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The role of diet & nutrition in IBD

Can food cause IBD?

As IBD affects the digestive system, many people naturally wonder if there is a possible link between diet and IBD. A considerable amount of research has been undertaken to look for a connection, and scientists have investigated a wide range of food and nutrients to see if they play a role in the development of the disease.  Currently, there is no clear evidence that any particular food or food additive directly causes IBD.

However, some researchers think that there may be some sort of link between diet and IBD. One suggested link is with a diet high in fats and sugars and low in fruit and vegetables. Researchers have noted that in the past, IBD rates have been lower in non-Western countries such as Japan than in Western Europe and North America. However, over the past few decades, the number of people with IBD in Japan has been rapidly increasing. As many Japanese people now eat a more westernised diet (a diet typically high in fats and sugars), the suggestion is that it could be this change in diet which has led to the increase in IBD.

There have been other research studies which have come to similar conclusions about diets high in sweets, cakes and/or red meat. Researchers have also found a possible link between UC and some types of fat, such as trans-unsaturated fats like lineolic acid (found in oils such as corn and sunflower oil). Lack of dietary fibre may also play a role - another study found that women whose diets contained a lot of fruit were less likely to develop Crohn’s Disease, but not UC.

Nevertheless, the overall picture is still not clear - some research findings contradict each other, and scientists continue to debate exactly whether and how food may play a part in causing IBD.

What happens when we eat food?

To understand the effect that food has on the gastrointestinal (digestive) system, it can be helpful to know the main features of the system and what happens when we eat.

The gastrointestinal tract (gut) is like a long tube running all the way from the mouth to the anus. Its main purpose is to break down (digest) the food that we eat so that we can absorb the nutrients in the food. These nutrients are used to give us energy and help our bodies to grow and repair themselves.

When we eat, food passes down the oesophagus (gullet) and into the stomach, where gastric (digestive) juices break it down further into a porridge-like consistency. The partly digested food then moves through the small intestine (also known as the small bowel). Here it is broken down even further so the nutrients (useful parts of food) can be absorbed into the blood stream.

The waste products from this process - liquid and undigested parts of food - are then pushed into the colon (also known as the large intestine or large bowel). The colon absorbs the liquid, and the left over waste forms solid stools (faeces). These collect in the last part of the colon and rectum until they are passed out of the body in a bowel movement.

When the small intestine is inflamed, as it often is with Crohn's disease, the intestine becomes less able to fully digest and absorb the nutrients from food. Such nutrients, as well as unabsorbed bile salts, can escape into the large intestine to varying degrees, depending on how extensively the small intestine has been injured by inflammation. This is one reason why people with Crohn's disease become malnourished, in addition to just not having much appetite. Furthermore, incompletely digested foods that travel through the large bowel interfere with water conservation, even if the colon itself is not damaged. Thus, when Crohn's disease affects the small intestine, it may cause diarrhoea as well as malnutrition. Should the large intestine also be inflamed, the diarrhoea may become even more extreme.

In ulcerative colitis, only the colon is inflamed; the small intestine continues to work normally. But because the inflamed colon does not recycle water properly, diarrhoea can be severe.

Can food cure IBD

While you may come across a number of diets claiming to cure IBD, the majority of these do not have sufficient evidence to support their claims. But there is considerable evidence that specific aspects of nutrition are important in IBD, and that, as with any on-going health condition, it is vital to keep well nourished. So, it is important to eat as healthy and balanced a diet as possible.

Although diet may not cure IBD, some people may find that it helps to make small alterations to their diet. For example, some people have found that certain foods, for example spicy foods or dairy products, seem to trigger their symptoms or make them worse. On the other hand, some people may find they have no particular triggers - it varies from person to person. It may help to keep a food diary in order to keep track of what you eat and when your symptoms occur.

However, if you find that cutting out foods makes no difference, you should add them back into your diet, because you do not want to miss out on important nutrients. It is important to get advice from your doctor or from a qualified dietitian before you make any significant changes.

Healthy eating with IBD

Food provides us with nutrients that give us the energy to go about our daily lives, and to help our bodies grow and repair themselves. It is important that we eat a healthy balanced diet in order to receive all the nutrients our bodies require.

