Diet, microbes & immune responses: dissecting the role of diet and the gut microbiome in intestinal inflammation and cancer immunotherapy

Chronic immune-mediated diseases and cancer are on the rise globally, partly due to the adoption of Western diets and lifestyles. Research increasingly shows that the gut microbiome, which is influenced by what we eat, plays a key role in regulating our immune system, metabolism, and response to medications. This PhD thesis investigates the link between diet, the gut microbiome, and its impact on inflammatory bowel disease (IBD) and cancer treatment.
The first part of the thesis examines the connection between diet, gut microbiome composition, and inflammation in both patients with IBD and the general population. It found that diets rich in vegetables, legumes, grains, fruits, nuts, and fish are associated with an increase in gut bacteria that produce anti-inflammatory compounds. Conversely, diets high in processed foods, sugar, meat, and fast food were linked to bacteria known to promote intestinal inflammation. These results suggest that dietary habits play a crucial role in gut health and inflammation.
The second part explores how diet and the gut microbiome affect cancer treatment, specifically immune checkpoint blockade (ICB) therapy. While ICB has revolutionized cancer care, it doesn't work for everyone. This PhD-research suggests that a Mediterranean diet could improve the effectiveness of ICB therapy, and that the gut microbiome plays a significant role in determining treatment effectiveness and potential side effects, such as intestinal inflammation.
Overall, the findings of this thesis highlight how the gut microbiome can be influenced by diet and its potential for improving treatment outcomes in both IBD and cancer.