Adhering to a Mediterranean diet lowers the risk of developing Crohn’s disease in middle age, a large Swedish study reports.
The study, “Adherence to a Mediterranean diet is associated with a lower risk of later-onset Crohn’s disease: results from two large prospective cohort studies,” was published in the journal Gut.
Inflammatory bowel disease (IBD) is caused partially by a deregulated immune response, with the human microbiome playing a role. In many cases, there are alterations in the in the natural community of microbes that populate our gut, leading to disease.
Dietary interventions in IBD are of interest because they can help ease symptoms without the risks associated with some medications.
Examples of diets include exclusive enteral nutrition (EEN), a dietary intervention in which patients receive a liquid diet of formula, either orally or via nasogastric tube, and the Crohn’s disease exclusion diet (CDED), which combines partial EN with a strict exclusion diet that avoids foods that may have negative effects on the gut microbiome.
“Nevertheless, prior epidemiologic studies of the relationship between diet and IBD have yielded very few plausible causal relationships,” the authors wrote. “The majority of these studies have focused on individual food groups and nutrients,” they stated, adding that studies focusing on overall diet patterns and the risk of IBD can yield more complex and reality-based conclusions.
In this study, researchers in the U.S. and Sweden investigated the link between adherence to a Mediterranean diet and risk of Crohn’s disease (CD) and ulcerative colitis (UC), the two main forms of IBD.
Mediterranean diet is rich in fruit, vegetables and whole grains, polyunsaturated fats (e.g., nuts, seeds, fish, seed oils), and proteins from fish, legumes and nuts. Evidence suggests that in countries where residents regularly consume a Mediterranean diet (southern Europe), there is lower incidence of IBD.
To evaluate the risk of both CD and UC in relation to the Mediterranean diet, researchers used two large prospective cohorts (groups): the Swedish Mammography cohort and the Cohort of Swedish Men.
Both groups comprised a total of 83,147 participants followed for an average of 17 years at baseline. Participants answered a 96-item semi-quantitative food frequency questionnaire (SFFQ) that measures frequency of intake and serving size of common food groups (fruit, vegetables, grains, fermented dairy products and fish, among others).
Researchers calculated a modified Mediterranean diet score (mMED), ranging from 0 to 8, in which increasing scores mean a broader adherence to the diet.
Researchers identified 164 cases of CD and 395 cases of UC, diagnosed from the ages of 47 to 83.
The results showed that a higher mMED score was associated with a significantly a lower risk of CD. However, no such link was seen for UC.
Because intake of fruit and vegetables could influence the risk for IBD, researchers recalculated mMED scores separating these two food groups. Participants with highest mMED (scores 7–8) still showed a lower risk for CD compared to individuals with the lowest scores (0–2).
No alterations to the link between Mediterranean diet and lower CD risk were found for other confounding factors, including dietary changes and rapeseed oil consumption.
Overall, “in two large prospective cohorts of middle-aged men and women in Sweden, we demonstrate that greater adherence to a Mediterranean diet is inversely associated with risk of later-onset CD but not UC,” researchers wrote.
“Our study further highlights the importance of continued research focusing on the benefits of the Mediterranean diet in patients with established CD,” the study concluded.