Preventing Ulcerative Colitis with Diet

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How to Prevent Ulcerative Colitis with Diet

What has driven the dramatic increase in prevalence of the inflammatory bowel disease Crohn’s disease in societies that rapidly westernized—a disease practically unknown just a century ago? What has changed in our internal and external environment that has led to the appearance of this horrible disease?

Japan suffered one of the most dramatic increases, and out of all the changing dietary components, animal protein appeared to be the strongest factor. There was an exponential increase in newly diagnosed Crohn’s patients and daily animal protein intake, whereas the greater the vegetable protein, the fewer the cases of Crohn’s, which is consistent with data showing a more plant-based diet may be successful in both preventing and treating Crohn’s disease (See Preventing Crohn’s Disease With Diet and Dietary Treatment of Crohn’s Disease). But what about other inflammatory bowel diseases?

In the largest study of its kind, shown in my video Preventing Ulcerative Colitis with Diet, 60,000 people were followed for more than a decade. Researchers found that high total protein intake—specifically animal protein—was associated with a significantly increased risk of the other big inflammatory bowel disease, ulcerative colitis. It wasn’t just protein in general, but the “association between high protein intake and inflammatory bowel disease risk was restricted to animal protein.” Since World War II, animal protein intake has increased not only in Japan but also in all developed countries. This increase in animal protein consumption is thought to explain some of the increased incidence of inflammatory bowel disease in the second half of the 20th century.

Other studies found this as well, but why? What’s the difference between animal protein and plant protein? Animal proteins tend to have more sulfur containing amino acids like methionine, which bacteria in our gut can turn into the toxic rotten egg smell gas, hydrogen sulfide. Emerging evidence suggests that sulfur compounds may play a role in the development of ulcerative colitis, a chronic inflammatory disease of the colon and rectum characterized by bloody diarrhea.

The first hint as to the importance of our gut flora was in the 1970’s when “analysis of stools showed that their bulk was made up of mostly bacteria, not undigested material.” We’re pushing out trillions of bacteria a day and they just keep multiplying and multiplying. They do wonderful things for us like create the protective compound, butyrate, from the fiber we eat, but unfortunately, the bacteria may also elaborate toxic products from food residues, such as hydrogen sulfide, “in response to a high-meat diet.”

Hydrogen sulfide is a bacterially derived cell poison that has been implicated in ulcerative colitis. We had always assumed that sulfide generation in the colon is driven by dietary components such as sulfur-containing amino acids, but we didn’t know for sure until a study from Cambridge was published. Researchers had folks eat five different diets each with escalating meat contents from vegetarian all the way up to a steak each day. They found that the more meat one ate, the more sulfide; ten times more meat meant ten times more sulfide. They concluded that “dietary protein from meat is an important substrate for sulfide generation by bacteria in the human large intestine.”

Hydrogen sulfide can then act as a free radical and damage our DNA at concentrations way below what our poor colon lining is exposed to on a routine basis, which may help explain why diets higher in meat and lower in fiber may produce so-called “fecal water” that causes about twice as much DNA damage. Fecal water is like when researchers make a tea from someone’s stool.

The biology of sulfur in the human gut has escaped serious attention until recently. Previously, it was just thought of as the rotten egg smell in malodorous gas, but the increase in sulfur compounds in response to a supplement of animal protein is not only of interest in the field of flatology—that is, the formal study of farts—but may also be of importance in the development of ulcerative colitis.

I have several videos on our microbiome, including:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

49 responses to “How to Prevent Ulcerative Colitis with Diet

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  1. I know so many people that just refuse to believe this. Its like Trump denying Climate change with all the scientific research done on the subject. Keep up the good work Dr. Greger. Thank you

    1. I really don’t want to play devil’s advocate but I have to correct you. Trump denies man made climate change but I see the confusion especially since the left has abandoned man made global warming for the euphemism of climate change and the president elect choosing his wording by that definition confuses people such as yourself. Nobody denies climate change. The climate is always changing hence the little ice age of the 18th century and the warming period we have now entered into in recent decades. The polluting industries which Trump supports is a different matter entirely. Carbon, one of the essential elements of life, not being one of the pollutants.

      1. Fair enough. Perhaps you are confusing Mr Trumps thoughts on clean coal as opposed to carbon that is necessary for life. Kind of a double edged sword. To me it is still Global warming. I’m not confused. When the temperature increases, that means warmer not colder. The left can call it anything they like.

        BTW, you can bet Trump has a filet mignon or some other fine cut of beef most evenings which would indicate he doesn’t read much of Gregers research either.

