The Marathon Endurance Study

Four weeks of probiotic supplementation reduces GI symptoms during a marathon race 


This study was designed to evaluate the effects of probiotic supplementation on gastrointestinal (GI) symptoms, circulatory markers of GI permeability, damage, and markers of immune response during a marathon race.
The marathon runners taking Lab4 probiotics experienced fewer and less severe gut symptoms during their training period and marathon race.
The reduction in gut symptoms was associated with maintaining running speed during the latter stages of the race.


This randomised, double-blind, placebo-controlled study aimed to assess the effect of Lab4 probiotic supplementation on gut symptoms, race time, intestinal permeability and immunological markers during marathon training and racing.



Gut symptoms during 28-day supplementation period

  • The number of moderate gut symptoms and number of days with these symptoms were significantly reduced in the last 14 days of Lab4 probiotic supplementation compared to the first two weeks (*P<0.05).
  • Gut symptoms during the marathon race

  • A significant reduction in the severity of gut symptoms was seen in Group 2 compared to Group 1 (*P=0.01) during the final third of the race.
  • A signification association between gut symptoms during the race and reductions in running speed was observed, especially towards the later stage of the race.
  • Race speed

  • Reduction in the average speed from the first to the last third of the race was significantly greater in Group 1 (14.2% reduction) compared to Group 2 (8% reduction, *P=0.03).
  • Conclusion

    Lab4 probiotics supplementation protects endurance runners from gut disturbances during a marathon race and may help to maintain running pace during the latter stages of racing.


    Pugh JN et al 2019. Four weeks of probiotic supplementation reduces GI symptoms during a marathon race.
    European Journal of Applied Physiology 119: 1491-1501

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