Close up slide image of Crohn's colitis cells.


Crohn’s disease is an autoimmune disorder that affects more than a million Americans. It is an inflammatory bowel disease in which the body attacks the intestines. There is currently no known cure for Crohn’s disease; current research focuses on controlling symptoms. There is no definitive medical or surgical therapy.

The best we have is a plant-based diet, which has afforded the best relapse prevention to date.

Researchers got the idea to try a plant-based diet because diets rich in animal protein and animal fat have been found to cause a decrease in beneficial bacteria in the intestine. So, researchers designed a semi-vegetarian diet to counter that, and 100 percent of subjects stayed in remission the first year and 92 percent the second year. These results are far better than those obtained by current drugs, including new “biological agents” that can cost $40,000 a year, and can cause progressive multifocal leukoencephalopathy, a disabling and deadly brain disease. And a healthier diet appears to work better.

But what about preventing Crohn’s disease in the first place? A systematic review of the scientific literature on dietary intake and the risk of developing inflammatory bowel disease found that a high intake of fats and meat was associated with an increased risk of Crohn’s disease as well as ulcerative colitis, whereas high fiber and fruit intakes were associated with decreased risk of Crohn’s.

These results were supported more recently by the Harvard Nurse’s Health Study. Data revealed that long-term intake of dietary fiber, particularly from fruit, was associated with lower risk of Crohn’s disease. Women who fell into the highest long-term fiber consumption group had a 40 percent reduced risk, leading the accompanying editorial to conclude, “advocating for a high-fiber diet may ultimately reduce the incidence of Crohn’s disease.” 

The irony is that the highest fiber group wasn’t even eating the official recommended daily minimum of fiber intake.

Apparently, even just being less fiber deficient has a wide range of benefits, including a significant reduction in the risk of developing Crohn’s disease.

But why? The authors suggest it’s because “fiber plays a vital role in the maintenance of our intestinal barrier function.”

Our skin keeps the outside world outside, and so does the lining of our gut, but in Crohn’s disease, this barrier function is impaired. You can see this under an electron microscope as shown in my video Preventing Crohn’s Disease With Diet. The tight junctions between the intestinal cells have all sorts of little holes and breaks. The thought is that the increased prevalence of inflammatory bowel diseases may be due to dietary changes that lead to the breakdown of our intestinal barrier, potentially allowing the penetration of bacteria into our gut wall, which our body then attacks, triggering the inflammation.

Big vs. Small

We know fiber acts as a prebiotic in our colon (large intestine), feeding our good bacteria, but what does fiber do in our small intestine where Crohn’s often starts? We didn’t know, until a landmark study was published. Researchers wanted to find out what could stop Crohn’s associated invasive bacteria from tunneling into the gut wall. They found the invasion is inhibited by the presence of certain soluble plant fibers, such as from plantains and broccoli at the kinds of concentrations one might expect after eating them. They wondered if that may explain why plantain-loving populations have lower levels of inflammatory bowel disease. But, the researchers also found that there was something in processed foods that facilitated the invasion of the bacteria. Polysorbate 80 was one of them, found predominantly in ice cream, but also found in Crisco, Cool Whip, condiments, cottage cheese... just have to read the labels.

What about maltodextrin, which is found in artificial sweeteners like Splenda, snack foods, salad dressings, and fiber supplements? Maltodextrin markedly enhanced the ability of the bacteria to glob onto our intestinal cells, though other additives, carboxy-methyl cellulose and xanthan gum, appeared to have no adverse effects.

This may all help solve the mystery of the increasing prevalence of Crohn’s disease in developed nations, where we’re eating less fiber-containing whole plant foods and more processed foods. What we need now are interventional studies to see if boosting fiber intake and avoiding these food additives can be effective in preventing and treating Crohn’s disease. But until then, what do we tell people? The available evidence points to a diet low in animal fat, with lots of soluble fiber-containing plant foods, and avoiding processed fatty foods that contain these emulsifiers. We also want to make sure we’re not ingesting traces of dishwashing detergent, which could have the same effect; so, make sure to rinse your dishes well. Researchers found that some people wash dishes and then just leave them to dry without rinsing, which is probably not a good idea. We don’t currently have studies that show that avoiding polysorbate 80 and rinsing dishes well actually helps. Nevertheless, advice based on ‘best available evidence’ is better than no advice at all.

Here’s a video about using a more plant-based diet to reduce the risk of relapses: Dietary Treatment of Crohn’s Disease.

Photo credit: CROHN'S COLITIS euthman via / CC BY

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NUTRITIONFACTS.ORG is a strictly non-commercial, science-based public service provided by Dr. Michael Greger, providing free updates on the latest in nutrition research via bite-sized videos. There are more than a thousand videos on nearly every aspect of healthy eating, with new videos and articles uploaded every day. was launched with seed money and support by the Jesse & Julie Rasch Foundation. Incorporated as a 501c3 nonprofit charity, now relies on individual donors to keep the site alive.

Dr. Greger is a physician, New York Times bestselling author, and internationally recognized speaker on nutrition, food safety, and public health issues. A founding member and Fellow of the American College of Lifestyle Medicine, Dr. Greger is licensed as a general practitioner specializing in clinical nutrition. Currently he proudly serves as the public health director at the Humane Society of the United States. Dr. Greger is a graduate of the Cornell University School of Agriculture and the Tufts University School of Medicine.

His latest book, How Not to Die, became an instant New York Times Best Seller. 100% of all proceeds he has ever received from his books, DVDs, and speaking engagements has always and will always be donated to charity. Dr. Greger receives no compensation for his work on

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