  2. So animal derived Hydrogen sulfide is bad. But vegetable derived sulfides are good? Like Brassicas – cabbage, broccoli, cauliflower and Alliums – onions, shallots, garlic, leeks.

    1. From what I have been able to find on a cursory glance around the net, the sulphur compounds in plants are different, that is, not hydrogen sulfide but other sulphurous molecules. I was going to list some, but there are several that have been studied, and some of the names are rather long, and I have to finish my wfpb breafast and get to work. So I guess there’s sulphur, and then there’s sulphur … and the plant kinds really are good for us.

    1. miki: Yes, fish protein is animal protein. Meat, dairy and egg products are all animal protein. (Unless we are talking about some product that pulls out only the fat, say something like butter. In that case, we are talking about animal fat…)
      Here is a nice NutritionFacts overview of fish:

  3. Dr. Greger, can you explain why some very young people get ulcerative colitis or Crohn’s disease? It seams that a 13 year old hasn’t had a long enough history with poor eating habits. Is it possibly an inherited gene or trait?

    1. Very good question BettyJaneC, I would like to know also. I hear of young people in their teens and early twenties afflicted with Crohn’s. And why them? Seems to me there must be other factors that come into play. I found this video (linked in the above article) just amazing. It affirms for me the incredible power of eating plant based. Positive, uplifting, and applicable to our own lives.. thank you once again Dr Greger.

      1. The answer also lies in animal protein -transported along with: mycobacterium avium paratuberculosis.
        Just as an allergy is developed, there is an an early exposure (dairy, even formula) then a later repeated ‘insult’ which triggers the disease process. Genetic susceptibility places a role.

        1. Thanks for the explanation ToBeAlive! So its several factors coming together for the perfect storm so to speak. What a devastating disease. Given the results of the trials with plant base diets being an overwhelming success, I would imagine that it has been established as protocol for management of this and ulcerative colitis. Though I can think of one person who suffers UC and is a meat eater.. think I’ll pass the links on!

            1. Thanks ToBeAlive! I was reading at the Crohn’s & Colitis Foundation this afternoon thìnking how might the microbiome figure into all of this. Its so exciting .. and they say it may impact other autoimmune diseases! The landscape of the field of medicine is changing.. we might not even recognize it in another few decades. And that could be a good thing.

      2. Because, I sincerely, believe , there is no black and white. Methionine in muscle meat of af any animal, fish included, in absence of fat, other tissues , organ meats and bones can be very problematic. Older traditional cultures never packed on muscle meat to the extend it is happening now. So the devil as always in details.
        Meat, as we know it now, never existed in such abundance and quality. Neither it was consumed in such quantities . Please, understand, I am not advocating for anything but balance in mind and body – whatever that means for every single individual. And our diseases do not always happen because we ate wrongly or behaved weirdly… So the healing is not always proper diet, and all other great things we all know about.

      3. Although I have no argument with the information re nutrition, Crohn’s Disease also has a genetic factor. I was diagnosed in my 30s. My niece’s daughter was diagnosed with Crohn’s when she was about six years old. She is now 14 & is on a biologic med. I also have psoriasis & psoriatic arthritis. A connection, autoimmune-wise? My guess is that there is.

    2. I would guess for the same reason little kids get cancer and diabetes, etc., both an environmental (dietary?) and genetic component. As they say, genetics loads the gun, but environment pulls the trigger.

    3. Two of my three kids by my first marriage suffered ulcerative colitis aged 11 and 13 and both had surgery for stoma and then in later teens had the reversal. Devastating for kids! The consultant said there was no proof of it being an heriditary condition but, strangely, did say it can run in families. I divorced from my wife between the two kids diagnoses and remarried some years later and now have two daughters, age 17 and 21, that have no bowel disease. What can be made of that if anything?


    4. I have seen how abominable some kids diets are (and how terrible their parents are for providing it to them) and I am surprised some of them even make it to their teens. So I am not surprised that with 10+ years of relentless daily dietary insults that even teenagers can develop conditions like this.

  4. As an RN I have a very basic thought on this is of sulphuric byproducts – the more anything smells bad from and in the human body, it means, “pay attention”. The body is very clear in its responses to what we eat, drink and breathe. As a matter of a fact, smell was predominantly used as a diagnostic tool just a few centuries ago.

    To that point, I have noticed that I no longer have putrid smelling stools or gas since eating a WFPBD and that tells me that that my body is not dealing with purification- what a relief! Sorry if anyone takes offense to the nature of my comment but when discussing the colon and digestion, it goes with it.

