Food, digestion and the gut

Your gut is a long tube that starts at your mouth and ends at your bottom. It breaks down food so your body can get energy and nutrients from it. This is called digestion. Muscles in the walls of your gut squeeze the food along in a wave-like movement.

The gut

When you eat, food travels down your food pipe into your stomach. Your stomach makes acid, which kills germs. It also churns the food into a porridge-like consistency. The food then passes into your small bowel.

Your small bowel breaks down the food and absorbs energy and nutrients from it. Anything that is not absorbed is squeezed along to your large bowel.

Your large bowel absorbs liquid from the food. This usually leaves solid waste – poo.

Your body stores poo in a part of your large bowel called your rectum until you go to the toilet.

It usually takes around 1 to 4 days for food to pass all the way through your gut. But this can vary a lot from day-to-day, from person-to-person and depending on what you have eaten.

How do Crohn’s and Colitis affect food and digestion?

Crohn’s and Colitis cause inflammation in your gut.

• Crohn’s can cause inflammation or patchy ulcers anywhere from your mouth to your bottom.
• Colitis causes inflammation in your large bowel.

If your small bowel is inflamed, you might not absorb nutrients or liquids as well as usual. So if you have Crohn’s, you might find it hard to get all the energy your body needs. You might also have low levels of some vitamins and minerals. If your large bowel is inflamed, you are likely to absorb most nutrients but you might not absorb enough liquid from your food or drink.

When you’re feeling unwell, it can also be difficult to eat enough of the right nutrients to stay well and keep a healthy weight. You might not feel like eating much, or you might only be able to tolerate certain foods. You may have a low appetite or lose weight without trying to. Some people might gain weight. This could be because of changes to your diet, or as a result of some treatments for Crohn’s or Colitis, such as steroids.

Many people with Crohn’s or Colitis change what they eat to try to help manage their condition. This can make it hard to get the right balance of nutrients. It can also change your relationship with food.

Many people say they do not get as much pleasure from eating as they used to. Changing your diet can also affect your family life, especially if you do not eat the same food as other people you live with. Up to 1 in 4 people with Crohn’s or Colitis say they avoid eating out or social events that involve food. This can be especially hard if food is a big part of your culture. You might feel excluded, or guilty for turning down food that has been offered to you. Some people find that taking a prepared meal from home can be helpful if they’re going to a community event where there might be food they can’t eat.

Many individuals find it helpful to learn more about diet and nutrition. They have told us that making informed food choices has had a positive effect on their overall health

Can food cause Crohn’s or Colitis?

We don’t know exactly what causes Crohn’s and Colitis. It is probably a combination of:

The food you eat can affect your health in lots of ways. It is a complicated relationship. Food can have direct effects on the lining of your gut. It can affect your immune system. It can also change the balance between helpful bacteria and harmful bacteria that live in your gut. So what you eat might affect your risk of getting Crohn’s or Colitis, but there is not enough evidence yet to say for certain.

• Ultra-processed foods might increase the risk of developing Crohn’s. Ultra-processed foods contain additives like colourings, preservatives and sweeteners. They include shop-bought cakes, biscuits, pastries and sweets, ready meals, sausages and factory-made bread and breakfast cereal. They are often high in sugar, salts and unhealthy fats, and low in fibre, vitamins and minerals.
• A diet that is high in a type of fat called omega-3 fatty acids, high in fruit and vegetables and low in omega-6 fatty acids might lower your risk of developing Crohn’s or Colitis. Omega-3 fatty acids are found in foods like oily fish, leafy green vegetables, nuts and seeds.

Can food cause flare-ups?

Most people living with Crohn’s or Colitis feel that certain foods can trigger flare-ups. But so far, there is very little scientific evidence to prove this. Researchers are looking into it to try to find out more about how diet affects flare-ups.

Can food trigger symptoms?

Some people find that what they eat has little effect on their symptoms. Others find that certain foods trigger symptoms and cutting down on those foods helps. In some cultures, making and eating spicy food is common. Some people with Crohn’s or Colitis may find that eating spicy food makes their symptoms worse.

You could use a food diary or app to find out if any foods seem to affect your symptoms. If you find any possible triggers, it’s a good idea to discuss them with your IBD team or dietitian before making any big changes to your diet.

Changes in symptoms after eating certain foods may not mean that your Crohn’s or Colitis is active or flaring up. Food can sometimes trigger symptoms in people without Crohn’s or Colitis too.

When your Crohn’s or Colitis is active, it can be hard to work out if a particular food is a trigger or if you’re getting symptoms because you’re in a flare-up. It may be easier to identify possible trigger foods when your symptoms are under control.

Can food cure Crohn’s or Colitis?

You might hear about people who manage their Crohn’s or Colitis through diet alone, or diets that claim to cure Crohn’s or Colitis. But there is no evidence that these work. And they often restrict particular foods or food groups, so if you follow them for a long time, you may miss out on important nutrients.

However, there are effective nutritional treatments that are sometimes prescribed to treat Crohn’s.

What the guidelines say

Researchers agree that diet is important in Crohn’s and Colitis. But at the moment, there is not much high-quality evidence to say exactly what foods could be helpful and what foods could be harmful. It is also something that may vary a lot from person-to-person. Some people find that certain foods make their symptoms worse. The same foods might not cause any problems for another person. So there is not any particular diet that works for everyone.

