Gastrointestinal discomfort is one of the most common issues an ultra-endurance athlete will face during competition, with an incidence rate of 60-96% . When you undergo intense exercise, the rate of blood flow increases around the body to demanding organs such as the skeletal muscles. As a result, the digestive system may experience inadequate blood flow, as other organs are prioritised. This can lead to inflammation and irritation of the gastrointestinal tract . The most commonly reported symptoms include dizziness, nausea, stomach or intestinal cramps, vomiting, and diarrhoea .
If the gut microbiome is healthy, it will optimise systems that prevent this inflammation, reducing discomfort and allowing you to perform without interruption. This can be achieved by including an appropriate array of prebiotics in your diet, a type of fibre that acts as food for the microbiome. Prebiotic substances can help to increase the abundance of healthy bacteria in the gut and reduce gastrointestinal issues during endurance exercise . The potential of prebiotics to exert an anti-inflammatory effect has been identified as particularly relevant to ultra-endurance athletes due to the prevalence of increased gut permeability and inflammation .
Having a diet high in prebiotic fibres will also provide the nutrients that gut bacteria need to produce beneficial metabolic by-products, called postbiotics. These postbiotic substances help to modulate many aspects of the host metabolism and immune system . Optimising metabolic function will result in greater energy production for endurance capacity, whilst a more robust immune system helps to prevent illness. Therefore, the effects of a healthy gut microbiome on endurance performance can also be attributed to the indirect maintenance of good health and, subsequently, the ability to optimally train and compete .