Athletes who undergo very high training loads frequently complain of gastrointestinal distress.

It’s been reported that 46% and 54% of elite athletes experience upper and lower gastrointestinal discomfort. Of which these numbers increase to 53% and 60% during competition.

These gut issues are commonly associated with the reduced blood flow to the gut during exercise which consequently increases the integrity of the gut wall, and therefore it’s permeability (leakiness).

As a result, unwanted bacteria and toxins can enter the blood and cause an inflammatory response and interfere with athletic performance. In addition to this, intestinal wall ‘injury’ can impair the uptake of fluid, electrolytes and carbohydrates, which further compounds impacts performance.

Athletes are recommended to ‘train the gut’ and follow a low residue/fibre diet surrounding competitions to negate these issues. But what about probiotic supplementation?
Probiotics consist of bacteria and have been given a great deal of attention due its putative health benefits through their interaction with the gut microbiome.

Of interest, the composition of your gut microbiome can positively affect exercise performance (usually time to exhaustion) and reduce susceptibility to upper respiratory infections in fatigued athletes.

Knowing this, what is the potential impact of 90 day supplementation in elite cyclists (Schreiber et al, 2021)?

Over the 90 days, the cyclists consumed a multi-strain probiotic (15 billion CFU) and continued with their normal diet and training regime.

The keen eyed reader would notice that this in itself is a limitation…and ultimately, controlling an elite athlete’s diet and training surrounding competition is never really going to happen.

Since both diet and training can alter gut flora, it’s difficult to determine exactly how impactful probiotic supplementation was.

That being said, the elite athletes who supplemented with probiotcs did experience significantly fewer issues with nausea, heartburn, belching and vomiting. Interestingly, those who supplemented had lower ratings of perceived exertion during maximal testing – most likely, as a result of reduced gut issues.

Not surprisingly, they didn’t see performance improvements due to supplementation – again, this is highly likely because they were all on different training programmes.

The improvements in gut discomfort could be a direct result of improved gut integrity and under different testing conditions, could improve performance as seen in previous studies using probiotic supplementation.

Therefore, I would highly encourage athletes to incorporate probiotic rich foods (fermented products) into their diet year round.

However, I would only periodise supplementation around intensive competition periods only. i.e. in-season or during the weeks leading into target events.

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