Sports Nutrition & Gut Health

sports nutrition & gut health

Welcome back to our series on Sports Nutrition. In this week’s article on Sports Nutrition & Gut Health we will look at the role of the gut (our favorite topic!) in Sports Nutrition. For a review of last week’s discussion of how much to eat and which macronutrients to eat for sports performance, see here.

We have written extensively about gut health, starting with our series of articles on the Gut-Brain Axis. We also mention the gut in most of our articles. It is so critical to overall health that it cannot be avoided. This week we are going to look at gut health and how it specifically relates to athletic performance. There is some exciting new research being done on this topic and we will present it to you here.

** Please note: If you want the short summary version of this article with a video, then please click here **

Athletic performance depends on age, gender, genetics, training history, fitness level of the athlete and the type, duration, intensity and frequency of training (Hughes, 2020). The state of the gut microbiome may also influence sports performance in response to training and nutrition.

Very few studies have looked at differences in performance and the role of the gut. This is an area that may be able to provide an edge for athletes, who will usually look for any possible advantage to enhance performance (Hughes, 2020).

A good example of a well-known athlete improving gut health and experiencing a tremendous uptick in performance is the top ranked, elite tennis player Novak Djokovic. Djovokic was a strong tennis player but suffered from symptoms, such as difficulty breathing and fatigue, during championship matches for years. It was thought that the issue was due to his level of fitness but it turned out that he had digestive issues. In 2010, Djokovic went gluten- and dairy-free and dramatically improved his performance (Campbell, 2019). He worked with a Nutritionist and identified that he was sensitive to both gluten and dairy (Campbell, 2019). He eliminated both from his diet and within 12 months, became healthier, more energetic and mentally sharper (Campbell, 2019). Since then, he began winning more Grand Slam tournaments and has dominated men’s tennis ever since.

See our article here, to understand why going gluten free can improve digestive health and specifically, leaky gut.

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Our gut microbiome is not a fixed entity. It adapts and responds to environmental factors (diet, exercise, toxin exposure, stress, antibiotics use and many other factors) (Hughes, 2020).

Athletes have a different gut microbiome composition from those of sedentary people (Jäger R, 2019). Differences are due to the amount of exercise they do, the effect of exercise on the gut microbiome, the amount of protein they consume, the effect of diet & nutrition on the gut microbiome and the effect of the gut microbiome on performance (Hughes, 2020) and (Jäger R, 2019).


It is not easy to isolate the effects on the gut of exercise alone, as athletes tend to eat differently from the general population (Jäger R, 2019). For example, increased protein intake by elite rugby players could account for many of the observed differences in the gut microbiota (Mailing LJ, 2019). More research needs to be done on whether exercise independently changes the gut microbiota, as it is somewhat of a ‘chicken and egg scenario’ as to whether an athlete’s gut is different because he/she eats differently or exercises consistently (Mailing LJ, 2019).

The key differences of the gut microbiome of athletes compared to non-athletes are linked to enhanced fitness (Jäger R, 2019).

Athletes have higher microbiome diversity, meaning they have a greater variety of different types of gut bacteria. More diversity is associated with better health.

  • Athletes have a more diverse, metabolically favorable gut microbiome due to consistent good nutrition and physical activity over years, which is necessary for professional sports participation (Jäger R, 2019).
  • The gut microbiota of professional rugby players has been found to have greater diversity (Mailing LJ, 2019).
  • Studies find increased microbial diversity in athletes compared with non-athletes (Barton W, 2018).

Athletes have a higher number of health-promoting bacteria in the gut.

