Anticancer treatments, including chemotherapy and radiotherapy, indirectly or directly reduce gut barrier function, leading to gastrointestinal illnesses, nutrient malabsorption, endotoxemia and chronic low‐grade systemic inflammation. While exercise is promoted as part of the cancer treatment plan, as well as for cancer survivors, there is little evidence on the impact of different exercise intensities on gut barrier function.

Aim: The aim of this study was to investigate the effects of a cycling‐based exercise intervention on circulating gut‐permeability biomarkers in breast cancer survivors.

Methods: Female participants (n = 17; age 63 years, BMI: 26.3 ± 44 kg/m2) were randomised for a 12 week supervised exercise intervention: (a) high intensity interval training (HIIT) group (n = 6); (b) moderate‐intensity continuous exercise (MOD) group (n = 5); or (c) control with no exercise (CON) group (n = 6). Blood samples were drawn pre‐ and post‐intervention to test circulatory intestinal fatty acid‐binding protein (i‐FABP) and lipopolysaccharide‐binding protein (LBP).

Results: There were small decreases in i‐FABP and LBP after the 12‐week HIIT intervention (−15.6 ± 8.1%; −0.55 ± 0.31%, small), with trivial and unclear changes for CON and MOD between pre‐ and post‐interventions.

Conclusion: i‐FABP is a marker of intestinal mucosal damage, while LBP is an acute‐phase protein that binds to bacterial lipopolysaccharide (LPS) from the gut to initiate an immune response to the LPS. The small reduction in these two markers in the HIIT group suggests improved gut barrier function in breast cancer survivors after 12‐weeks of training, potentially reducing the health complications relating to gut permeability. These results and the mechanisms underlying the potential benefits of HIIT for gut barrier function need to be explored further in larger studies.