There might be times when your IBD team recommend making other changes to you diet. This could happen if:

• You have a narrowing (stricture)
• You are not getting all the nutrients you need
• You have particular symptoms that might improve if you change your diet
• You need nutritional treatments

Healthy eating

If you have Crohn’s or Colitis, it can be difficult to eat a healthy, balanced diet. This means you have a higher risk of malnutrition than other people. Malnutrition is when you do not get the right amount of energy or nutrients. It can mean that you are not getting enough, you are getting too much, or you are getting the wrong balance of energy or nutrients. Malnutrition can make it harder for your body to heal and fight off infections.

You might find it hard to eat well when you’re in a flare-up. But when your condition is under control, eating a healthy, varied diet helps you get the right balance of energy and nutrients. This is good for all aspects of your health, not just your Crohn’s or Colitis.

The Eatwell Guide is a useful starting point. It shows how much of each of the different food types you should aim to have in your diet. It is based on everything you eat and drink over a whole day – not necessarily in each meal.

Fruit and vegetables

Fruit and vegetables should make up more than a third of the food you eat. They can be fresh, frozen, dried or canned. They’re a good source of vitamins, minerals and fibre.

 Ask your GP, IBD team or dietitian for advice if you have problems eating fruit and vegetables, for example, if you have a stricture. Vegetables that are peeled and well-cooked can be easier to digest.

Starchy foods

These should make up over a third of the food you eat. They give you energy and nutrients. Starchy foods include:

• Bread
• Chapati
• Paratha
• Banku
• Potatoes
• Yam
• Plantain
• Rice
• Gari
• Fufu
• Pasta
• Breakfast cereals

Choose wholegrain or wholewheat options and leave the skin on potatoes if you can – they contain more fibre.

Beans, pulses, fish, eggs, meat and other proteins

Your body needs protein to grow and repair itself. Protein-rich foods also contain vitamins and minerals.

Try to eat less red meat, fatty meat or processed meat, like sausages, bacon or cured meats. Beans, peas, chickpeas and lentils are healthy alternatives. Tofu, bean curd and mycoprotein (Quorn) are also good sources of protein.

Dairy and dairy alternatives

Have some dairy or dairy alternatives.

Dairy foods are good sources of proteins, vitamins and minerals – especially calcium. They include milk, cheese, paneer, yoghurt and fromage frais. Go for lower-sugar products if you can.

Dairy alternatives include soy, oat or nut milks. If you use dairy alternatives, try to make sure they are unsweetened and have added calcium. These are sometimes called fortified drinks.

Oils and spreads

Oils and spreads are fats. They are high in energy so you only need small amounts. Most people have too much fat in their diets.

There are different types of fat, and some are healthier than others. Unsaturated fats like olive oil, fish oils or nut oils are healthier than saturated fats like butter, ghee or lard. Choose lower-fat versions if you can. Vegetable fats are healthier than animal fats.

Foods to eat less often and in small amounts

Foods or drink high in fat, salt or sugar include:

• Biscuits
• Cakes
• Crisps
• Carrot punch
• Cornmeal pudding
• Chin-chin
• Gulab jamun
• Puri
• Rasmalai
• Ice-cream
• Full-sugar drinks

Butter, ghee, palm oil and coconut oil are also high in fat, sugar or salt.¹⁵

You do not usually need these foods or drinks in your diet, but it’s OK to have them occasionally and in small amounts. If you eat them a lot, cut down if you can, especially if you are above a healthy weight.

Drinks

This could be water, tea, coffee, lower-fat milk or sugar-free drinks. Fruit juice and smoothies also count but they are high in sugars. When you are well, you should try to limit juice or smoothies to one small glass per day.

Alcohol

There is not enough high-quality evidence to know for certain if drinking alcohol could increase your risk of a flare-up. But many people with Crohn’s or Colitis say that alcohol makes their symptoms worse.

If you drink alcohol, try to keep to the recommended limits.

Where to get advice on your diet

It can be difficult to find reliable information about food for people with Crohn’s or Colitis, and some of the information you get can be conflicting. Many people use ‘trial and error’ to try to work out what foods to eat and what to avoid, but this may not work well and it can lead to missing out on important nutrients. Be careful with information about diet you find on the internet. It may not be reliable and it could be dangerous.

If you’re not sure where to find trustworthy information, you could ask your GP or IBD team for recommendations. Some may be more knowledgeable about the role of diet than others.

You could also contact Crohn’s & Colitis UK or the other organisations listed at the end of this page.

Your GP or IBD team might be able to refer you to an NHS dietitian. Some people choose to contact a private dietitian. If you cannot get an appointment with a dietitian, your IBD team may be able to give you information about diet.

Enteral and parenteral nutrition

If you’re in a Crohn’s flare-up, you’re struggling to get enough nutrients from your diet or your bowel is not working, you might need nutritional treatments.

Nutritional treatments give you the energy and nutrients your body needs. There are two main ways to have them:

• Enteral nutrition: liquid nutrition you drink or have through a feeding tube
• Parenteral nutrition: liquid nutrition that you have through a drip into a vein

Enteral nutrition

Enteral nutrition is a liquid diet. It comes as a ready-made drink or a powder that you mix with water. You can drink it, or you can have it through a feeding tube that goes straight into your gut. It is nutritionally balanced and gives you the energy and nutrients your body needs.

Depending on why you need it, you might have enteral nutrition instead of eating food. This is called exclusive enteral nutrition. Or you might have it alongside other food and drink. This is called partial enteral nutrition.

Exclusive enteral nutrition

Exclusive enteral nutrition is a liquid-only diet. It is sometimes used to treat Crohn’s, particularly in children. It is not helpful for people with Ulcerative Colitis. It might sometimes be used if you have a severe flare-up, or if you’re having surgery for Crohn’s.