  • Women who performed at least 3 hours of exercise per week had increased levels of Faecalibacterium prausnitzii, Roseburia hominis, and Akkermansia muciniphila (Mailing LJ, 2019). F. prausnitzii and R. hominis produce the SCFA butyrate (more on SCFAs later) (Mailing LJ, 2019), and Akkermansia muciniphila is associated with a lean body mass index and improved metabolic health (Mach N, 2017).
  • Certain gut bacteria consistently react to exercise (Hughes, 2020). For example, Lactobacillus, Bifidobacterium and Akkermansia increase and Proteobacteria, Turicibacter and Rikenellaceae decrease with exercise (Hughes, 2020).
  • Exercise increases bacteria which can modulate immunity, improve barrier functions and stimulate bacteria capable of producing substances that protect against GI disorders (Jäger R, 2019). For example, elite runners have more Veillonella, a strain of bacteria that provides a metabolic advantage for endurance exercise (Jäger R, 2019). Studies with Veillonella show a 13% increase in endurance performance (Scheiman J, 2019).
  • The athlete gut microbiome is better able repair tissue and absorb energy from the diet, reflecting the tissue adaptation that occurs during intense exercise and elite sport (Barton W, 2018).

Athletes have more short chain fatty acid (SCFAs), which are produced by microbes in the gut (Jäger R, 2019). 

  • SCFAs are very important for gut health. They are products of gut bacteria which ferment fiber from carbohydrates from the diet. They are key energy sources for certain cells. Examples of SCFAs are acetate, propionate and butyrate. Endurance exercise produces SCFAs to be used as energy (Okamoto T, 2019).
  • Butyrate-producing bacteria strains increase with exercise, which can change lean muscle mass (Hughes, 2020). Butyrate-producing bacteria correlate positively with athletic performance (Hughes, 2020). Butyrate is the key fuel source for colonic cells and has anti-inflammatory properties. It also inhibits pro-inflammatory molecules of the immune system.

SCFA concentration can influence exercise capacity (Hughes, 2020). One study on mice looked at a low carbohydrate diet vs. a high carbohydrate diet to test how the gut microbiome affected exercise capacity (Hughes, 2020). Treadmill running time, muscle mass and SCFA production was decreased in the low carb mice (Hughes, 2020). When mice on the low carb diet (with lower SCFAs) were given a fecal microbiota transplant (FMT) from the high carb mice and a prebiotic, the reduced exercise capacity was reversed (Hughes, 2020). In addition to increased exercise capacity, the low carb + FMT + prebiotic mice had an increase in SCFAs, which suggests that SCFAs influence capacity for exercise (Hughes, 2020).

Exercise increases the Bacteroidetes-Firmicutes ratio.

  • This ratio is associated with obesity. In one study, data showed that obese adults have a significantly higher level of Firmicutes and lower level of Bacteroidetes compared to normal-weight and lean adults (Koliada A, 2017).
  • The ratio of Firmicutes to Bacteroidetes (F/B ratio) is significantly higher in obese individuals than in lean individuals and a decrease in the ratio in obese individuals correlates with weight loss (Armougom F, 2008).
  • It makes sense that athletes would have a higher Bacteroidetes to Firmicutes ratio as they tend to be leaner than the general population.

Exercise can reduce inflammation, by downregulating pro-inflammatory cytokines and upregulating anti-inflammatory cytokines, which are cells of the immune system (Mailing LJ, 2019)

Exercise increases gut motility and bile acid secretion, which contribute to a balanced gut and enhance overall gut function (Mailing LJ, 2019). Low motility and/ or low bile acid secretion contribute to gut dysbiosis.

Overall, exercise represents a hormetic stressor to the gut that stimulates beneficial changes and improves the long-term resilience of the gut barrier (Mailing LJ, 2019).

  • A hormetic stressor creates a favorable biological response to low exposures to stressors.
  • In the short term, acute exercise impairs the gut barrier function. But over time, athletes have lower levels of LPS (these are endotoxins that damage the gut) and increased heat shock proteins (these inhibit the breakdown of tight junctions) vs. sedentary people (Mailing LJ, 2019). Both low LPS and high heat shock proteins are positive for gut health.

Interestingly, most gut bacterial strains and SCFAs that increased with exercise decreased once exercise was stopped (Mailing LJ, 2019). One study had a 6-week sedentary ‘washout’ period where participants did not exercise for 6 weeks (Mailing LJ, 2019). During this time, both diversity and SCFAs decreased (Mailing LJ, 2019). This shows that the effects of exercise on the microbiota appear to be transient and reversible (Mailing LJ, 2019).


