No guts, no glory! - Gut Health

The importance of gut health to the athlete and fitness enthusiast:


The gut microbiome is the term used for the beneficial gut bacteria that reside within the body, you've probably heard about them, they determine our overall health & wellbeing whilst playing a pivotal role in inflammation. Inflammation which can greatly interfere with an athlete’s performance & recovery. They either exacerbate it or help reduce it depending on the balance of bacteria within the gut. A small amount of inflammation is natural as it assists with adaptation to exercise and muscle repair.

Prolonged inflammation, often goes unrecognised but is seen and felt systemically is problematic, not just in the short term but in the long term.

Prolonged inflammation can arise from factors such as: psychological & physiological stress that an athlete experiences almost daily from their diet and lifestyle (intense prolonged levels of training, poor sleep, travel, medications, alcohol, emotional stress, poor nutrition) and I would strongly emphasise poor gut health here. When it comes to athletes, their gut bacteria play a significant role in how well they perform and recover.

Intense exercise not only alters the composition of an athlete’s gut bacteria, it increases their gut permeability, most athletes have what we functional practitioners’ term as 'leaky gut'. It does what it states on the tin. Allowing contents of the intestines to translocate into the blood stream stimulating an inflammatory immune response which is no longer localised (contained within the gut walls, which in itself is problematic) but now becomes systemic (generalised) wreaking havoc on the body.

Leaky gut fans the flames of inflammation and can lead to other issues such as food intolerances/sensitives, allergies (prolonging inflammation), brain fog (leads to poor decision making), mood changes, headaches, joint/muscle pain (recovery is slow), increased upper respiratory tract infections, immune suppression (missed training days), GI disturbances (bloating, cramping, diarrhoea, constipation), fatigue and all of this is just the tip of the iceberg. Athletes need to place greater care to personalised nutritional strategies to help attenuate inflammation.

Energised or Exhausted?

Good gut bacteria keeps energy levels sustained thus leading to better performance, increased energy, delayed fatigue and decreased lactic acid build-up. Researchers have recently demonstrated in ultramarathoners andOlympic trial rowers who participated in high intensity exercise, they produced high levels of a bacterium called Veillonella. They also demonstrated that following intense physical activity, the stool samples from these athletes had higher levels of bacterial genes involved in breaking down lactate to propionate. This is beneficial as propionate can be used to produce glucose when energy demands are high. The study was small, but has led to further studies of the Veillonella bacterium to see what benefits, if any, it can elicit in endurance athletes. Gut bacteria promotes digestion and absorption of nutrients for energy production, but in the colon, complex carbohydrates are fermented to produce short-chain fatty acids used for energy production, namely, butyrate, acetate and propinoate.

Research papers suggest there’s a large diversity of bacterial species that may be beneficial to exercise showing that adaptations to exercise may be greatly influenced by gut bacteria. Healthy bacteria create B-Vitamins that are heavily involved in energy production. They also communicate with other cells in the body to regulate blood sugar helping us to avoid fluctuating energy levels. What’s more, a healthy gut creates, and regulates neurotransmitters (like serotonin and tryptophan), the chemicals in the brain & the body responsible for happiness, motivation and sleep - all of which is linked to how we feel - ENERGISED OR EXHAUSTED.

Mental Wellbeing

As unusual as this may sound, gut microbes (bacteria) talk to our brain through their communication highway known as the Vagus nerve. This means they play a pretty big role in the state of mental health. When gut microbes become imbalanced, they can directly contribute to poor mental health and associated mood disorders.

Nutritional interventions and supplementation with probiotics can help to alter the gut microbiome and in doing so may help to improve symptoms caused by both psychological and physical stress whilst positively supporting the function of the gastrointestinal tract, easing joint and muscle aches/pain, reducing insomnia, addressing low energy, headaches and frequent colds and infections. Now it gets confusing, why? Because research shows that exercise promotes a diverse community of microbes both in a negative and positive light. BUT…if the body is pushed too hard with physical and psychological stress the impact on gut bacteria can be significant and detrimental to the health of the host.

In my opinion, it's a fine line when it comes to exercise intensity and gut health. Exercise-induced alterations of the gut microbiome may provide exercise-related benefits on GI function, mood and immunity but it can just as easily send it in the opposite direction, placing everything out of sync, causing an athlete to experience health issues. Take home message - the gut-brain axis is an invisible hand that shapes mental stamina, which is essential for professional athletes who can’t afford to collapse under pressure. To keep mental health strong, seeking support and having a nutritional program specifically tailored to their individuality as well as for their sport is the best way to stay fighting fit both mentally and physically.