Exclusive enteral nutrition is often the first-choice treatment for children with Crohn’s. It works as well as steroids at getting Crohn’s under control. It also improves growth and nutrition in children with Crohn’s.

In adults, exclusive enteral nutrition does not seem to be as good as steroids at getting Crohn’s under control. But this might be because it is harder to follow a course of exclusive enteral nutrition so some people stop taking it. It can be helpful for people who cannot take steroids, or who do not want to take steroids. You might have it alongside immunosuppressant or biologic medicines. Some people might have it before surgery.

Partial enteral nutrition

If you’re struggling to get enough energy or nutrients in your diet, you might have enteral nutrition alongside normal food and drink. This is called partial enteral nutrition. For people with Crohn’s, having partial enteral nutrition as well as your usual medicines might help keep your condition under control.

For children with Crohn’s, partial enteral nutrition is sometimes used on its own or alongside medicines to help keep the condition under control for as long as possible. Or it might be used temporarily to help keep Crohn’s under control while other medicines take effect.

Parenteral nutrition

Parenteral nutrition delivers energy and nutrients straight into your bloodstream through a tube in a vein in your chest, arm or neck. This means it bypasses your gut completely. You might have it if you cannot absorb enough nutrients through your gut. Most people with Crohn’s or Colitis do not need it.

You might have parenteral nutrition if:

• You’ve had a lot of your small bowel removed and you do not have enough left to absorb the energy and nutrients you need (short bowel syndrome)
• You have a blockage in your bowel
• Your bowel is not working for a short time after surgery
• You have a fistula (a narrow tunnel or passage) that bypasses part of your bowel

You usually have parenteral nutrition in hospital. If you need it, your IBD team or dietitian will explain how it will work and how long you’ll need it for. Very occasionally, if you need it in the longer term, your IBD team might arrange for you to have it at home.

Eating during a flare-up

When you’re in a flare-up, you might not feel like eating much. But it is still important to get enough energy and nutrients. You might find it helps to:

• Drink plenty. If you’re losing a lot of fluid through diarrhoea or bleeding, you might want to use oral rehydration solution.
• Try to include healthy fats in your diet, like avocados, olive oil or smooth nut butters. These are high in energy so they’re a good way to keep your calories up when your appetite is low.
• Include foods that are high in protein. Your body uses more protein than usual if you are in a flare-up. So you might want to try protein-rich foods like eggs, dairy, meat, fish, pulses, beans, or nut butters.
• Eat fibre that is easy to digest, like well-cooked, peeled vegetables, bananas, melons, or fruit juice.
• If you’re struggling to eat full meals, soups or smoothies might be easier to manage.
• If dairy makes your symptoms worse, try dairy alternatives with added calcium, like oat, nut, rice or soy products.

When you start to feel better, it’s important to get back to eating a healthy, balanced diet. If certain foods made your symptoms worse during your flare-up, try adding them back in to your diet gradually when you’re well.

If your symptoms are always active and you find it hard to eat a healthy diet, ask if you can be referred to a dietitian for support.

Eating with a stricture

If you have a stricture (a narrowing in your gut), you may need to change what you eat to help prevent a blockage.

You might be advised to avoid foods that could block your gut, such as:

• Skins, seeds or stalks of fruit and vegetables
• Wholegrain foods
• Nuts and seeds
• Tough or gristly meat

Try to eat sources of fibre that are easy to digest, like well-cooked, peeled vegetables, bananas, melons, or fruit juice. Drinking plenty of fluid at mealtimes is also helpful.

If you’re not able to get enough energy or nutrients in your diet, you may need to have nutritional treatments.

Diarrhoea

Diarrhoea is a common symptom of Crohn’s and Colitis. Some people find that food has no effect on their diarrhoea. Others find that avoiding certain foods helps. You could use a food diary or app to find out if any foods seem to affect your symptoms.

Foods or drinks that might make diarrhoea worse in people with or without Crohn’s or Colitis include:

• Caffeine
• Alcohol
• Artificial sweeteners
• Liquorice

It is important to make sure you drink plenty of fluids to avoid dehydration.

Constipation

Some people with Crohn’s or Colitis get constipated. This might be caused by the condition itself, medicines you’re taking, or difficulty eating and drinking.

If you’re constipated, changing your diet can help. But it may take a few days or even a few weeks to work. You could try:

• Eating regular, healthy meals
• Gradually increasing the amount of fibre you eat
• Eating plenty of wholegrain foods, fruit and vegetables
• Choosing fruits or fruit juices like apples, pears, plums, apricots, raisins, peaches or prunes – these are high in a natural laxative called sorbitol
• Drinking plenty of fluid
• Taking regular physical activity

Bloating and wind

If you have Crohn’s or Colitis, you might feel bloated and gassy. Your tummy might make loud noises, or you might fart more than usual. It might be painful. Keeping a food diary can help you find out if any foods make your symptoms worse. Wind is not necessarily a bad thing, but if it is causing you problems, you might find it helpful to:

• Eat smaller, more frequent meals
• Drink plenty of fluid
• Cut down on foods that you’ve found make your gas worse
• Limit fizzy drinks, caffeine or alcohol
• Limit processed, sugary, spicy or fatty foods

If you have irritable bowel symptoms as well as Crohn’s or Colitis, you may find that a low FODMAP diet helps reduce bloating and wind.

Dehydration

You might get dehydrated if you’re not able to drink enough, or if your body is losing lots of fluid. This can happen if you have frequent diarrhoea, you’re being sick or you have a high-output stoma.

