Crohn's disease is an autoimmune disease, related to ulcerative colitis. Collectively they are known as IBDs - intestinal bowel disorders. The overall prevalence of Crohn's disease in the US population was around 1 in every 400 people in 2009(1). This is likely to be similar to the rate in the UK where 1 in 700 were recorded in 1995(2). However, it may well under represent the true prevalence however, due to undiagnosed cases.
Women are around twice as likely to develop this autoimmune condition than men, however before adulthood it is boys who are more likely to develop it than girls. Recent news stories in the UK have reported large rises in the prevalence of Crohn's disease(3). This is in contrast to ulcerative colitis whose prevalence has remained constant.
A direct cause of Crohn's disease is not known, however there are genetic and environmental factors that appear to affect risk of contracting Crohn's.
Genetically there is an association between the types of gene in at least 200 locations and Crohn's disease(4). Some of the more important genes may be:
- HP2, which is located on chromosome 16 and produces the protein zonulin which determines how leaky our guts are. Leaky guts increase the risk that bacteria in our intestines come into contact with cells of our immune system, triggering an immune response, which in susceptable people leads on to Crohn's disease.
- NOD2, which is also located on chromosome 16. People with deficient NOD2 genes produce too few anti-bacterial proteins called alpha-defensins(5). These normally populate the crypts lining our intestines. Too few and we can get bacterial overactivity in our intestines.
Environmentally probably the most important mechanism that could affect Crohn's risk is the permeability of your guts(6). There are additionally a number of other factors that are associated with increased risk of Crohn's.
- NSAID drugs such as aspirin, ibuprofen and naproxen are associated with increased risk(7). They can damage the intestinal lining, creating a more active immune response in the gut, increasing risk of Crohn's.
- Antibiotics have an association with increased incidence of Crohn's, perhaps not surprising if Crohn's is partly caused by an interaction between our immune system and bacteria in the gut. Specifically antibiotic usage can change the type of bacteria in the gut, often causing more pathogenic (disease causing) bacteria to predominate.
- The contraceptive pill has also been associated, especially when used over extended periods of time or by smokers(8).
- Smoking gives a 2-3 fold increase in risk of developing Crohn's(8).
An overreaction by the body's immune system to bacteria in the gut seems to characterise the start of Crohn's. Specifically parts of the immune system called T cells and macrophages produce chemicals called Interferon gamma (IFN-y) and Interleukin 12 (IL-12) respectively. These are produced in response to a perceived threat in the gut. These two chemicals are responsible for the high levels of inflammation that appears in the guts of people with Crohn's.
Inflammation appears in all parts of the gut, although most typically affecting the lower part of the small intestine (ileum), and the upper portion of the large intestine (colon). Inflammation manifests itself as swollen lymph nodes within the abdominal cavity, and ulceration (open sores) in the deeper fibrous and muscular layers surrounding our gut (alimentary canal). The open sores may enlarge and end up connecting one part of the intestines with another or indeed a nearby organ. The passageways so produced are called fistulae.
A fistula is defined as "an abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs".
These changes and others in the body lead to the common symptoms of Crohn's such as:
- Abdominal pain
- Fatigue - as a result of bleeding from ulcers and lack of iron.
Symptoms occur during flare ups that characterise IBDs such as Crohn's. Complications that occur with the passing of time include vitamin and mineral deficiencies. Often iron, folate and vitamin B12 deficiencies occur, which can markedly affect chronic disease risk as people with Crohn's age.
Drugs that are used to treat Crohn's include sulfasalazine and 5-ASAs, which are used to treat the inflammation in the bowel. Antibiotics are often used to treat complications of Crohn's, with steroids or other non-steroidal anti-inflammatories (NSAIDs), used to reduce the overall immune response.
The problem with much of the drug therapy relates to the significant long term side effects of immune suppressing drugs.
It is hard to come by specific nutritional guidelines for Crohn's. That is because there is not a great deal of evidence in this area. Many mainstream medical authorities suggest the standard diet recommended by health authorities, such as the "EatWell plate" promoted by the UK Government. They then add that you should avoid foods that cause flare ups for you.
Unfortunately this sort of diet is unlikely to be the best foundation for reducing Crohn's symptoms. In general a primal diet emphasizing plenty of meat, fish, eggs, vegetables and fruit, but not to many grains is probably the best approach.
