The gut microbiome is one of the big research themes attracting public attention. The microbiome is made up of the resident bacteria, viruses and microbes that colonise our gastrointestinal tract. Immunity, mental health, diabetes and even body weight are among the fascinating areas covered in the ever-growing research field of gut microbiota.
One-third of our gut microbiota is common to most people, while two-thirds are specific to each one of us. This makes our gut microbiome reasonably unique
You are what you eat, and so are the bacteria that live in your gut. The different strains of bacteria change depending on the types of food eaten. Researchers have now moved out of the realm of diet and are looking at how exercise could also affect the gut microbiome.
In the first of two studies, US researchers transplanted faecal matter into germ-free mice from mice who were exercised and mice that had been kept sedentary. The germ-free mice were then inoculated with the microbiome fingerprint of mice exposed to different activity levels.
Changes in the microbiota of the recipient mice mirrored those in the donor mice, with clear differences between those receiving microbes from exercised and sedentary mice. There were also differences between the sedentary and exercise-inoculated mice in metabolite profiles, colon inflammation, and body mass in recipient mice five weeks after colonisation.
The mice that received the exercised microbiota showed greater resistance to experimental ulcerative colitis with less overall inflammation seen.
Humans were the subject of the second study, with their gut microbiota monitored as they moved from a sedentary lifestyle to a more active one. A mixture of lean and obese adults had their gut microbiomes analysed before they started a six week exercise program. The exercise was supervised aerobic activity for 30-60 minutes three times a week. Importantly, people were told to maintain their usual diet over the six weeks.
So how did the microbiome change after six weeks? The key outcome was a change in bacteria that produce a range of beneficial chemicals called short-chain fatty acids (SCFAs). SCFAs are important for gut health because they are the primary energy source for colonic cells and have anti-carcinogenic as well as anti-inflammatory properties.
SCFAs increased in the gut after the exercise program, but dropped after the program finished and people went back to a more sedentary life. There were also similar changes in the levels of bacteria that are known producers of SCFAs.
The most interesting finding was that positive changes were greatest in participants who were lean. These people had higher levels. Changes in SCFAs were much more modest in people who were obese. Obesity on its own is known to be linked to a less favourable diversity of bacteria so the finding here highlights the important role that exercise can play in helping to improve that.
Science is unravelling more information on how lifestyle can affect our gut microbiome and, in turn, influence our health. Exercise has many health benefits, and it seems from this new research that a potential benefit on the gut microbiome could be another one.