If you think you’re dehydrated, you could try:

• Drinking water or dilute squash. This might be enough to rehydrate you if you are only mildly dehydrated. If you are more dehydrated, you’ll also need to replace the sugars and salts your body has lost.
• Drinking sports drinks. These contain salts and sugars, although the balance can vary between brands.

Contact your IBD team if you think you are dehydrated and you have:

• A stoma that produces lots of watery output (a high-output stoma). Your team may advise you to limit some of your normal fluids and drink oral rehydration solution instead. This is designed to have the right balance of sugar and salt to reduce your fluid losses and help rehydrate you. Your team can tell you how much to take. Oral rehydration solution may not be suitable if you have diabetes or kidney problems.
• Short bowel syndrome (where you’ve had a lot of your small bowel removed and you do not have enough left to absorb the energy and nutrients you need). Your IBD team should tell you what to do.

Feeling or being sick

Some people with Crohn’s or Colitis feel sick and may be sick. Some medicines for Crohn’s and Colitis can also cause sickness. Here are some things that may help:

• Eating smaller meals – but have them more frequently, to keep up your overall food intake
• Eating lower-fibre foods – try white rice or white bread and limit wholegrain foods for a while
• Mashing or pureeing foods if you find them easier to keep down
• Eating foods containing ginger, like ginger biscuits, or drinking ginger tea
• Avoiding strong-smelling foods
• Avoiding fried, fatty or spicy food if they make your symptoms worse

Fatigue

Many people with Crohn’s or Colitis experience fatigue – extreme tiredness that does not go away when you rest.

Not having enough energy or nutrients in your diet is one of the things that can cause fatigue. If you have low levels of particular nutrients, taking the right supplements may help your fatigue. It’s also important to try to eat a diet that contains all the nutrients you need. But this can be difficult when your energy levels are low.

When your fatigue is bad, you may not have enough energy to cook or even to eat much. It can help to choose foods you enjoy. You could also ask friends or family to help with shopping and cooking. During times when you have more energy, you could batch-cook meals for a few days so you have food ready for days when your energy levels are low.

Crohn’s, Colitis and other conditions

Some people with Crohn’s and Colitis have other medical conditions that may involve changes in diet. Here, we cover some of the more common ones. This is an overview of how diet may help – we do not cover medical treatments for these conditions.

Sometimes, you might get conflicting dietary advice for different conditions. If you have complicated dietary needs, you might be referred to a dietitian.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is an illness that causes gut symptoms but does not show any signs of damage to the gut on tests. It can cause symptoms like cramping tummy pain, bloating and wind, diarrhoea or constipation. Around 10 in 100 people in the general population have IBS.

IBS, or IBS-like symptoms, affect more than 30 in 100 people with Crohn’s or Colitis. This means you might have gut symptoms even if your Crohn’s or Colitis is under control (in remission).

If you have IBS (or IBS-like symptoms) and Crohn’s or Colitis, following a low FODMAP diet might help you identify possible trigger foods. But it is not designed to be followed long-term. If you follow a low FODMAP diet, you should be supervised by a trained dietitian.

Coeliac disease and gluten sensitivity

Gluten is a protein found in wheat, barley, rye, or foods that contain them. This includes bread, breakfast cereals, pasta, cakes and many other shop-bought foods. There is no evidence to suggest that gluten is bad for Crohn’s or Colitis. But some people with Crohn’s or Colitis might also have coeliac disease or gluten sensitivity.

Coeliac disease is a condition where your immune system attacks the lining of your gut if you eat gluten. It causes symptoms similar to Crohn’s and Colitis, like diarrhoea, tummy pain, bloating and wind.

Some people do not have coeliac disease but get symptoms when they eat foods containing gluten. This is called gluten sensitivity. Scientists are not sure what causes gluten sensitivity. They think it might not be gluten that causes the problem, but other components of wheat, barley or rye.

In the UK, fewer than 1 in 100 people have coeliac disease. But around 13 in 100 think they are sensitive to gluten. This is higher in people who have Crohn’s or Colitis – around 25 in 100 people with Crohn’s or Colitis say they are sensitive to gluten. This can happen temporarily during a flare-up.

If you think you have coeliac disease or gluten sensitivity, speak to your IBD team or dietitian before changing your diet. It’s important to get a diagnosis so you can get the right monitoring and treatment. The tests for coeliac disease only work properly if you are eating gluten.

The treatment for coeliac disease is a gluten-free diet.

If you cut gluten out of your diet during a flare-up, try adding it back in to your diet gradually when you’re well.

Lactose intolerance

Lactose is a sugar found in dairy products, like milk, cream and cheese. An enzyme called lactase in the lining of your small bowel usually breaks it down so your body can absorb it. Babies usually have high levels of lactase, but older children and adults may not make enough lactase.

If lactose is not broken down, your body cannot absorb it. This is called lactose malabsorption. It might not cause any problems at all. But it can cause symptoms like diarrhoea, bloating, wind, tummy pain and feeling sick. If it causes symptoms, it’s called lactose intolerance.

In the UK, around 8 in every 100 people are lactose intolerant. People with Ulcerative Colitis have a similar risk of being lactose intolerant as the general population. But people with Crohn’s may have a slightly higher risk. Some people with Crohn’s or Colitis only get symptoms of lactose intolerance during a flare-up.

If you have Crohn’s or Colitis and lactose intolerance, cutting down on foods and drinks that contain lactose might help reduce the symptoms. You could choose dairy alternatives with added calcium or look for lactose-free dairy products. Check the ingredients on foods you buy to see if they contain lactose.

