The human body is a complex interaction of a number of different systems. When it comes to exercise, we tend to be interested in the physiological systems, such as the cardiovascular system (the heart, arteries and veins, which transport blood, and therefore nutrients, to our working muscles), the pulmonary system (the lungs, which allow us to absorb the oxygen that our cardiovascular system transports), and the musculoskeletal system, which allows us to move.
In recent times, sports scientists have become more interested in the endocrine system, which looks at how different hormones might impact exercise performance and adaptations, and also the immune system, in an attempt to stop athletes from getting ill when they exercise. Even more recently, the brain has become subject to an increasing amount of attention, and the results from these indicate that the brain is incredibly important in deciding when to stop exercising due to fatigue, and also how you respond to stress, which in turn can impact how well you adapt to exercise.
All of these systems have one thing in common, in that they are commonly thought of as parts of our body. These systems are made up of our cells, systems within these systems that contain our DNA, and govern all of life’s processes. There are varying estimates of how many cells make up the human body, but it is perhaps around 10 trillion. That’s a lot of cells, but you might be surprised to hear that the human body contains 100 trillion cells. This means that, for every one cell that makes up our body, there are ten cells that aren’t part of our body. So where might these cells be, and what are they? Well, they tend to be things like bacteria, viruses, and other micro-organisms, and they can be found all over. Our skin, for example, contains millions of different bacteria on its surface. If we’re unlucky, this might include parasites, or things like head-lice. However, the vast majority of these extra cells are found in one place; our stomachs. Here, these cells form the bacteria that we collectively call the microbiota. They have a number of different functions, including breaking down our food to provide energy, and improving our immune function.
The microbiota, and its genetic make-up (called the microbiome), are the latest system within our bodies to capture the interest of sports science. And with good reason; due to the variety of roles played by our microbiota, there are a number of ways they can impact our performance. It seems that, overall, the more diverse our microbiota, the healthier we are. Elite athletes are also more likely to have an increased diversity of the microbiota, as evidenced by a 2014 paper published in the journal Gut. The same is true when it comes to obesity; on average, obese people have less diversity compared to lean individuals, and, more remarkably, transplanting the bacteria from an obese mouse into a lean mouse causes it to become obese!
What is also becoming clearer is the impact that the microbiota can have on the brain. This was made clear in a recent review article, with the bacteria in our stomach controlling the release of hormones that can make us feel more relaxed, or more stressed. This can also be important during exercise, because our emotions can directly influence our exercise performance.
All of this points to the fact that we should make an effort to ensure that our microbiota are both healthy and diverse. Right now, the best advice is to eat a varied diet rich in whole foods; plenty of vegetables and fruits, healthy fats, and wholegrains. Fibre can be particularly useful, so all the more reason to eat your vegetables. Foods rich in bacteria, such as fermented foods and blue cheese, can also be really good for your stomach bacteria. On top of this, it’s probably a good idea to avoid refined carbohydrates and processed foods, as well as an unvaried diet, as this can reduce the diversity of these bacteria. Some evidence also suggests that the use of probiotic supplements also improves microbiota diversity, and also improves immune function, keeping those colds at bay.
Putting all this together, we can see that sensible exercise and a varied, healthy diet are what keeps our stomach bacteria both effective and diverse. The effects of this diversity mean that we can improve both our health and our exercise performance, so they shouldn’t be ignored. Finally, a probiotic supplement by useful, but only if your diet doesn’t have the variety required, or if you’re involved in heavy training.