The gut microbiome (a word used to describe all of the genetic material within a collection of microorganisms in a specific niche, such as the human gut) is a hot topic of research at the moment and its effect on our own health has been the subject of much discussion.
The gut microbiome has been linked with a number of conditions, including anxiety, gastrointestinal issues and irritable bowel syndrome.
So, what does this mean for the way we exercise? Spokes Performance Coaching's Will Newman considers the importance of 'mastering' your gut microbiome...
What is gut microbiome?
The microbiome is involved in many useful processes, such as the production of vitamins and fat storing hormones, as well as allowing the fermentation of certain food groups and preventing the overgrowth of harmful strains.
It's prudent to view the microbiome as a form of organ in itself, due to its massive role in the responses of the nervous, endocrine and immune systems.
It's thought that the microbiome develops as early as when you're in the uterus, with the passage through the birth canal leading to intake of bacteria and yeasts through your skin.
It's a subject of some controversy as to whether bacteria are present in the foetus, or whether they are sterile and, due to ethical reasons, this has only ever been studied in rodents.
Once in the world, human touch, breast milk and food allow the intake of more species which eventually inhabit the gut of the infant.
Breast-fed infants have more Bifidobacterium, which are more beneficial than the enterobacterium found in milk formula. It appears the pre-biotic nature of natural breast milk nourishes growth of already present bacteria.
By the age of five years old, children may have had many cases of gastroenteritis due to a reduced capacity for immunity, meaning a large variation occurs in the make-up of the microbiome over the years.
In adults, our diet, stress, sleep schedule, weather, environment, genetics, mood, sex life and even preference for certain foods influence our microbiome, which can be receptive to change in a matter of days or weeks.
Gut microbiome and general health
The overuse of antibiotics in the past has more recently been reconsidered due to the damage it does to your gut flora, killing all bacteria indiscriminately and ensuring even beneficial species are eradicated.
This can lead to negative strains 'possessing' the environment and can cause undesirable health outcomes. Even a simple caesarean section can reduce the transmission of bacteria from mother to baby and this can increase the risk of Type 1 diabetes, metabolic diseases and even depression. Vaginal birth may in fact play a role in helping healthy bacteria to thrive.
Overgrowth of the small intestinal bacteria due to changes in stomach acidity can also promote gastrointestinal conditions, bloating, diarrhoea and fatigue, but these are just the tip of the iceberg for microbiome disruption.
Cancer, diabetes, depression and other major health disorders are thought to stem partly from reductions in microbial diversity in the gut flora, as well as the propensity for individuals to respond to treatment.
Even a lack of exposure to certain bacterial strains can influence the digestion of and production of short chain fatty acids, which can cause immune changes and influence the development of breathing conditions like asthma.
So, we should not just view our stomach and intestines as distant and only for food – in the next 50 years I think this will be a fundamental area for scientific advancements.
How to personalise your approach to gut health
Our Nutritionally Fit page has a range of opinions and diets that people follow and we often see animosity aimed at those who take a different approach.
But, like with the sweat sodium losses that Precision Fuel & Hydration measure, there are huge individual differences in the composition of our microbiota. (Unfortunately, you can only sequence this through a stool sample, which is a bit more invasive than taking a Sweat Test!).
This may explain why some people can get great results on a high carbohydrate diet, whereas others thrive on ketogenic style diets. The microbiome plays a huge role in the digestion of material and even the storage of fat, and so we must be careful in buying into blanket "one-size-fits-all" recommendations.
Other ways your gut can affect your health and happiness
This area is still very much unravelling, but it has been known for years that the GI tract is its own entity. This two-way interaction allows the brain to relay signals to the gut, but also provides feedback in the opposite direction, meaning the gut can very much affect the brain. Although anecdotal, the sense of ‘gut feelings' - where you can somatically judge whether a decision is good or bad - actually rings true!
What’s more, the enteric nervous system that's part of your GI system is lined with serotonin receptors that are responsible for happiness, feelings of pleasure, satiety and motivation.
In individuals with conditions like IBS, sometimes a reduced regulation of serotonin affects the movement of the gut and causes dysfunction, which is relayed to the brain and may cause feelings of anxiety.
Even if you don’t have this condition, you may relate to feelings before races or big events where your bathroom habits change – this is your anxiety and nerves directly affecting your gut.
It's also thought that the gut flora affects mood and behaviour significantly, but as yet the research is still being conducted to understand how and why. Promisingly, rodent studies have found differences in mood behaviour between microbially sterile and bacterial-supplemented models.
How your gut microbiome can impact your athletic performance (and vice versa)
It appears that significant exercise following rest may promote low level inflammation in the hours following exercise but exercising on a regular basis can also influence the composition of the gut microbiome through the production of mediating compounds which reduce that inflammation.
One study with elite rugby players a higher muscle turnover and cardiorespiratory fitness was indicated through the strains found in their faeces. The conclusion was that there is a link between aerobic fitness and the composition of your microbiome.
The extent to which your diet affects the microbiome constitution of athletes is unknown. Is it the exercise which changes the microbiome, or is their microbiome healthier because of their typical athlete diet?
It would be interesting to look at different diets in the athletes (e.g. fat adapted, high carb) and look at variations. Your body generally selects the most beneficial strains of bacteria to support its homeostasis, except in periods and states of disrepair.
Strenuous prolonged exercise, like IRONMAN triathlons and ultra runs, increases intestinal permeability (the amount of water which can travel into large intestine).
Likewise, blood is redistributed away from the gastrointestinal tract for respiration, and thus the gut is left in a relatively ischaemic ('low oxygen') state, hampering it's performance.
This often leads to diarrhoea, stomach pain and dehydration in individuals who do not recover properly, or who are not used to the level of exercise. However, this is less of a concern for those who have exercised for a long time (as adaptation has occurred and exercise will promote a decrease in inflammation).
In another study, differences in the composition of intestinal microbiome in athletes was found to be responsible for 20% of the variation of the subject's VO2 max. In other words, those who had the highest VO2 max had an increased diversity of certain species of bacteria.
This was after dietary differences and genetic components were excluded, suggesting that the action of exercise in promoting greater autonomic control at rest has positive effects on gut function.
Beneficial bacteria are associated with protein intake, which is often elevated in athletes who focus on recovery. But, was it exercise that caused a beneficial microbiome composition, or do athletes simply eat more antioxidant foods and probiotic supplements?
Even getting enough sleep, staying relaxed through meditation and/or exercising less can have a big impact on your microbiome constitution.
If you get stomach cramps and GI distress after hard races, it may be worth supplementing with probiotic supplements to see whether this reduces the symptoms.
What's next for research into the gut microbiome?
Going forward, using DNA testing initiatives like Fitness Genes, individuals will be able to understand more about their disease risk and athletic performance.
My gut feeling (pun intended) is that the future will involve more personalised healthcare and the supplementation of strains of microbiota in order to support health outcomes and physical performance.