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Nutrition

Nutritional Pearls: Could A Mediterranean Diet Help Reduce Crohn Disease Risk?

  • Answer: While there is little research available into diet-related prevention of Crohn disease, it is plausible that an anti-inflammatory diet could confer some protection against inflammatory conditions.

    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 disease is exclusive enteral nutrition (EEN), in which patients consume 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. Today, we’ll look at an 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 disease or ulcerative colitis (UC)?

    The Research

    The authors utilized data gathered for 2 long-term, large-scale studies carried out in Sweden. The first study was the Swedish Mammography Cohort, which recruited participants between 1987 and 1990. At the start, over 66,000 women aged 40 to 74 years responded to written surveys on height and weight, lifestyle factors, health history, and dietary intake. The second study was the Cohort of Swedish Men. It included over 45,000 men aged 45 to 79 years and also began in 1987. The men responded to written surveys on diet, 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 who responded to both the initial survey and 1997 survey and who were also free of inflammatory bowel disease at baseline.

    Using the dietary questionnaires, 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 grouped into 5 levels: 0-2 points, 3-4 points, 5 points, and 6-8 points.

    The Results

    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 disease.

    Even more interesting is that those with a score of 5 were 22% less likely to develop Crohn disease, and those with a score of just 3-4 were 30% less likely to develop Crohn disease. 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 the participants’ Mediterranean diet score. They noted that those 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 disease, but these associations did not all rise to the level of statistical significance.

    What’s the Take Home?

    As with all observational studies, this can only show association and not causation. However, 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 disease.

    Reference:

    Khalili H, Hakansson N, Chan SS, et al. Adherence to a Mediterranean diet is associated with a lower risk of later-onset Crohn’s disease: results from two large prospective cohort studies. Published online January 3, 2020. Gut. doi: 10.1136/gutjnl-2019-319505