Our gut is host to billions of bacteria which, when in balance, are known to confer a host of health benefits on the host. They are known to impact metabolic function, immune function, the production of certain B vitamins and short chain fatty acids, essential for the health of the gut lining. Whilst the research in this area is still in its infancy, it is known that the make-up of an endurance athlete’s gut microbiome differs in diversity to the average, more sedentary individual. Recent research has suggested that a particular specie known as Veillonella can break down lactic acid, which may play a role in causing ‘stitches’ during strenuous activity, via conversion into the fatty-acid propionate (see attached article). There are a growing number of studies investigating the impact of probiotic (and prebiotic) supplementation in athletes with some interesting results and an area to consider when looking at an athlete’s overall health from a functional perspective. However, personalising the bacteria to the individual is still an emerging area of knowledge.