    1. No offense taken, especially after just scooping my carnivore’s litter box! Yuk!
      On a related note, anyone who imagines we are biologically carnivorous has obviously not paid attention to or seen the single minded focus, speed, agility and spectrum of amazing physical and behavioral adaptations of a TRUE carnivore! I have a couple of lazy cats and a 3 month old kitten, who despite my reservations, has been hunting the lizards, frogs, and and giant palmetto bugs that sneak into the lanai, and preventing them from coming into the house, now that we can rest the AC and leave doors and windows open. I figure he is to be commended not just for his exceptional natural hunting skills, but also for his contribution to pest control and supplementing his diet…though having him often come to me to “generously” share his bounty is a bit off putting! Sure beats what the “official” prescription is for our invasion of Cuban frogs (and anoles) that are devouring our native species…catch them, apply a 1-inch stripe of benzocaine ointment along the back of the frog until it’s unconscious and stick him in your freezer overnight! I kid you not! No thanks, sorry!

  5. I suffer from colitis and the only diet that I noticed immediate help me was the GAPS diet. This is basically the Paleo diet. My symptoms cleared up within a week and I was on the diet symptom free for about 1 year. I decided to say screw my colitis due to my compassion for animals and am now 100% on a plant based diet. My symptoms (Diarrhea) are there with the Plant Based Diet. Not with the Paleo diet though. My thought for why the Paleo diet fixed my gut issues was because meat is primarily digested in the stomach by hydrocloric acid and bile where as plant based diet foods are primarily digested in the small intestine. With a colitis ridden intestine, it makes sence to me why meat digested mostly by the stomach would alleviate symptoms.

    1. Hi Steven,
      While I’m not sure why you are symptom-free on Paleo, but not on a plant-based diet, I do not think it is due to your theory on how things digest in our system. Your idea definitely seems plausible however that is not actually how digestion works.

      Whole foods (meat vs plants) are NOT digested as entirely separate entities in separate places as you speculate. Each stage of the digestive process works on ALL foods to break them down both mechanically through physical processes like chewing and churning (of the stomach) as well as biochemical breakdown from acid (in the stomach) to enzymes in the saliva, stomach and intestines.

      So, in other words, meat isn’t ONLY ‘digested’ in the stomach and plant foods aren’t PRIMARILY digested in the small intestine. Each of these whole foods are broken down into their components-fats, carbs and proteins. And these macronutrients are then broken down into their subcomponents. All of the nutrients are targeted in all stages of the digestive tract by enzymes, in addition to the HCL in the stomach. Through the repeated stages and cycle of digestion each foods is broken down into macronutrients and other components and these broken down into their smallest molecules (for the macronutrients–fat, carbs, protein, they are broken into smaller fatty acids, amino acids, glucose, etc.)

      The fat in any food can be attacked first biochemically thru lipases (fat breakdown enzymes in our saliva) in our mouth. Chewing in the mouth and churning in the stomach will help to mechanically break down the fat and the acid will further help in the stomach, but then once in the intestine, the bile is released to help digest the fat their, too, as well as more lipase. Protein from meat is pulverized by the teeth and with the churning of the stomach, proteases at different stages including in the intestines also help breakdown to release smaller amino acids, and so on. Plant foods are broken down in the same way.

      It might be that your symptoms caused on a plant-based diet could be due to some entirely other factor. Perhaps a reaction to a specific food or a component of a food? Perhaps a reaction to excess fiber of some specific type? While you might eat the same plant foods on a paleo and a plant-based diet, perhaps their are some that you eat only when PB and not paleo? Or perhaps the quantities differ, and it might be a that you have a certain tolerance for low amounts of, say, gluten (could be anything) while on Paleo, but you increase the amount on PB and that level then becomes aggravating..? OR it could be something else altogether. Perhaps the Fodmap approach may help you identify some symptom triggers. Check this out: Keep your investigative mind open because it might be that you are able to identify a culprit. – nutrition professor and volunteer moderator, ‪ Martica Heaner, PhD‬‬‬‬

    2. There are multiple types of colitis with, it is thought, varying causes.

      However, as far as ulcerative colitis is concerned, there is quite good evidence that red meat and alcohol consumption are risk factors.

    3. Steve – Thanks for sharing your story. It’s a good example of the fact that one specific diet doesn’t work for all people. Individual genetic differences factor into all disease states and it’s simply short sighted to suggest that any one diet is going to do the same thing for everyone. Good for you for figuring out what works for you!

