When it comes to eating plans, the Mediterranean diet in particular has been linked to a reduced risk of heart disease, lower cancer risk, and protection against type 2 diabetes, Alzheimer’s, and chronic inflammatory diseases. Now a new investigation suggests that middle-aged people may dramatically lower their chances of developing Crohn’s, an inflammatory bowel disease (IBD) that causes inflammation in the digestive tract, by following this eating plan. A study published January 2020 in the journal Gut found that individuals who adhered to a Mediterranean diet had a 60 percent reduced risk of developing Crohn’s disease. “Diet is widely thought to play an important role in both development and progression of inflammatory bowel diseases,” says the lead investigator, Hamed Khalili, MD, MPH, a gastroenterologist with Massachusetts General Hospital in Boston. “Many of the components of this diet — including olive oil, fruits, vegetables, and nuts — have a strong anti-inflammatory effect.” RELATED: 8 Scientific Health Benefits of the Mediterranean Diet
The Greater the Adherence, the Better the Outcomes
Dr. Khalili and his coauthors based their conclusions on a large Swedish population of 83,147 individuals who ranged in age from 45 to 79. They were either women from the Swedish Mammography Cohort or men from the Cohort of Swedish Men, and they self-reported their eating habits via questionnaire. Over the course of 20 years, between 1997 and 2007, 164 cases of Crohn’s disease and 395 cases of ulcerative colitis, or UC (another common type of IBD that affects the innermost lining of the large intestine and rectum), were confirmed. Scientists observed that a higher adherence to a Mediterranean diet corresponded with a lower risk of Crohn’s disease. They estimated that sticking to a Mediterranean diet could have prevented around 12 percent of the Crohn’s disease cases. The Crohn’s & Colitis Foundation of America estimates that about 780,000 Americans currently have Crohn’s (907,000 currently have UC). For Sidhartha Sinha, MD, a gastroenterologist with Stanford Health Care in California, who was not involved in the study, the results were not surprising. “The Mediterranean diet is a common approach recommended to patients with IBD, and many of us have personal experiences of patients seemingly benefiting from such a diet,” he says. “However, what is also more clear is that just as with medical therapies, there may not be a ‘one size fits all’ diet for all patients with IBD.”
Zero Benefit Seen for Ulcerative Colitis
In contrast to Crohn’s, UC risk did not seem to improve for those individuals who kept to a Mediterranean eating plan. Khalili believes the gut microbiome likely plays a stronger role in the development of Crohn’s disease, and that the inflammation associated with the illness responds better to dietary modifications. “Crohn’s and UC are different diseases affecting different parts of the gastrointestinal tract with often very different presentations,” says Dr. Sinha. “The role of intestinal microbes in each part of the gut affected by disease or by intervention may have varying results.” The study authors note that high-fiber grains and legumes, which are part of a Mediterranean-style eating plan, may play an important role. Research has identified fiber intake as protective against Crohn’s. Optimal fiber intake may vary from case to case, though. For people with Crohn’s, the Crohn’s & Colitis Foundation says that limiting fiber can help reduce both cramping and bowel movements. That means avoiding green leafy vegetables, nuts, seeds, whole grains, and raw fruits with peels. “Fiber appears to be protective in maintaining a healthy intestinal barrier and microbiome, but high fiber is also not the correct choice for all patients,” says Sinha. The scientists in this investigation stress that the study is observational, and other factors they did not evaluate may account for the findings. They also only assessed diet at baseline and therefore could not account for changes in diet over the follow-up period. In addition, results came from a largely homogeneous Swedish population, so they may not apply to other ethnic groups or populations in other geographic locations. To date, we do not have definitive evidence consistently showing that any particular oral diet is beneficial for adults with IBD in prospective randomized controlled trials, according to Sinha. “This study does offer hope that a Mediterranean diet may be beneficial but does not reduce the need for prospective randomized studies,” he says. For Khalili, the next step is to examine whether the Mediterranean diet also has beneficial effects in patients with established Crohn’s disease.
