As the saying goes, an apple a day keeps the doctor away, but figuring out exactly how long-term dietary patterns affect the gut microbiome’s role in regulating inflammation has not been quite as clear for researchers.

Diet has been shown to play a role in both IBD and IBS symptoms and possibly disease progression

Although diet is one of the most important factors that shapes gut microbiota composition, current studies have been limited to focusing on single nutrients or food components rather than the role a person’s entire diet plays in health and disease.

Diet has been shown to play a role in both IBD and IBS symptoms and possibly disease progression. For example, a diet high in foods that have a high inflammatory score, such as processed meat, sugar and refined grains, has been associated with Crohn’s risk. On the other hand, other dietary recommendations have been made for managing IBS, such as following a low FODMAP diet and avoiding specific trigger foods, but long-term avoidance of high-fiber foods could have detrimental effects on the gut microbiome. Despite these findings, the interaction between diet, gut microbiota composition and the role intestinal microbes play in inflammation and disease is still greatly unknown.

For this reason, researchers from the University of Groningen and University Medical Centre Groningen in the Netherlands aimed to uncover the interaction between long-term dietary patterns, specific nutrients and the gut microbiota in 1,425 individuals by analyzing fecal samples and food questionnaires. The participants came from four different cohorts that included IBD patients, IBS patients, and healthy subjects.

The researchers identified 38 associations between dietary patterns and microbial clusters, and diet-gut microbiome associations were consistent in IBD and IBS patients as well as the general population. Most importantly, the authors of the study showed that dietary patterns as a whole are more important for overall gut health than focusing on specific nutrients.

For example, in agreement with another recent study, a diet high in bread, legumes, cereals, fruits, vegetables, nuts and fish, which are all traditionally present in significant amounts in the Mediterranean diet, was associated with lower amounts of inflammatory bacteria and higher abundances of short chain fatty acid (SCFA)-producing bacteria such as Faecalibacterium, which have anti-inflammatory properties and can support proper intestinal barrier function.

Unsurprisingly, following a Western diet, which is characterized by regularly consuming fast food, sugar, soda and processed meat, correlated with higher amounts of bacteria that have been associated with immune-mediated inflammatory diseases and erosion of the intestinal barrier.

Total fat and meat intake was also associated with bacteria normally found in the mouth and upper gastrointestinal tract that have been linked to diseases such as IBD, colorectal cancer and liver cirrhosis. The authors postulated that this could be because a high-fat diet may increase the pH in the colon, which facilitates the growth of non-beneficial bacteria, compared to a plant-based diet that creates a more acidic environment in the colon that supports the growth of more anti-inflammatory SCFA-producing bacteria.

Although this was a cross-sectional study, and therefore the cause of the association between diet and gut microbiota composition cannot be identified, the study does further support previous research that certain dietary patterns consistently correlate with specific groups of bacteria that affect inflammation status in IBD, IBS and healthy individuals.

Certain dietary patterns consistently correlate with specific groups of bacteria that affect inflammation status in IBD, IBS and healthy individuals

To summarize, while it may be tempting to adopt a trendy diet or think that one food component can make or break your diet, the evidence does not support this. Recent studies have illustrated that adopting a plant-based Mediterranean diet is best for gut health and for reducing intestinal inflammation due to its high fiber, polyphenol and omega 3 fatty acid content, which leads to higher amounts of SCFA-producing bacteria that have anti-inflammatory properties and support a healthy gut barrier.

The study paves the way for future long-term analysis to be conducted in order to better understand the relationship between diet, gut microbiome composition and disease.




Bolte LA, Vich Vila A, Imhann F, et al. Long-term dietary patterns are associated with pro-inflammatory and anti-inflammatory features of the gut microbiome. Gut 2021;70:1287-1298.