You might not need to cut out lactose completely – many people with lactose intolerance can manage small amounts of milk, especially if they have it with food. Once your symptoms have settled, try introducing lactose again to see if you can tolerate it.

Milk and dairy foods are important sources of calcium and vitamin D. If you follow a low-lactose or lactose-free diet, try to choose dairy alternatives with added calcium. Lactose-free cow’s milk products are still rich in calcium. You could also include other sources of calcium. If you cannot tolerate any calcium-rich foods, consider taking a calcium supplement.

Diverticular disease

Diverticula are small bulges or pouches in the bowel wall. They are very common, especially in people over 60. Most people do not know they have them. They are usually found during tests for something else.

Your IBD team might see diverticula during a colonoscopy.

Most of the time, diverticula do not cause any symptoms. If you have diverticula but they do not cause any symptoms, it is called diverticulosis. If they do cause symptoms, it’s called diverticular disease. Sometimes, diverticula can get inflamed. This is called diverticulitis.

Symptoms of diverticular disease can be similar to Crohn’s and Colitis – tummy pain, bloating, diarrhoea or bloody poo. Diverticular disease can also cause inflammation in the bowel. So it is sometimes difficult to tell if you have diverticular disease or Crohn’s or Colitis. Around 1 in 10 people with Colitis might have diverticular disease as well.

If you have diverticular disease and Crohn’s or Colitis, a healthy, balanced diet that includes wholegrains, fruits and vegetables helps you get the energy and nutrients you need. Drinking plenty of water and regular physical activity can also help keep your bowel function regular.

Eating disorders

Some people with Crohn’s or Colitis may develop a difficult relationship with food. The effect of food on your symptoms can affect how you feel about eating. You may also have weight changes that you may find challenging. Some people lose weight, especially during a flare-up. Others might gain weight. This could be due to changes in your diet, medicines you’re taking, or the illness itself.

Eating disorders, like anorexia, bulimia or binge-eating disorders, are slightly more common in people with Crohn’s or Colitis than in other people. So some people might have an eating disorder as well as Crohn’s or Colitis. Avoiding particular foods or following diets that limit whole food groups can increase the risk of developing an eating disorder. They can sometimes cause similar symptoms to Crohn’s and Colitis, like tummy pain, weight loss and vomiting. Because of this, it can be difficult to get the right diagnosis.

It’s important to speak to your GP or IBD team if your weight is changing or you think you might have an eating disorder. They can offer support and refer you to specialist eating disorder services if needed.

Heart disease

People with Crohn’s or Colitis have a slightly higher risk than other people of developing heart disease. This may be partly due to long-term inflammation. If you have heart disease as well as Crohn’s or Colitis, a healthy, varied diet can help you stay as well as possible.

The British Heart Foundation has more information on heart disease at bhf.org.uk

Diabetes

People with Crohn’s or Colitis do not seem to be any more likely than other people to get diabetes. If you have diabetes and Crohn’s or Colitis, a healthy, varied diet helps you get the energy and nutrients you need. If you find it difficult to balance your diet for diabetes with your Crohn’s or Colitis, ask your team to refer you to a dietitian.

Nutritional deficiencies in people with Crohn’s or Colitis

People with Crohn’s or Colitis may not have enough vitamins or minerals in their body, or may not get the right amount of energy. This is called a nutritional deficiency. It might happen if:

• You find it hard to eat the right balance of foods, especially during a flare-up
• Your gut does not absorb enough nutrients
• You lose important nutrients through diarrhoea
• Inflammation in your body affects the balance of fat, muscle and bone you have

Your IBD team should check if you have any nutritional deficiencies. This may include checking your height and weight, measuring your waist, hips or arms, checking how strong your grip is, and taking blood tests. They might also ask you about your diet.

Undernutrition

Many people with Crohn’s or Colitis have undernutrition. This means your diet does not give you all the calories you need and you might lose weight without trying to.

If you are undernourished, your IBD team should refer you to a dietitian. They can give you specialist advice and support. It is important to treat undernutrition because it can make it harder to keep your Crohn’s or Colitis under control.

If you are not getting enough calories in your diet, you could try:

• Eating foods that are high in energy and protein
• Snacking between meals – try to choose healthy high-calorie snacks like cheese, yoghurts, nut butters, or dried fruits if you’re able to tolerate them
• Having high-calorie drinks, like milkshakes or liquid supplements that you can buy from the supermarket

If this is not enough, your IBD team or dietitian might recommend enteral nutrition.

Overweight and obesity

Just like everyone else, people with Crohn’s or Colitis can be any shape or size. Some people lose weight, but others might gain weight. Weight gain in Crohn’s or Colitis might be due to changes in your diet, medicines you’re taking, or the illness itself. Some people with Crohn’s or Colitis might be overweight or obese. But they still might not be getting enough of the right nutrients.

Eating a healthy, varied diet, together with regular exercise, can help you manage your weight and get the right balance of nutrients. But it’s better to wait until your Crohn’s or Colitis is under control before trying to lose weight.

Vitamin and mineral deficiencies

Your body needs vitamins and minerals to work and stay healthy. Having Crohn’s or Colitis might stop you absorbing enough vitamins and minerals from your food. Or you might find it hard to get enough vitamins and minerals in your diet.

You are likely to have blood tests to check your vitamin and mineral levels. How often you need them depends on how well controlled your Crohn’s or Colitis is, whether you’ve had surgery, and whether you’re taking supplements.