There are five main groups of nutrients:

  • Carbohydrates - a major source of energy. There are two main types of carbohydrates - simple and complex. Simple carbohydrates are sugars, and can be found in fruit, vegetables and milk, as well as in confectionery, cakes and biscuits. Complex carbohydrates include starch and fibre, and are found in foods such as pasta, potatoes and bread.
  • Protein - important for the growth and repair of body tissues, as well as being used to make enzymes, hormones and muscle. Protein can be found in meat, poultry, eggs, cheese, beans, nuts and pulses.
  • Fat - a concentrated energy source. It also helps protect our internal organs, and is required for our glandular and immune systems, and to help absorb certain vitamins. Fat can be found in foods such as meat and dairy products.
  • Vitamins - a group of nutrients found in very small amounts in food. They are important for cell function, growth and development. There are 13 essential vitamins, each vitamin has an important job in the body. An example is vitamin C, which is important for healthy teeth and gums. It also helps the body to absorb iron, and helps with wound healing.
  • Minerals - chemical elements found in food. They are needed in small amounts to help the body stay strong and function properly. Examples include calcium which is needed for strong bones, and iron which is needed for red blood cells.

What about Probiotics and Prebiotics

Probiotics are a mixture of live ‘friendly’ (beneficial) bacteria taken by mouth. The aim of taking probiotics is to increase the number of beneficial bacteria in the colon. Probiotics can be found in special fermented milk drinks and yogurts, or be taken in tablet or powder form.

Research suggests that some probiotics may have a use in maintaining remission in people with UC. As yet, there is no clear evidence that probiotics can help induce or maintain remission in people with Crohn’s Disease.

Prebiotics are dietary substances, mainly consisting of non-starch polysaccharides and oligosaccharides (types of carbohydrates), which are poorly digested in the small intestine of humans. They provide a food source for beneficial bacteria in the gut, and encourage them to breed. Prebiotics favour the growth of beneficial bacteria over harmful bacteria. Examples of foods containing naturally occurring prebiotics include wheat, onions, bananas, garlic, leeks and honey. However, the role of prebiotics in IBD is not fully understood and as yet there is no evidence that taking prebiotics will help people with IBD.

What about herbal remedies and other supplements?

There are plenty of supplements that claim to treat IBD. Some people with IBD have found that particular herbal remedies, such as Aloe Vera or Curcumin, do help relieve their symptoms. However, many of these supplements are still being researched, and although they may help some people, there is no conclusive evidence about when or how they will work. It is difficult to know, with confidence, whether there is a direct physical effect, or a general psychological benefit (placebo). Also, everyone is different, and what may help one person may not have any effect on another. If you do want to take a complementary or alternative product, consult your doctor first and do not stop any prescribed medication without discussion, even if your symptoms improve. Herbal remedies are not as carefully regulated as conventional prescribed medications, and may have serious side effects.

Common IBD symptoms and useful dietary alterations


Diarrhoea is one of the main symptoms of IBD. If you have a lot of diarrhoea and pain you may find it tempting to stop eating. However, it is important to continue eating and drinking enough in order to stay nourished and hydrated. Some people find that certain foods, such as those containing a lot of fibre, can make their diarrhoea worse. It may help to avoid these foods during a flare-up. Spicy and fatty foods, alcohol and caffeine can also increase diarrhoea. 

Bloating and Wind 

Many people with IBD are concerned about the effects of bloating and wind, such as tummy gurgles and flatulence (breaking wind). Bloating and wind may come from swallowing too much air when eating or talking. It can also be caused by over-production of gas by bacteria in the colon. If you want to reduce the amount of gas you are passing, you could try cutting down on foods that are known to be more gas producing. Common examples include spicy foods, legumes (peas, beans), and brassica vegetables (cabbages, cauliflower, broccoli). Fizzy drinks, caffeine and foods containing sorbitol (an artificial sweetener) have also been found to increase bloating and wind.


Some people with IBD have constipation, particularly if they have proctitis (inflammation of the rectum). Constipation can be defined as opening the bowels fewer than three times a week, needing to strain, or passing hard pellet-like stools (faeces). You may find a stool passing through an area of inflammation in the colon particularly painful. Drinking plenty of fluids may help form softer stools which are easy to pass. It may also help to increase the amount of fibre in your diet, although this is not suitable for all people. If you are worried about constipation, speak to your IBD team or doctor. Some people may find oral fibre supplements or a stool softening laxative help to form easily passed stools - but you should talk to your IBD team first. 

Under-nutrition and weight loss 

Fluctuating weight is commonly seen in people with IBD, reflecting flare-ups and periods of remission. Weight loss can be a good indicator that you are not getting enough nutrients, and you should tell your IBD team if you have lost weight unintentionally. During a flare-up it is important to try and maintain your weight. Ways to put on weight could include eating little and often through the day, eating plenty of protein and energy rich foods, and simple alterations such as drinking soups and juices rather than just tea and coffee. Diets to increase or gain weight should be discussed with your IBD team to ensure that you are maintaining a healthy balance.

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