Can a disrupted gut microbiome weaken your immune system?

Around 70 to 80 percent of all immune cells in your body are located in your gut. Your gut microbiome works closely together with the immune system in your gut wall and also influences immune responses elsewhere in your body. A healthy, diverse gut microbiome is needed for the normal development and regulation of your immune system, both locally and throughout the body¹.

When your gut microbiome becomes unbalanced, a condition called dysbiosis, your immune system can be thrown into disarray. This increases the risk of chronic inflammatory diseases. Review studies also link dysbiosis to a higher likelihood of cardiovascular disease and cancer, although for these conditions the cause-and-effect relationship has not been proven in every case²,³.

Your gut microbiome also appears to influence how well cancer patients respond to immunotherapy, specifically to so-called immune checkpoint inhibitors. This relationship has been described in multiple studies, but the precise mechanism is still being investigated. Doctors do not yet routinely act on this in clinical practice⁴,⁵,⁶.

For those who want to support their gut microbiome, fermented foods offer the strongest evidence base. In a 17-week study of 36 healthy adults, microbiome diversity increased and inflammatory markers in the blood decreased in people who consistently ate more yogurt, kefir and fermented vegetables⁷. A high-fiber diet did not show a clear or consistent immune effect: the effect depended strongly on each person's existing gut microbiome composition. Fiber is still healthy for other reasons.

Finally, your immune system also appears to form a bridge between the gut and the brain. Disruptions in the gut microbiome have been linked to inflammation in the brain and possibly to psychiatric and neurological conditions. This field of research is still in its early stages and the associations have not yet been proven to be causal⁸.