Mediterranean diet helps reduce your risk of Crohn’s

Crohn's disease is an autoimmune disorder, that along with with Ulcerative Colitis, is a subtype of Inflammatory Bowel Disease. Inflammatory Bowel Disease is characterized by long-term inflammation of portions of the gastro-intestinal tract: those with Crohn's may have inflammation anywhere from the mouth to the rectum, with healthy sections of gut in between the inflamed areas, and those with Ulcerative Colitis have their inflammation limited to the length of the large intestine.

Inflammatory Bowel Disease is a challenge because there is very little good research into diet-related treatment. Often medications are prescribed that can help with the inflammation or suppress the immune response, and patients are given diet-related advice ranging from a high-fiber diet to a "low-residue diet" - and if that sounds like a low-fiber diet, you're right. Another possibility is a low-FODMAP diet.

Perhaps the most effective treatment that we have right now for Crohn's disease is exclusive enteral nutrition (EEN), in which patients are fed a completely liquid diet. The problem, of course, is that this is a pretty drastic solution, and people like to eat real food.

If there's little good research into treatment, there's just as little into prevention. In today's Health & Nutrition Bite (Gut 2020;0:108 http://dx.doi.org/10.1136/gutjnl-2019-319505) we have analysis of a prospective, observational study of dietary habits and later development of Inflammatory Bowel Disease that specifically looks at a Mediterranean-style dietary pattern.

We know that a Mediterranean-style diet can help reduce certain markers of inflammation - might that anti-inflammatory diet help prevent Inflammatory Bowel Disease or its subtypes, Crohn's disease or Ulcerative Colitis (UC)?

The authors utilized data gathered for two long-term, large-scale studies carried out in Sweden: first, the Swedish Mammography Cohort, which recruited participants between 1987 and 1990. At the start over 66,000 women between the ages of 40 and 74 responded to written surveys on height and weight, lifestyle factors such as smoking status and physical activity, health history, and dietary intake.

The second study was known as the Cohort of Swedish Men and included over 45,000 men, also beginning in 1987 and including men between the ages of 45 and 79. The men also responded to written surveys on diet, health and health history, and lifestyle. For both groups, follow-up questionnaires were administered in 1997, 2008, and 2009. The diet records were validated for both cohorts by carrying out in-person dietary recall interviews of a subset of participants.

For their analysis the authors used only the data from participants in both groups who responded to both the initial and 1997 surveys who were also free of Inflammatory Bowel Disease at baseline.

With the dietary questionnaires the participants submitted, the authors were able to calculate a modified Mediterranean diet score for each participant on a scale of 0 to 8, with 8 being high adherence to a Mediterranean-style diet. Their score was then ranked into 5 levels: 0-2 points, 3-4 points, 5 points, and 6-8 points.

After taking into account gender, age, Body Mass Index, education, caloric intake, and smoking status, the authors found that compared to those with 0-2 points in their Mediterranean Diet score, those with a score of 6-8 were 58% less likely to develop Crohn's disease.

Even more interesting is that those with a score of 5 were 22% less likely to develop Crohn's, and those with a score of just 3-4 were 30% less likely to develop Crohn's. The authors calculated that every single-point increase in a participant's Mediterranean diet score reduced their risk by 13%.

Unfortunately, they could find no statistically significant association between overall diet and risk of Ulcerative Colitis.

In some exploratory analyses, the authors looked at specific components of their Mediterranean diet score. They noted that those participants who consumed more than the average amount of nuts and legumes, fruits and vegetables, unrefined grains, olive oil, and fermented dairy were slightly less likely to develop Crohn's, but these associations did not all rise to the level of statistical significance.

What this means for you

As with all observational studies, this can only show association and not causation. It's certainly plausible that an anti-inflammatory diet such as a Mediterranean-style diet could confer some protection against inflammatory conditions such as Crohn's. Here's more on an anti-inflammatory diet.

First posted: March 4, 2020