    4. Hi Steven often the reason for colitis being better on a Paleo diet flaring up on a plant based diet is gluten. Paleo is gluten free and most people on plant diet consume gluten containing grains. Remove gluten and you may find removing garlic & onion helps too

  6. Hydrogen sulfide also appears to be a vasodilator, and is one of the components of garlic that seems to be connected to its being healthy. For instance: Of course I’ve heard that carbon monoxide also is used minutely in the body as a vasodilator, but that doesn’t keep it from being a poison. But anyone care to comment on when and how hydrogen sulfide is positive / negative for health?

  7. I am sorry but I had Ulcerative of colitis since I was a teen and I have been a vegetarian since 1978 and I changed to vegan 2 years ago but still suffer the same if not more. I think the way we eat is important like if we eat fast, and under stress it will make things worse. I am confused about Sulfur in our food that could cause this disease? there are so many facts to it including food, emotion and our lifestyle. Not all size fit all with our body’s chemistry.

    1. I too used to be a vegetarian and thought I had done something good for my health. I have since come to the conclusion that from a health perspective a diet that contains any substantial amount of dairy and eggs is from a nutritional standpoint no more healthful than one that contains meat. So really I would say that your healthful eating only started 2 years ago. Also you say “vegan”, but that only says what you don’t eat, not what you do. I would be curious to know if by vegan you mean a diet not only devoid of animal products, but consisting almost exclusively of whole plant foods with minimal processed/refined plant foods.

      And by processed/refined I mean food that has had its nutritional profile substantially changed. A vegan food can have whole plants in it, but if a substantial portion of the calories in the food come from refined sugar or refined oils, then I question whether it can be considered a whole food. To me an excellent example is salad, because what could symbolize a whole plant food dish more than just a bunch of torn raw lettuce leaves. And that would be correct if the salad just contained lettuce and other cut up vegetables and fruits (and maybe nuts and seeds). But just two tablespoons of dressing can completely change the nutritional profile. A simple salad with 3 cups of romaine lettuce and two tablespoons of regular ranch dressing gets 23 calories from the lettuce and 123 calories from the dressing (with 120 of those calories coming from refined oil).

      So if you aren’t already, I would highly recommend focusing on eating only nutritionally whole plant foods and eliminate to the greatest extent possible all refined grains, sugars and oils and see if that makes any difference.

      I do agree with you that stress can make every ailment worse. We are one single integrated and dynamic system. And as with any system, when one part is out of balance/rhythm it can upset the balance of the entire system. Our minds can directly affect how our bodies function, largely through the sympathetic nervous system. Regulating our minds can help us regulate our bodies.

      I wish you good luck as you work to find ways, be that diet, exercise or meditation/mindfullness, to help your body function better.

    2. Hmmm…I think the cause of UC is multifactorial and yet unproven theories abound. Personally, I think my UC started after a course of Augmentin (having never had antibiotics at 22yrs old) prescribed for strep D throat infection..change of gut microbiome perhaps triggering a genetic predisposition to UC (aunt has UC)..the other theory about mycobacterium seems plausible too in my humble opinion. My diet changed at the time of diagnosis too having moved away from home to study..prior to that my diet was primarily veg/potatoes and meat…no fast food and no sugary processed crap…mind you there is a gazillion antibiotics and God knows what other chemicals used in the meat industry in ireland.Whole food plant based now which is quite the fiber challenge without a colon!

    1. Purely anecdotally: as an expat in Mexico, lot’s of folks were getting Montezuma’s revenge which took them to the G.P. who prescribes antibiotics which helped until C.diff showed up.

      The Veg folk among us tended not to get ‘distress’ in the first place which meant no C.diff

      However, anybody needing serious antibiotics in a hospital can be at risk.

      1. Thank you for the reply! My mother was hospitalized with C.diff in 2012, but it could have been diagnosed earlier if the doctors had only checked it off on the stool test form. They asked if my mom had taken any antibiotics within the past year, but she had not. The infection really destroyed her gut and to this day there are a number of things she can’t eat now that she used to eat before acquiring the infection. So I have always been wondering how she could have acquired the infection when she had not taken any antibiotics previously.

        Is it possible to have an imbalance of gut bacteria due to diet (we used to eat pretty unhealthy before she got sick) that could lead to a possible infection?

        1. Gosh, I heard of one C.diff that came from rose-thorn scratch. It is out there; more so in ‘sterile’ hospitals.
          Having nice healthy gut flora sure helps but we are all vulnerable to superbugs.
          Dr Gregor can sure point the way to a more resilient gut biome. Pass the broccoli.