However, there are some additional nutritional considerations also, which are worth noting:
Butter, cheese and yoghurt, contain some nutrients that can be in short supply for someone with Crohn's. These include the fat soluble vitamins: A, D, E and K2, as well as calcium and probiotic bacteria.
Fruit and veg
Consuming fruit and vegetables containing fermentable sugars can make symptoms worse. Also fruit and vegetables containing insoluble fibre can be problematic. If you have Crohn's and suffer with bloating and stomach pain it's worth experimenting to see if reducing the amount of dietary insoluble fibre helps you. To do this cut down on: aubergines, peppers, celery, brassica (cauli, broccoli and cabbage) as well as lettuce and watercress.
Eating the following vegetables should be OK: root vegetables (carrots, parsnips, beetrooot and squash) as well as all types of potato.
Another useful strategy is to reduce the variety of vegetables you eat in one meal, remove stems from broccoli and cauliflower and steam or boil the vegetables sufficiently to soften them.
Vitamin D, primarily available from sun exposure as well as fatty foods, such as oily fish, liver and eggs is associated with a reduced incidence of Crohn's disease. Trials using vitamin D to treat people with Crohn's have shown some promise, more than halving the relapse rate in one small trial(9).
Polyunsaturated fats ratio
Polyunsaturated fats are essential for survival. They are found in seed, nuts, fish and their oils. There are two types. Omega 3 (w3) fats are found in fish and omega 6 (w6) fats are found in nuts and seeds. The two types of fat have opposing effects in the body. The w3 oils (fish) are anti-inflammatory and w6 fats (nuts and seeds) are inflammatory. We need a balance between both for good health, and there is some evidence that most people are consuming too much w6 and too little w3 fats. The effect of this for someone with Crohn's could be to have increased levels of inflammation in the gut.
Food particle size
Many people with Crohn's will experience strictures (narrow areas) in their intestines. These can prevent food particles over a certain size passing through. In this case it is best to avoid certain types of foods for a period of time until resulting inflammation and soreness has settled down. Foods to avoid include nuts, large seeds and foods containing insoluble fibre, such as wheat bran and corn. Many raw foods can also be problematic also. For some people a liquid diet can help during flare ups.
Other nutrients such as folate can be required either as supplements or by eating foods with concentrated amounts of them. The need for such supplements will depend on the extent of damage to the small intestines and the types of drugs being used to treat the condition.
If you are experiencing diarrhoea don't forget to drink more. In hot weather especially, if you are sweating a lot, also eat some salty foods to replace any salt lost in the sweat.
Example diet for Crohn's
If you find that certain foods cause problems then don't eat them. Be careful with hard to digest foods such as raw vegetables, nuts and some fruits. Other than that, a diet that is based around meat, fish, dairy, vegetables, legumes and fruits should form the core of the diet.
- Plenty of sunshine
- Oily fish - 2-4 times per week.
- Liver - Once per week.
- Eggs - 4 times per week.
- Butter contains useful fat soluble vitamins.
- Liquid meals may be worthwhile when there are severe flare ups.
- Certain oils (corn, vegetable, soy, safflower and sunflower). Check on the ingredients lists of any packaged food items.
- Margarines. These are normally high in trans fats and of course the proportion of the w6 oil, linoleic acid is higher than in butter. Typically 23% of margarine is linoleic acid, compared to just 3% in butter(11).
- Shop bought sauces such a mayonnaise and other salad dressings.
- Nuts, large seeds, corn, wheatbran and raw vegetables during flare ups, especially if narrowing of the intestines is known to be present.
There are a few diets reported to be effective by some sufferers from Crohn's. These include the GAPS diet, which was originally developed to help people with autism(12). This diet excludes grains, polysaccharides (all starches) and disaccharides (most sugars). As such it is quite a strict diet, but could be considered for those really struggling with poor health due to their Crohn's.
The initial stage of the GAPS diet begins with meat being consumed alongside bone broth. Vegetables are used to make the bone broth, but are not consumed. Just get some quality meat from your local butchers, and using the smaller bones and some vegetables boil up for 8-48 hours. Further instructions can be found on the internet(13).
As recovery proceeds a more normal diet can be adopted. This diet may not work for everyone, but it has been successfully used by a number of people with Crohn's. There are some case studies on the net (14).