Mairlyn Smith, actress and cook, recently revealed on TikTok that she and her husband go for a walk after dinner to release their pent up gases. Smith calls these strolls “fart walks”. The hashtag is now blowing up on social media, writes health lecturer Dan Baumgardt.
The purpose of a fart walk is to start the digestive process and relieve bloating, troublesome gas or the sensation of a big meal sitting in your stomach like a brick. Smith claims that a ten- to 20-minute stroll, helps you “age wonderfully”.
But does science back up the benefits of an after-meal stroll? And how might our knowledge of digestive function and illness contribute to finding ways to shed that bloated feeling with exercise?
First, consider what happens when your stomach is filled following a good meal. Its capacity varies according to age, size and eating habits, but fill it up and, like a washing machine, it starts to churn.
The autonomic nervous system controls movement and activity in your heart, lungs and guts. It is an automatic system that operates beyond your conscious control. You don’t think about making your heart beat or your bowels move for instance, do you?
There are two divisions of the autonomic system. The sympathetic division commands fight-and-flight responses, such as increasing heart rate and blood pressure. This allows you to either stand your ground or run like the clappers.
Its opposite is the parasympathetic nervous system, which governs rest-and-digest responses. This comes into play when you’re ready to reduce that chewed-up meal into soup (also called chyme) and absorb all its nutrition into the bloodstream. Then excrete the waste and gases as faeces and flatulence.
To do this, the parasympathetic nervous system mobilises your gut. It causes the release of digestive juices, containing enzymes that break down carbohydrates, fats and proteins into smaller absorbable molecules. It also activates the muscle in the gut wall, allowing the chyme to move along. This waveform of action is called peristalsis.
Where do farts come from?
This is a question my daughter asked me a couple of weeks ago. When I started explaining bacteria and fibre fermentation she lost interest and asked if she could watch Bluey instead.
It may well have been where she got the question from in the first place. Flatulence is the symptom associated with flatus – the accumulation of gas within the digestive tract. There are many ways gas can build up, and diet is often a big culprit.
High-fibre foods and those with indigestible carbohydrates, such as inulin, (Jerusalem artichokes being a prime example) remain in the gut where its bacteria induce fermentation. Those who’ve attempted the high-fibre cabbage soup diet might also be able to attest to it. Don’t forget the flatulent power of fizzy drinks either, nor the swallowing of air that can occur when eating too quickly.
While flatulence is a normal part of life, excessive frequency (or odour) can be a sign of a gastrointestinal disorder. These include gluten or dairy intolerance, or irritable bowel syndrome.
So what evidence is there that walking can aid digestion?
The results obtained from investigating the effect of exercise on the gut are somewhat inconsistent. There are several gastrointestinal symptoms to consider. In the case of constipation, eating fibre is a good measure, but regular exercise is advised as having a positive effect on bowel movements. And it doesn’t need to be ultra-marathons or pumping iron for three hours. Regular walking or light running is often recommended.
A review of studies showed positive effects of aerobic exercise and qigong (Chinese movement exercises similar to tai chi), but concluded that more rigorous research was needed to investigate further. In fact, moderate daily exercise has been associated with a reduced risk of developing bowel cancer and diverticular disease (development of small pouches of the bowel), which have associations with constipation.
What about flatulence?
One study found that gut symptoms, chiefly passing gas, were more prominent and frequent at rest than during exercise. Another examined the effect of exercise levels on symptoms like flatulence and nausea. They found that long-distance walking (that is, low-intensity, prolonged exercise) generated these symptoms, though with notably less frequency and severity when compared with high-intensity exertion.
So is it possible to overdo it? Gastrointestinal symptoms are frequently reported in athletes – runner’s trots, for instance. These relate to episodes of diarrhoea runners may experience during a race.
As well as diarrhoea, heavy exertion may also cause symptoms of indigestion, nausea and abdominal pain as a result of reduced blood supply to the gut as it gets redirected to the muscles – an example of the sympathetic system working against digestion.
What are the other mechanisms for the influence of exercise on the gut then? Other suggestions are that sympathetic action and the cascade of different hormones released during exercise cause localised inflammation in sections of the intestine. This might have the ability to change the gut microbiome and therefore flatus production.
So, while the jury is out on a clear-cut answer and recommendation, it isn’t unreasonable to consider a trial of light exercise like walking to see if it can alleviate the earth, wind and fire in your abdomen. Its proven positive effects on other aspects of your health, such as cardiovascular risk and weight loss will be a bonus.
This article was written by Dan Baumgardt, Senior Lecturer, School of Physiology, Pharmacology and Neuroscience, University of Bristol, for The Conversation