Eating a healthy, varied diet helps improve the balance of vitamins and minerals in your body. But if blood tests show you have low levels of particular vitamins or minerals, your GP, IBD team or dietitian might suggest you take supplements. You could choose to take a multivitamin, but this might not give you enough of the particular vitamins or minerals you’re low on.

Iron

Around 1 in 3 people with Crohn’s or Colitis have low iron levels. This could be because you’re not getting enough iron in your diet, you’re losing blood, or you have problems absorbing iron from food. Low iron levels can lead to anaemia, where you do not have as many red blood cells as you should to carry oxygen around your body. This can make you feel tired, breathless or dizzy.

Anaemia caused by low iron levels is called iron-deficiency anaemia. If you have it, you’re likely to need iron supplements. You usually have these as tablets, capsules or liquid medicine that you take by mouth. But if you’re in a flare-up, your red blood cells are very low or you get bad side effects from oral iron supplements, you might have iron through a drip into a vein. This is called an iron infusion.

Your IBD team or dietitian might also check if you’re getting enough iron in your diet. If you’re not, you could try eating more iron-rich foods, like:

• Dark green, leafy vegetables
• Peas, beans and lentils
• Nuts and seeds
• Cereals and bread with added iron (fortified)
• Red meat (but try to keep to a healthy limit of 70g a day), fish or poultry

It’s harder to absorb iron from plant-based foods than from meat, but having some vitamin C at the same meal can help. For example, you could have a glass of orange juice with your fortified breakfast cereal.

Drinking tea or coffee with your meal – even decaf products – can make it harder for your body to absorb iron from your food. Try to wait an hour after eating before you drink tea or coffee.

Calcium and vitamin D

Calcium and vitamin D help keep your bones and teeth healthy. But many people with Crohn’s or Colitis have low levels.

• You might find it hard to get enough calcium in your diet. Taking steroids also makes it harder for your body to absorb calcium, so people on long-term steroids are especially likely to have low calcium.
• Your body makes vitamin D when your skin is exposed to sunlight. In winter, most people do not get enough sunshine to make it.

If your Crohn’s or Colitis is active, or you’re taking steroids, you should have a blood test to check your vitamin D levels. Blood tests are not helpful to check for low calcium levels, but your IBD team might check how much calcium you get in your diet instead.

You may need to take supplements if your calcium or vitamin D levels are low. Getting enough calcium and vitamin D is especially important for people who are going through menopause, or have already gone through it.

You can get calcium from dairy foods, fish with bones that you eat, broccoli, kale, spring greens and foods with added calcium, like breakfast cereal, bread and fortified plant-based dairy alternatives.

You can get vitamin D from eating oily fish, egg yolks, meat and foods with added vitamin D, like some breakfast cereals or yoghurts. But it’s hard to get enough from your diet in the winter. The Department of Health recommends that everyone over 1 year old – with or without Crohn’s or Colitis – should take 10 micrograms (10mcg) of vitamin D every day between September and March.

Some research has looked at whether vitamin D can help keep Crohn’s or Colitis under control. But there is not enough evidence to support this at the moment.

Folic acid and vitamin B12

Your body uses folic acid and vitamin B12 to make red blood cells. If you do not have enough folic acid or vitamin B12, you may get anaemia. Folic acid is also called folate or vitamin B9.

• Some people might not absorb enough folic acid from their food. This might happen if you’re taking sulphasalazine or methotrexate, you have inflammation in your small bowel, or you’ve had part of your small bowel removed.
• You might not get enough vitamin B12 in your diet if you do not eat meat or dairy foods. Or you might not absorb enough from your food if you have inflammation in your small bowel or you’ve had part of your small bowel removed.

If your folic acid or vitamin B12 levels are low, you may need to take supplements. You might have these as tablets, capsules or liquid medicine that you take by mouth. If you have anaemia due to low vitamin B12 levels, you are likely to have B12 as an injection.

You could also try to get more folic acid and vitamin B12 in your food.

• You can get folic acid from leafy green vegetables, brussels sprouts, broccoli, peas, chickpeas, beans, and foods with added folic acid.
• You can get vitamin B12 in meat, fish, milk, cheese, eggs and foods with added vitamin B12, like some breakfast cereals.

Others

Your IBD team, GP or dietitian might also check your levels of magnesium, potassium, zinc, phosphate, selenium and some vitamins.

What diets might be helpful?

We know that everyone is different and what works for one person may not work for another. It may take a while to find out what works for you.

Here, we cover some of the main diets that people ask about. Some people may find these diets helpful. But many of these diets are restrictive and they may lead to nutritional deficiencies if you follow them in the long-term.

If you decide to follow any diet to help with your Crohn’s or Colitis, it’s important to discuss it with your IBD team first. They may refer you to a dietitian. They can check that the diet is suitable for you and that you’re getting enough essential nutrients.

Low FODMAP diet

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are carbohydrates that are hard to digest. When the undigested carbohydrates pass through the bowel, they attract water. This may cause diarrhoea. They also feed bacteria in your large bowel, which release gas. This can lead to bloating and wind.

A low FODMAP diet is a three-phase diet designed to identify possible trigger foods for IBS symptoms:

• Phase one cuts out potential trigger foods
• Phase two gradually reintroduces these foods to test your response to them
• Phase three personalises your diet by unrestricting as much as possible, only avoiding your personal trigger foods

A low FODMAP diet might be helpful for people with Crohn’s or Colitis that is under control or only mildly active, but who still have tummy symptoms. These might be tummy pain, bloating, wind, diarrhoea or constipation. At the moment, though, there is not enough high quality evidence to know for sure if a low FODMAP diet is effective. More research is going on.

