How do Probiotics affect Sports Performance?

Probiotics, not to be confused with prebiotics, are live bio cultures that we can consume through a variety of different forms. Sometimes through food, like with kraut or kimchi, sometimes through drink, like with kefir, and sometimes through supplementation, normally taken in the form of capsules.

We’re focussing on the use of probiotics in sports performance, so make sure you understand a little bit about probiotics first. For an introduction to probiotics, check out our previous blog post here on the importance of gut health.

The field of probiotics and gut health is rapidly becoming more and more prevalent in research, and in the last few years, the use of probiotics in sports performance has been an area of interest for sports scientists.

So what does the research to date show, and how can probiotics aid your performance?

So far, research has shown that probiotics can:

  1. Increase immune health.
  2. Improve gut function.
  3. Stimulate helpful metabolites (a by or end-product of metabolism) that help protect against other gut disorders.

For the latter, it has been found in some elite runners that there is a greater abundance of the species of bacteria reported in their gut. This has been found to benefit the individual by converting lactate (also known as lactic acid), reducing the overall build-up in muscles and aiding runners with their endurance as a build-up of lactic acid is what causes cramp.

Ultimately, diversity in the gut microbiota is very beneficial.

How does diversity help?

As mentioned, a diverse gut microbiome is very important and can contribute to enhanced sports performance, as well as optimising general health, too. 

More diversity means better overall health, as different bacteria are responsible for breaking down and digesting different things. They will outcompete each other, and so having a diet that lacks variety can result in non-diverse gut microbiota.

For example, if you regularly consume a diet high in fat, the bacteria that break down fat will outcompete the bacteria that do not tend to be fed as regularly for space and become more prevalent, meaning your body becomes more adapted to digesting fat.

As can be assumed, a decrease in diversity in the gut can be a sign of unhealthy gut microbiota and has been associated with the development of chronic conditions, such as diabetes and obesity.

Having a skewed or non-diverse microbiota can be reversed, but it can take time and energy to do so.

What are the clinical benefits of probiotics?

70% of the immune system is based in our digestive tracts, therefore not only can probiotics help with stomach-related problems or pain, but they can also improve immune health and, of course, sports performance.

Increasing sports performance is not limited to elite athletes either (although the results they see will likely be more significant than an everyday athlete). In fact, amateur athletes can still see benefits in strength and endurance and even flexibility.

A study in 2019 (2) assessed the impact of probiotics versus a placebo tablet on a group of athletes competing in a marathon that was arranged for the study. Typically, runners will experience significant nausea and the urge to use the toilet during a race and while training, with around 30% of runners having moderate to worse symptoms during a race than on an average day. Although interestingly, this amount was higher during training, with around 40% of participants experiencing the same.

The study aimed to see if taking a course of probiotics leading up to the race would impact their symptoms at all. 

This was assessed through a double-blind approach, meaning the participants and the researchers themselves were not aware of who had been prescribed the probiotic and who had been prescribed the placebo. All participants had their bloods taken, were given the same pre-race food, and had another blood test taken, along with a muscle biopsy, before the race.

During training, after two weeks, the probiotic group collectively reported a reduction in gut symptoms – this was not the case for the placebo group.

On the race day, those in the probiotic group were found to have significantly less severe symptoms in the final third of the race and additionally found that their pace did not slow as much towards the end of the race when compared with the placebo group.

The average finish time bore no significant difference across the groups.

It is important to note that all participants of the study were recreational runners (i.e not elite athletes), meaning that probiotics can certainly be effective in improving performance for all athletes – elite or otherwise. However, the mechanisms that are involved in this process are yet to be elicited.

How to keep a healthy gut microbiome

If you’re concerned about the health of your gut microbiome, you can help improve it. This can be through ensuring your diet is full of variety and three very important factors;

1. Tryptophan

Tryptophan is an essential amino acid found in foods like turkey, eggs and chia, and is a precursor for serotonin, one of our ‘happy’ hormones, and melatonin (synthesised from serotonin), which helps regulate our circadian rhythm.

2. Tyrosine. 

Tyrosine is another essential amino acid found in foods such as almonds, lentils, seeds and edamame. Both dopamine and adrenaline are synthesised from tyrosine – both important hormones for our day-to-day functioning. Dopamine is another ‘happy’ hormone, and adrenaline is what is responsible for our ‘fight or flight’ mode. 

3. ILA

Finally, there is indole-3-linoleic acid (also known as ILA). This can be found in your more traditional ‘gut health’-type foods, like kraut, kimchi, and kefir. The bacteria in our gut convert ILA to IPA (indolepropionic acid), which is one of the strongest antioxidants in the body and breaks down free radicals (unstable atoms formed during metabolism, which can be carcinogenic).

Having a diet that is rich in these three components can greatly improve your gut health.

What causes damage to the gut microbiome?

As with everything health-related, certain factors can cause harm to your microbiota;

  1. Consuming very little tryptophan, tyrosine or indole-3-linoleic acid will mean the bacteria do not thrive.
  2. Antibiotics and medicine can also impact the gut microbiota. While often imperative, antibiotics kill all bacteria in your gut – the good will nearly always outweigh the bad with antibiotics, but try to take preventative measures to not need them if possible (for example, having a balanced, healthy diet, exercising, and reducing stress where possible). 
  3. Lastly, stress. Because of the gut-brain axis (which you can read more about here), what is going on in your head will be felt in your gut as well, and minimising stress can be significant in improving your gut microbiota.

If you’re looking to improve your performance, regardless of whether you are an elite or amateur athlete, probiotic supplementation may be a helpful aid. Just ensure that you research the probiotics you use beforehand, as some strains included have little research on them.

Alternatively, add our Bio Cultures supplement to your plan instead, and see if there are any performance improvements yourself! 


  1. Durkee, S., Toth, L.,. (Year site published/updated) What role can probiotics play in sport performance?. [Inside Food Science, Food Matters Live]. 1st March 2022.
  2. Pugh JN, Sparks AS, Doran DA, Fleming SC, Langan-Evans C, Kirk B, Fearn R, Morton JP, Close GL. Four weeks of probiotic supplementation reduces GI symptoms during a marathon race. Eur J Appl Physiol. 2019 Jul;119(7):1491-1501. doi: 10.1007/s00421-019-04136-3. Epub 2019 Apr 13. PMID: 30982100; PMCID: PMC6570661.

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Meghan Foulsham

Published by Meghan Foulsham

Meghan's fascination with metabolism and the effect of diet on the body covered in her BSc Biochemistry, paired with being a passionate mental health advocate, led her to a Master's degree in Eating Disorders and Clinical Nutrition. Using this, Meghan works with clients to help them reach their goals in the most sustainable way, without sacrificing or risking their mental health.

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