Background
Over the years there have been a number of different approaches to diet in IBD, ranging from complete bowel rest and dietary exclusion to high energy, high protein diets, and from low fibre diets to high fibre diets. Even now advice may vary from one treatment centre to another. Understandably, many people are confused as to which diet they should be following.

To some extent advice will vary depending on whether you have Crohn's disease or ulcerative colitis, the site of the disease and past and current treatments. However, it is generally agreed that in most cases of IBD, the normal guidelines for a healthy balanced diet should be followed.

What is a balanced diet?
The basic dietary principles in IBD are no different to those for the general population. Starchy foods (potato, rice, bread, pasta, breakfast cereals) should form the basis of all meals. Fruit and vegetables should also form a large part of the diet, unless otherwise indicated, with at least five portions per day. Dairy foods, which provide calcium and protein, should be taken three times a day. Protein foods, (meat, fish, eggs, pulses, nuts, etc.) are essential for growth and repair and also provide iron - these should be taken twice daily. Other foods (spreads, oils, fatty and sugary foods, alcohol, etc.) provide few nutrients other than energy but add variety to the diet - these should be enjoyed in moderation only.

However, having an illness of the digestive tract will have an effect on the way in which your body handles food. For some people this may mean they have difficulty in eating such a wide variety of foods or that they have increased requirements for certain foods.

How does inflammation affect dietary requirements?
When your gut becomes inflamed you may experience pain, discomfort or nausea. These can cause your appetite to be poor which, after a while, will lead to weight loss.

You may also find you are losing weight because your digestive tract is not absorbing food as efficiently as a normal gut. In Crohn's disease, damage to the lining of the small intestine may reduce its capacity to absorb nutrients. This can cause the body to become short of energy or deficient in certain minerals and vitamins, which may make you feel tired. If you have a fever this will increase the body's need for energy. The increased energy requirement is to some extent offset by a reduction in the amount of physical activity taken so it is best to take it easy when suffering with active disease.

Food residue that is not absorbed in the small intestine will enter the large intestine (or colon). An inflamed large intestine may not be able to reabsorb sufficient water or salt from the residue which will result in the passing of a large volume of diarrhoea or semi-solid stool. You may also lose some protein from leakage of the damaged intestinal lining. If this lining bleeds there is a risk of becoming deficient in iron which can lead to anaemia.

When a relapse has been treated you should then begin to feel much better with a return of your appetite. A nutritious diet, high in calories and protein, is then needed to replace lost energy and nutrients.

If your appetite remains poor for a while, you may find small, frequent meals and snacks easier to manage than a few large ones. Extra energy can be obtained from simple carbohydrates or sugars such as sweet drinks, biscuits and sugary desserts, but try to have these in addition to other foods rather than instead of them, as they supply little if any extra vitamins or minerals. Special high energy and nutritious drinks can be obtained on prescription from your doctor. Medical advice should be sought if you are losing weight or struggling to regain it.

Fluids need to be replaced during bouts of diarrhoea and vomiting to prevent dehydration. Usually this can be achieved by drinking more liquid but in severe cases, a solution of salt and glucose in water may be prescribed to improve absorption. In hospital, fluid losses are sometimes replaced by giving fluids into a vein.

Should the inflamed gut be rested?
When the gut becomes inflamed, eating frequently provokes pain because the lining of the intestine is irritated by food passing through. However, it is unwise to stop eating and drinking altogether as this will make the body very weak.

In certain circumstances, for example if the gut has become completely obstructed, it may be necessary to stop eating and receive nutrition via a vein into the blood. This is known as Total Parenteral Nutrition (TPN). In Crohn’s disease TPN 'dampens' down inflammation in most cases and is sometimes used as a treatment or as preparation for surgery. This is not the case in ulcerative colitis although TPN is still used sometimes to provide nutrition when the gut is not working. Special artificial diets known as 'enteral diets' are also effective in Crohn's disease at reducing inflammation, but they are not helpful in ulcerative colitis.