High-fibre diet

The theory behind a high-fibre diet is that bacteria in your gut can convert fibre into substances that may help reduce inflammation. A high-fibre diet includes lots of foods like:

• Starchy foods, such as porridge, oat bran, potato with the skin on, wholemeal or wholegrain bread and pasta
• Peas, beans and pulses, such as baked beans, lentils, chickpeas
• Fruit and vegetables

There is not enough evidence to know if a high-fibre diet is helpful for people with Crohn’s or Colitis. But fibre is important for your general health, and most people with Crohn’s or Colitis have a low intake. So if eating more fibre does not make your symptoms worse, there is no need to limit how much you eat unless you have a narrowing in your gut (a stricture).

Low residue diet

A low-residue diet limits high-fibre foods that are hard to digest, like fruit and vegetable skins, nuts, seeds and wholegrains. It also limits foods that can stay in your bowel for a while, like milk. Some people try a low-residue diet to help reduce symptoms during a flare-up. But there is no high-quality evidence that it works.

Fibre is an important part of your diet, so if you choose to follow a low-residue diet during a flare-up, it’s important to gradually increase the amount of fibre you eat when you are better.

Other diets

You may hear about other diets that some people with Crohn’s and Colitis follow. They may be helpful for some people but there has not been enough research done into their effects to say whether they work.

Crohn's Disease exclusion diet (CDED)

The CDED involves taking liquid food alongside a diet that’s high in protein and low in animal fat, gluten and additives. Over time, you reduce the amount of liquid food you have and introduce restricted foods back into your diet. It might be helpful for some people with Crohn’s, but there is not enough evidence to recommend it at the moment.

Crohn's Disease treatment with eating (CD-TREAT) diet

The CD-TREAT diet aims to get as close as possible to exclusive enteral nutrition using ordinary food rather than a liquid diet. It is high in protein but cuts out gluten, lactose, alcohol and dietary fibre. You take a multivitamin as well.

The CD-TREAT diet seems promising for people with Crohn’s. But it is still being developed and there is not enough evidence to recommend it at the moment.

Specific carbohydrate diet

The specific carbohydrate diet is a low carbohydrate diet that limits:

• Sucrose (table sugar)
• Lactose, found in dairy products
• Grains like corn, wheat, barley, oats and rice
• Starchy vegetables like potatoes and parsnips
• Beans, peas and lentils
• Most processed foods

The idea behind it is that people with Crohn’s or Colitis cannot absorb carbohydrates properly. So they pass into the large bowel, where bacteria feed on them. This may affect the balance of bacteria in your gut, which could impact your symptoms.

A specific carbohydrate diet might be helpful for some people with Crohn’s or Colitis. But there is not enough high-quality evidence to know for sure. A recent study found it was no better than a standard Mediterranean-style diet at getting Crohn’s under control and had no benefit on inflammatory markers. The diet can be difficult to follow because it limits a lot of foods.

Anti-inflammatory diet

The anti-inflammatory diet is loosely based on the specific carbohydrate diet but it does not limit as many foods. It includes probiotics and foods containing natural prebiotics to encourage gut-friendly bacteria and reduce inflammation. There has been very little research testing the diet in people with Crohn’s or Colitis. So there is not enough evidence to recommend it at the moment.

Gluten-free diet

Gluten is a protein that’s found in wheat, barley, rye and oats, or foods that contain them. Around 1 in 4 people with Crohn’s or Colitis say they are sensitive to the effects of gluten and follow a gluten-free diet. This might improve symptoms for some people, but there is not enough evidence to recommend it for everyone with Crohn’s or Colitis. A gluten-free diet is also low in FODMAPs, so it could be FODMAPs rather than gluten that are causing problems.

Mediterranean diet

A Mediterranean diet is high in fruit, vegetables, beans, pulses, cereals and healthy fats. It includes some fish and dairy products. It is low in meat and unhealthy fats.

It might be helpful for some people with Crohn’s or Colitis but there is not enough evidence to know for certain yet. There is a lot of research going on but at the moment, it is not conclusive. A Mediterranean diet is a healthy diet to follow and includes all the nutrients you need.

Semi-vegetarian, vegetarian or vegan diet

There is not enough high-quality evidence to know whether plant-based diets help get or keep Crohn’s or Colitis under control. But plant-based diets are generally healthy and are lower in fat and higher in fibre than meat-based diets. If you choose to follow a plant-based diet, try to make sure you get enough protein. You may also need to take supplements if you have any vitamin or mineral deficiencies.

Supplements

Some people take supplements or herbal remedies alongside medicines for Crohn’s or Colitis. But there is very little evidence that they help control symptoms.

Omega-3 supplements

Omega-3 is found in fish oils. Guidelines for people with Crohn’s or Colitis do not recommend taking omega-3 supplements because there is no evidence that they help.

Probiotics

Probiotics are foods or supplements containing friendly bacteria. You can buy them as drinks, yoghurts, tablets or powders. Fermented foods like kefir, kimchi, tempeh and kombucha are also probiotic.

There is no evidence that probiotics are helpful for people with Crohn’s. But, alongside prescribed medicines, they might help some people with mildly active Ulcerative Colitis get the condition under control. Some people might get side effects like diarrhoea or bloating. Probiotics might also be helpful for people who’ve had pouch surgery and have pouchitis.

There are lots of different probiotics, containing different bacteria. A type called VSL#3, which contains eight different strains of friendly bacteria, has been studied the most in Colitis.