As of 2017, there is no evidence that the absence or presence of one single species (bacterial, fungal, viral or other) is associated with better performance or health in athletes (Mailing LJ, 2019).

  • The gut microbiome is vital for the proper function and development of the body (for energy metabolism, the inflammatory response, stress resistance, oxidative stress), but it is not clear which are the key species and whether the microbiome’s overall function is more important than any individual member of the microbiome in terms of impact on the exercise response (Mach N, 2017).
  • Endurance swimming time was longer for mice with a gut microbiome vs. that of germ-free mice (i.e. with no gut bacteria), suggesting that gut bacteria composition is crucial for exercise performance (Mach N, 2017).
  • In young adults, overall microbial diversity and abundance of butyrate-producing bacteria were positively correlated with cardio fitness levels (Mailing LJ, 2019).


Probiotic supplements are live bacteria that increase the number of beneficial bacteria in the gut (Jäger R, 2019). They benefit gut and immune health by modulating the immune response, maintaining gut lining, keeping pathogens out of gut tissue and producing vitamins, SCFAs and other molecules involved in gut–brain axis communication (see our article here on gut-brain axis communication) (Jäger R, 2019). Probiotics are available either in supplement form or in fermented foods (yogurt, sauerkraut, kimchi, kombucha and other fermented foods).

Probiotics can improve performance in athletes and physically active individuals, although the results are mixed (Jäger R, 2019). Some studies showed improvement in aerobic performance while others showed no improvements (Jäger R, 2019). In resistance exercise, i.e. weight lifting, probiotics increased recovery and reduced muscle soreness (Jäger R, 2019).

The most obvious benefit of probiotics on athletic performance is the impact on the immune system. Intense exercise can reduce the amount and function of immune system cells (natural killer cells and T cells) and increase inflammation in the short term (Jäger R, 2019). This can suppress immune function in athletes. As a result, athletes may frequently get sick, especially with respiratory tract infections including the common cold, or GI issues, from heavy training loads. This can interrupt training and impair their ability to compete. Probiotics can support the immune system in many ways, resulting in an overall decrease in respiratory infections in athletes (Jäger R, 2019). Probiotics lead to some changes in immune markers that are protective for the immune system (Jäger R, 2019).

Strenuous and prolonged exercise can also be stressful for the gut. Possible gut symptoms of athletes include abdominal cramping, acid reflux (heartburn), nausea, vomiting, diarrhea, leaky gut, reduced nutrient absorption and lower performance. Taking probiotics can help, but study results are mixed (Jäger R, 2019). The most clear benefits of probiotics is the decrease in zonulin (which causes leaky gut, see our article on this here), a decrease in pathogens, a decrease in leaky gut and shorter duration of GI symptoms (Jäger R, 2019).

In athletes, one study found the administration of Lactobacillus and Bifidobacterium strains help to maintain general health, improve immune function, help gut permeability, reduce oxidative stress and better obtain and absorb energy from plant-carbohydrate sources. (Mach N, 2017).

Whilst research on gut health and athletic performance is still in the early phases, it is clear that exercise changes gut health for the better. It is also clear that optimizing gut health will improve performance, as well as general health. In order to be in the best health possible, improving gut function is an essential area to target with an experienced FM practitioner.

What you can do to help improve gut health for athletic performance?:

Add a probiotic blend with Lactobacillus and Bifidobacterium strains, like our Good Gut Bugs + SB product (available through our clinic if you text 720-722-1143 for more info)

Do an elimination diet for 30-90 days and then re-introduce foods one at a time to check for negative reactions (1 food every 3 days)

Gluten, dairy, corn, soy and eggs are all common allergens so start by eliminating these first

To take it a step further, also eliminate nuts, fish and shellfish

Eliminating nightshade vegetables, seeds, all grains and legumes / beans can be highly effective for identifying food sensitivities (but of course is fairly restrictive while doing it)

When re-introducing, it is important to add back just 1 food every 3 days and if there is a negative reaction, remove that food for at least another few months and test it again in the same way. If there is still a negative reaction it can be removed long-term.

** Please stay tuned for next week’s article on Sports Nutrition **

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