotics (e.g., yogurt) during the study and to maintain their usual training routine. The participants were also required to fill out a training diary during the study.

All of the outcomes were assessed before and after the intervention. Gastrointestinal symptoms and emotional stability were assessed using questionnaires, gut microbiota composition was determined from fecal samples, and bone mineral density and thigh muscle composition were measured with a DXA scan.

Gastrointestinal symptoms improved in the probiotics group, compared with the placebo group. There were also differences in gut microbiota composition between the groups at the end of the intervention, including higher amounts of Bacteroidetes, Firmicutes (including Lacticaseibacillus at the genus level), Proteobacteria, and Actinobacteria in the probiotics group.

The changes in the other outcomes did not differ between the groups, although there was an improvement in running performance in the probiotics group, compared with baseline.