How Exercise Benefits the Digestive System

How Exercise Benefits the Digestive System

Exercise is the answer to many health-related questions. Want to lose weight? Exercise more. Want to maintain a healthy heart? Get exercising. Want to reduce your cholesterol? Well, you the message. One area where things aren’t quite as clear, however, is the digestive system. Does exercise benefit digestion, and if so what does it do that’s so welcome?

Changes to Gut Bacterial Colonies

Only a few decades ago we knew very little about the function of the gut, besides it’s obvious job in digesting the food we eat. In recent years, however, scientists have started to unravel the incredible relationship between the gut and general health. The funny thing is that the deeper experts dig, the more interactions they uncover, like the recent news that Parkinson’s disease may even start in the gut.

It shouldn’t come as any surprise that your gut is home to a complex and carefully balanced range of bacteria. Sometimes known as the “gut microbiome”, this is really the forefront of current science, with data suggesting that your gut bacteria may affect anything from lactose intolerance to eczema, from digestive issues such as constipation or diarrhoea to even premenstrual syndrome.

To be clear, however, many of these remain to be comprehensively and conclusively proven or even understood. The important message here is that those tiny microorganisms in your digestive system seem to do an awful lot more than just help you digest last night’s dinner. Better gut bacteria means better health for most of us.

Quite how exercise affects the gut bacteria was tested on a group of sedentary volunteers. They participated in an exercise program designed to slowly tax their bodies over a period of six weeks. Thereafter they were allowed to go back to their former sedentary lifestyle while monitoring of gut bacteria continued.

The scientists observed that “exercise training induces compositional and functional change in the human gut microbiota”. Perhaps just as interestingly, during the final phase where exercise was ceased, bacterial levels in the gut dropped back to their former levels, suggesting that ongoing exercise is important to maintain this beneficial boost.

Improved Gut Mobility

A healthy digestive system is one that moves food at a suitable rate - slow enough to absorb as many nutrients as possible, but fast enough that constipation does not ensue. Indeed, exercise has long been a recommended treatment for those suffering digestive complaints; what does the science tell us?

A simple experiment was carried out wherein volunteers were invited to consume a radio-isotope before completing a range of different exercises. The time it took for this “marker” to pass through the digestive system was then tracked, and compared with exercise method. Hardly surprisingly, the paper reports that “transit time was dramatically accelerated by moderate exercise”.

In other words, if you’re prone to digestive troubles then even a modest amount of exercise may help to stimulate optimal gut transit.

Control of Inflammatory Conditions

While inflammation has an important role to play in protecting the body, it can also be the source of many health conditions. Everything from rheumatoid arthritis to acne are believed to have an inflammatory element. Reducing inflammation has been shown time and again to help improve such situations.

There are a range of digestion-related conditions where experts believe that inflammation is central. Examples include Irritable Bowel Syndrome (IBS) and diverticulosis. Studies have found, however, that exercise can help to reduce inflammation, and thus to improve symptoms in many sufferers.  

One study claimed that even “single bouts of exercise have a potent anti-inflammatory influence”, theorising that it may be this anti-inflammatory influence that encourages beneficial growth of friendly gut bacteria.

Reduced Odds of Some Cancers

Possibly one of the most intriguing influences of exercise on the digestive system is the impact it can have on some cancers. According to Cancer Research UK, 42,042 new cases of colon cancer are diagnosed each year, with 54% of those being preventable. While there can be many contributing risk factors - such as the consumption of processed meat or a higher body fat content - exercise is considered to have an important role.

Cancer Research states that “5% of bowel cancer cases in the UK are caused by too little physical activity”. Other similarly sobering statistics come from a study of 17,148 people carried out at Harvard University. Completed over a 23 year period, the results showed that individuals who were “highly active... had half the risk of developing colon cancer relative to those who were inactive.”

In conclusion, regular exercise is therefore an important part of reducing the chances of tumours of the digestive system.

Immune Support

The digestive system is often overlooked as a barrier to infection from harmful viruses, bacteria and other pathogens. In reality, the gut is constantly bombarded by antigens both from the environment as well as the food we consume. Maintaining this barrier is therefore of great importance to promote good health, and there are two ways in which exercise can help.

To begin with, as previously discussed, exercise can boost the gut microbiome. These bacteria don’t just help with digestion, however; they also represent a source of immunity from infection. Friendly bacteria can help to stimulate the immune system of the gut lining, ensuring fuller protection.

Secondly, and just as importantly, exercise has been shown in studies to increase the proliferation of lymphocytes at various sites around the body including the gut wall. Lymphocytes are better known as a type of white blood cell, a crucial part of the immune system.

Important Caveat: Effects May Vary With Intensity Level

By now one could be forgiven for assuming that all exercise is good for the digestive system, however that isn’t necessarily the case.

Numerous studies have shown that while moderate levels of exercise can be highly beneficial for the gut, more intense programs can have quite the opposite effect. The results of one survey suggested that as many as 70% of serious athletes routinely suffer from problems such as heartburn, vomiting or diarrhoea.

While all forms of exercise can put the body under a degree of stress and increase harmful free radical production, the results of more modest exercise is easily handled by the body. More serious exercise, such as running a marathon, can create so much chemical stress that the body is simply unable to cope with the pressure. This, in turn, can lead to unpleasant digestive issues, even if they’re only temporary.  

Highly intense exercise may therefore actually suppress the immune system for example, or increase inflammation thanks to the greater release of reactive oxygen species.

Lastly, it should be noted that research suggests running to be far and away the most “extreme” form of exercise when it comes to digestive health. The odds of suffering unpleasant side effects are almost twice as high as for other endurance sports like cycling or swimming.


Sources:

https://www.theguardian.com/society/2019/jun/26/growing-evidence-suggests-parkinsons-disease-starts-in-gut
https://journals.sagepub.com/doi/abs/10.1258/mi.2009.009008
https://www.bmj.com/content/318/7189/999.short
https://journals.lww.com/co-clinicalnutrition/Abstract/2009/09000/The_impact_of_physical_exercise_on_the.13.aspx
https://gut.bmj.com/content/32/8/941.abstract
https://link.springer.com/article/10.1007/s00284-011-9915-3
https://www.cambridge.org/core/journals/proceedings-of-the-nutrition-society/article/diet-exercise-and-gut-mucosal-immunity/E5B64F96FB369CD7107A9535F0B5B21D
https://gut.bmj.com/content/48/3/435.short
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