Prebiotics

Prebiotics are high-fibre foods or supplements that your body cannot digest well. Instead, they pass into your large bowel where they feed friendly bacteria. There is no high-quality evidence that prebiotics are helpful for people with Crohn’s or Colitis.

If you choose to try prebiotics, they seem to be safe to use alongside prescribed medicines. But they can make symptoms like bloating, diarrhoea and wind worse.

Protein supplements

If you have active inflammation, your body uses more protein than usual, so you might think about using protein shakes. People might also consider taking protein supplements as part of an exercise programme. But there is not much evidence on the effect of protein supplements in people with Crohn’s or Colitis.

Protein supplements are highly processed and contain a lot of ingredients. Some of these might cause side effects if you take them for a long time. If you can, it’s better to get protein from food rather than supplements. This also helps you get other nutrients your body needs.

If you choose to use protein supplements, check the ingredients. Different supplements contain different sources of protein so choose one that’s suitable for you. It’s important to follow the instructions on the packet and mix the supplement with the right amount of water.

Herbal remedies

Some people try herbal remedies alongside prescribed medicines to help manage their symptoms. But there is not much high-quality evidence to say whether they work, or what is a safe dose. So they are not generally recommended for people with Crohn’s or Colitis.

Some herbal remedies that you might hear about include:

• Curcumin: the main ingredient of turmeric. Alongside prescribed medicines, it might be helpful for some people with Ulcerative Colitis. But more research is needed to find out the best way to take it, the best dose to use, and how long to take it. There is not enough high-quality research to know if it’s helpful for people with Crohn’s.
• Cannabis or cannabidiol (CBD): Some people say that cannabis or CBD help with symptoms. CBD is available to buy in the UK as sprays, oils, patches or tablets. But cannabis is illegal. It can also have serious side effects, especially if you take it for a long time. At the moment, we do not know enough about whether cannabis or CBD work or how much is a safe amount to take. They are not currently recommended for people with Crohn’s or Colitis.

Additives

You might have read that people with Crohn’s or Colitis should limit or avoid foods containing artificial sweeteners, thickeners, and other additives like carrageenan or titanium dioixide. This guidance is based on studies in animals. There is no high-quality evidence to say what effect additives have on people with Crohn’s or Colitis. But additives are not needed as part of a healthy diet. So if you choose to avoid them, you will not be missing out on any essential nutrients.

Changing your diet

There might be special situations when you need to change what you eat. Here, we give a brief overview, with guidance on where you can find more information.

Eating after surgery

Most people are able to get back to eating a healthy, balanced diet after surgery for Crohn’s or Colitis. If you’ve had a lot of your bowel removed and you are not able to absorb enough water or nutrients, your dietitian will advise you on what to eat to stay well.

Eating with a stoma

Most people who have a stoma can eat a healthy, balanced diet. But sometimes you might need to make some changes to what you eat.

Eating during pregnancy

If you’re pregnant or trying to get pregnant, it’s important to speak to your GP or IBD team to make sure you’re getting all the nutrients you need. It is also recommended that you take:

• 400 micrograms (400mcg) of folic acid daily from before you get pregnant until you are 12 weeks pregnant
• 10 micrograms (10mcg) of vitamin D daily throughout your pregnancy

Children with Crohn’s or Colitis

Children and teenagers need more nutrients per kilogram of body weight than adults to help them grow. Your child’s IBD team will check whether your child is absorbing enough nutrients from their food. If not, they might recommend supplements. If your child has Crohn’s, their IBD team might recommend a liquid diet (exclusive enteral nutrition) for 6 to 8 weeks to get their condition under control.

Eating when your immune system is low

If you are on medicines that lower your immune system, you might not be able to fight off infections as well as other people. To lower your risk of getting infections spread through food, it’s important to store and prepare food safely. And wash your hands before preparing or eating food.

Fasting

There is very little evidence on the effect of intermittent fasting or time-restricted eating on Crohn’s or Colitis. Intermittent fasting for religious reasons, such as during Ramadan, does not usually cause problems for most people with Crohn’s or Colitis. But some people might find their symptoms get worse. Your IBD team might advise you not to fast if:

• You are losing a lot of fluid, for example, from a high-output stoma or ongoing diarrhoea
• You are low in nutrients
• You are in a flare-up
• You take medicines by mouth during the day

Eating out

Up to 1 in 4 people with Crohn’s or Colitis say they avoid eating out because it is hard to control what food they’re eating. If you would like to eat out but you have particular dietary needs, let the restaurant know. It’s OK to ask about ingredients or how things are cooked. Some people find it helpful to explain that they do not have an allergy, but that some foods could trigger serious symptoms. You could contact restaurants beforehand to find out if they can meet your needs.

You might find a food diary or app helpful when you’re speaking to your IBD team or dietitian about your diet. It can also help show whether you’re getting enough nutrients or if any foods may be triggering your symptoms. It’s important not to make any changes to your diet without speaking to your IBD team or dietitian first.

If you use a food diary or app, try to note everything you eat and drink. Include details like whether you had brown or white rice or how your food was cooked. You may find it easier to identify possible trigger foods when your condition is under control and you’re not in a flare-up.

We follow strict processes to make sure our information is based on up-to-date evidence and easy to understand.

Please email us at evidence@crohnsandcolitis.org.uk if:

• You have any comments or suggestions for improvements
• You would like more information about the sources of evidence we use
• You would like details of any conflicts of interest

You can also write to us at Crohn’s & Colitis UK, 1 Bishop Square, Hatfield, AL10 9NE, or contact us through our Helpline: 0300 222 5700