        2. Hello Ingrid,
          Great question! The answer is YES, diet definitely influences the balance of gut bacteria. Dr. Greger has done a number of videos on this (see his list at the end of his article, above). Antibiotics are probably the single biggest risk factor for developing C. difficile — because antibiotics kill most of the healthy bacteria in our guts. But it sounds like your mother was a more unusual case in that she had NOT had any recent antibiotics.
          Vegans have a much healthier mix of gut bacteria (“colonic flora”) than do meat-eaters, so we are at lower risk of developing C. diff. I hope this helps.

          1. Thank you ToBeAlive and Dr. Jon for your replies. I will get into watching those videos real soon. Your replies answered my long suspicion of the possible cause of the infection. I am really glad I found this website too. Happy Holidays everyone :-)

  8. Hmm. I don’t know… I have Crohn’s disease (with Colitis) and have been vegan for 10+ years. All I know for certain is that eating certain sulfur-rich foods such as bell peppers, onions and garlic gives me incredible diarrhoea, wind and pain. I’m completely fine with cruciferous vegetables though.
    But am allergic to certain fruits and vegetables (Birch Pollen and Latex allergy) – which I never had before being diagnosed with the shitty Crohn’s nearly 10 years ago when I was a life-long vegetarian. I take no medication for the Crohn’s and am surgically intact (*touch wood) because of my “diet” but I have never felt so weak & tired, in agony and insatiable (food) in my life. I’m 52 yrs old and feel twice that. My body craves dairy as I previously had Pernicious Anaemia and Osteomalacia/adult Rickets (B12 & Vit D deficiencies) which I replaced the deficiencies with high dosage supplements – and still take to maintain my levels – which have dropped dramatically again.
    I’m just ranting here, looking for some kind of explanation as to why me and not the person who eats junk food, never exercises, …? So far, I can put it down to stress and an inherited disorder (Thalassaemia Beta) but nothing else other than 20+ years of high doses of iron supplements and the occasional pain-killer for a back problem that has ailed me since my 20’s. I’m the only one in the family affected with Crohn’s/colitis and also the only vegan.
    A good example as a healthy vegan I am not! But why?

  9. I have been following a Whole Food Plant Based Diet for over 2 years. I have had Ulcerative Colitis for 40 years. In March I had my 1st colonoscopy that showed no sign of the disease and I stopped taking the immunosuppressant medication 6 MP in April and continue to be free of Ulcerative Colitis.

    Unfortunately I just came down with a nasty case of the shingles. I read online that a Vegan diet may be high in L-Arginine and low in
    L-Lysine. And a diet high in L-Arginine and low in L-Lysine can feed the
    family of herpes viruses that activate herpes and the varicella-zoster virus.The recommendation is to focus on eating more foods that are high in L-Lysine or take a Lysine supplement. Dr. Greger do you know if there is any truth to that
    claim? Would love to hear whether you have come across any research on this subject. And if so what your recommendations would be. Thank-you.

  10. Been married 50 years to Bobby who now has Parkinson’a and I have MS and not walking for the last 32 yrs. when I taught school for 21 yrs. and retiring because of my MS. Teaching 14 yrs. in a 4th grade classroom then took over teaching P.E. for the next 9 yrs. at a new school and very active on the playground. Even taught dancing and played all sports. In fact, I won in 1963, the LA Badminton State Championship in Singles & Doubles. Then MS put me walking with a can, thus I took retirement 32 yrs. ago. Bobby has a mild case of Parkinson’s, a little hand shaking but then he just spent 7 days in the hospital dehydrated from his diarrhea at death’s door. Then spent 7 days in the hospital just getting IV’s to live again. Didn’t pass the CT Scan showing just ray intestines, they said like a 3rd degree burn, raw intestines. Bobby kept saying it hurt to eat, now I knew WHY? Started on bags of Remicade to heal the gut. I love Yogurt but he won’t touch it. Went to the library for a book on Crohn’s & Colitis. In 50 yrs. he would not touch oatmeal. Well, now, I am having him eat a bowl of oatmeal every morning with his eggs, bacon or sausage and a plate full of fruits(blueberries, strawberries, kiwi, blackberries, raspberries, biscuits and my smoothie. When before all he would eat for breakfast was a banana. Still won’t touch Yogurt or Kefir that I love every day but all normal foods and today is Christmas Day.
    Can eat pork, beef, chicken, lamb, and turkey. Not gluten free at all. I had tried 6 months of gluten-free, hated it and it did not work for my MS. He has come alive since coming home on Halloween night when he was unable to walk in the house w/o my walker. I was shocked but now in 4 weeks he totally back to normal and driving me and walking the whole WalMart Super Center. Hasn’t found a food that disagrees with him in 2 months since Halloween.

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