Exercise not only helps build stronger muscles but also fosters a healthier gut microbiome, with far-reaching benefits for gastrointestinal (GI) health and disease prevention, according to a comprehensive literature review.

Research has shown that physical activity enhances microbial diversity, boosts beneficial short-chain fatty acids such as butyrate, and strengthens the gut barrier. These shifts reduce inflammation and may guard against chronic conditions ranging from inflammatory bowel disease (IBD) to colorectal cancer (CRC).

“I think if clinicians were fully aware of the benefits of exercise for metabolic health in general, and gut health specifically, then they would be more inclined to recommend exercise programs as part of their treatment plans,” first author John Hawley, PhD, with the Mary MacKillop Institute for Health Research, Australian Catholic University in Melbourne, Australia, told Medscape Medical News.

“The problem here starts in medical school, where clinicians have only minimal exposure to both the massive evidence-based literature supporting exercise and dietary interventions for healthspan (as opposed to longevity),” Hawley said.

The review was published in the journal Gastroenterology.

The Muscle-Gut Axis

Recent research has revealed notable “crosstalk” between skeletal muscle and the gut microbiota, the authors noted.

Evidence has shown that contracting skeletal muscles release signaling molecules called “myokines” that communicate directly with the gut, which “boosts host immunity, facilitates a more diverse gut microbiome and functional metabolome, and plays a positive role in energy homeostasis and metabolic regulation,” they explained. 

In studies, moderate-to-vigorous physical activity has consistently correlated with a lower risk for metabolic liver disease, IBD, and irritable bowel syndrome (IBS). In patients with IBS, exercise has been shown to improve motility and ease symptoms, while in those with IBD, it can reduce inflammation and enhance quality of life, the authors noted.

For example, a recent systematic review and meta-analysis found that exercise improved IBD activity compared with controls.

In a separate study, a combination of exercise and psychological interventions in patients with Crohn’s disease led to positive changes in their intestinal microbiome, accompanied by reductions in systemic markers of inflammation. 

The protective effect of regular, moderate-to-vigorous physical activity on cancer risk has been well established, most notably for CRC, with regular exercise shown to cut CRC risk by as much as 40%. Exercise has also been shown to protect against CRC recurrence and improve survival.

Research has also shown greater gut microbiome diversity and differential abundances in CRC survivors who were physically active than in peers who were more sedentary.

Refining the Gut-Exercise Landscape

Despite the large interindividual variation in the human gut microbiome, reduced microbial diversity has been implicated in several GI tract diseases, systemic immune diseases, and cancers, the authors noted.

Accordingly, the gut microbiome has become an attractive target for modulating many of the positive effects of regular physical activity on GI health and disease. However, the precise dose of exercise required to improve GI health is currently unknown.

While moderate exercise strengthens gut health, prolonged intense training can temporarily increase gut permeability, causing symptoms such as cramping or diarrhea. These effects, however, are typically mild and reversible, research has shown.

“We need studies to define the precise dose and frequency of exercise required to promote favorable changes in the microbiome and enhance host immunity,” Hawley told Medscape Medical News. 

“This is essential because, unfortunately, the majority of the (lazy) population want a ‘quick fix’ for everything and will only be interested in the minimum requirements to induce these positive effects,” Hawley said.

Hawley believes novel targets uncovered by various “omics” technologies will “undoubtedly help refine the gut-exercise landscape and shape future interventions and treatment therapies.” 

“It is hoped that future therapies to treat a range of GI-related disorders, including cancers, will be based on a growing recognition that regular [physical activity] can positively modify the human gut microbiome, boost immunity, and decrease the incidence, progression, and personal burden of these noncommunicable diseases,” Hawley and colleagues wrote. 

"As such, it is recommended that regular physical activity be incorporated into standard clinical treatment protocols for individuals with several GI-related diseases,” they concluded. 

The Secret to a Healthy Gut

Targeting the gut microbiome for health through probiotics, diet, or fecal microbiota transplantation has the potential to enhance the protective effects of exercise against GI diseases.

The gut-brain-microbiome axis remains “an emerging field of study,” Aasma Shaukat, MD, MPH, gastroenterologist with NYU Langone Health and director of GI Outcomes Research, Gastroenterology at NYU Grossman School of Medicine, both in New York City, told Medscape Medical News.

“We’re learning more and more about this, and we need to because the microbial colonies are so diverse and we haven’t nailed it down yet,” said Shaukat, who wasn’t involved in the review. 

Physical activity is “clearly beneficial for the gut microbiome. It regulates the gut motility and also helps us kind of digest food in a way that the gut bacteria can actually feed on the good components and proliferate,” Shaukat said. 

In her own practice, Shaukat said she encourages patients to engage in regular physical activity, which can also boost mood and help relieve stress.

Eating well is also a key ingredient for gut health. 

“What we tell patients is to essentially increase their intake of gut-friendly foods that preferentially grow the bacterial colonies that are beneficial for us,” Shaukat said. This includes fermented foods, yogurt, kimchi, chia seeds, kombucha, pickled vegetables, and whole grains.

“By and large, a balanced Mediterranean diet and regular activity are truly the secret to gut health,” Shaukat said.

This research had no commercial funding. Hawley reported no relevant disclosures. Author Samuel C. Forster is a consultant to BiomeBank Australia and has served as an advisor to Microbiotica. Author Edward M. Giles is an advisor to AbbVie and Janssen and has received speaker fees from Takeda, Janssen, Nutricia, Aspen Nutritionals, AbbVie, Evolution Health, and H&H Group. Shaukat reported no relevant disclosures.