Nutrient Absorption

A healthy, well-balanced microbiome within the gut have the responsibility of breaking down and absorbing nutrients from food so that those nutrients can be converted into energy. Athletes give some thought to what is going into their body, although from my own personal point of view, without the knowledge of the impact that food and its quality will have on their gut, overall performance, recovery and wellbeing. Consideration needs to be given to how well their digestive tract is truly absorbing those nutrients. Given an athlete's body is under constant stress from prolonged intense exercise, psychological stressors (making a team, compeitions), lifestyle and diet stressors - their gut is likely to be inflamed which contributes to leaky gut. A condition were the gut’s mucosal barrier – which absorbs nutrients while preventing large molecules like bacteria, toxins, and germs in the gut from entering the bloodstream becomes compromised. Increased Intestinal Permeability can negatively affect health and greatly compromise an athlete's performance. It may also lead to more acute health issues such as systemic inflammation, joint pain, impaired thyroid function, malabsorption of nutrients (leading to reduced energy, increased fatigue, poor recovery) as well as digestive issues (bloating, cramping, constipation or diarrhoea).


Eating the right food to help maintain a good functioning gut should be of priority to all athletes. Just as much as it is important to eat the right foods to help beneficial microbes thrive and survive, it is just as important to focus on what foods should not be in the diet, which unfortunately, when you look at the traditional sports nutrition approach may be included.

These are things such as the overconsumption of meat, processed foods, white refined foods, sugar, artificial sweeteners, caffeine, alcohol and the use of medications such as NSAIDS, these can all greatly disrupt gut health. Slowing down the digestive process, interfering with absorption and contributing to inflammation both in the gut and systematically throughout the body.

An unhealthy gut is significantly associated with poor sleep. Gut bacteria have the ability to control levels of various hormones such as the stress hormone, cortisol, the feel good hormone, serotonin and GABA, helps to decrease brain activity, all of these can affect the quality of sleep. Sleep that is vitally important to not only athletic performance but for recovery & mental health. Bacteria can also affect the production of melatonin, required in the body's sleep/wake cycle. Good sleep, gut health, energy levels, performance and recovery all exist to provide athletic support but if not looked after properly and one goes astray, this has a knock-on effect which can greatly negatively impact an athlete.

Athletes know they need sleep to perform well.

Are they getting enough sleep? Maybe not.

Do they know that sleep-inducing neurotransmitters are generated within their own gut and that the gut relies on the colonisation of healthy bacteria, along with the right foods to sustain their growth as well as to prevent localised & systemic inflammation that is detrimental to performance, recovery & overall health.....I think I can say for certain that they answer would be no. But I am sincerely, hoping that my blog posts will help them as well as others to rethink their health and their approach to food and lifestyle choices.


The body has an antioxidant defence system that uses antioxidant enzymes to keep the body healthy.

Athletes need this system in order to perform well and recover quickly.

A healthy antioxidant status is associated with balanced gut bacteria. Their involvement in the antioxidant system helps: Prevent tissue damage from exercise Protects against intense exercise-induced oxidative damage Is associated with physical status Reduces physical fatigue Improves exercise performance Intense sustained exercise and high-level competitions generate large amounts of free radicals that may exceed the buffering capacity of the body. This makes athletes susceptible to increased oxidative stress and more likely to increased systemic inflammation.

Gut bacteria have a significant role in inflammation either increasing or decreasing levels.

Inflammation interferes with athletic performance, slows recovery and is the root cause of many chronic diseases. Gut microbiome imbalance or dysbiosis as it is technically referred to is associated with inflammatory conditions – so it’s important we maintain a healthy microbiome to help reduce systemic inflammation. Research shows that improving gut health reduces systemic inflammation, which provides both short term relief and an improvement in long-term health. Improving bacteria balance and a diverse composition of same provides an environment which helps to decrease the impact of stress athletes place on their bodies.


Clark, A & Mach, N (2016) Exercise-induced stress behaviour, gut-microbiota brain axis & diet: systematic review for athletes; Journal of International Society of Sports Nutrition; 13-43

Galland,L (2014) The Gut Microbiome and the Brain; The Journal of Medicinal Food 17(12), 1261-1272

Lee, Elaine et al. (2017) Biomarkers in Sports & Exercise, Tracking Health, Performance & Recovery in Athletes; Journal of Strength & Conditioning Research, 31(10) 2920-2937

Mach, N., Fuster-Botella. D (2017) Endurance exercise and gut microbiota: a review; Journal of Sport & Health Science, Vol. 6 (2) 179-197

Neish, A. (2013) Redox Signaling Mediated by the Gut Microbiota; Free Radical Research

Scheiman et al (2019) Meta-omics analysis of elite athletes identifies a performance enhancing microbe that functions via lactate metabolism; Nature Medicine, (25) 1104-1109

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