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Food Intolerances associated with IBS

Most recent research on the dietary management of IBS in Australia has been focused on fermentable carbohydrates, which are a group of dietary sugars that have been termed FODMAP™s. This is an acronym for Fermentable Oligo-saccharides, Di-saccharides, Mono-saccharides and Polyols. Current research suggests that this group of sugars can contribute to IBS symptoms. Studies have found that a diet that restricts these sugars can improve IBS symptoms in many people. Dietary restriction of these poorly absorbed sugars requires advice from a dietitian specialising in gastrointestinal nutrition. In general a dietitian will advise you to trial a Low FODMAP™ diet for a period of 6-8 weeks, they will then review your progress and advise you on how much of certain foods can be safely added back into your diet.

How do FODMAPs cause symptoms in people with IBS?

When food is consumed it passes from the mouth into the stomach, where it mixes with gastric secretions to break the food down into a form that can pass into the small bowel. In the small bowel the nutrients are further broken down for absorption into the blood stream. All undigested nutrients and waste products continue along the bowel and enter the large bowel (or colon). The large bowel’s role is to absorb water and prepare undigested food for removal from the body as faeces. The large bowel contains a large number of bacteria which ferment undigested nutrients from food, which can result in the production of gas and excessively liquid stools. This can cause a change in motility in the bowel due to bowel distention, which can result in symptoms of diarrhoea, bloating, abdominal pain or sometimes constipation. Carbohydrates that are poorly absorbed in the small bowel will product these symptoms and this is often the case for people with IBS.

Restriction of particular FODMAP™s in people with IBS may be beneficial and a Dietitian specialising in the area can advise you on this.

Further Information on Food Intolerances:

  • What are FODMAP™S?

    What are FODMAP™S?

    Fructans and galactans – Are a chain of sugars called oligosaccharides and humans cannot break these down in the small bowel, so they are broken down by bacteria in the large bowel, resulting in gas production. These are found in several foods including wheat, rye and some fruits and vegetables.

    Sugar polyols – These are sugar alcohols such as sorbitol and mannitol, they are not completely absorbed in the small intestine in all people. When they are eaten in excess they can contribute to diarrhoea. These are found naturally in some fruits and vegetables as well as in artificial sweeteners.

    Fructose - Fructose in a single sugar unit, known as a monosaccharide. Around 40% of healthy individuals and people who suffer from IBS cannot absorb excessive fructose. If people with IBS are found to be malabsorbing fructose they should avoid it. Fructose is found in some fruits and vegetables and honey, as well as many processed foods.

    Lactose - Contains two sugar units joined together and is known as a disaccharide. Lactose is a sugar found in milk. In those who are lactose intolerant, the cells lining the small bowel do not produce enough of the enzyme lactase needed to break down lactose. In this case lactose reaches the large bowel undigested and the bacteria in the colon feed on the lactose, which producing symptoms of diarrhoea, bloating, abdominal pain, and gas.

    How are Fructose or lactose malabsorption diagnosed?

    Fructose and Lactose malabsorption can be diagnosed by breath testing , but often restriction of lactose alone or a ‘challenge’ with milk can make the diagnosis of lactose intolerance without the need for a breath test.

    A breath test measures the amount of hydrogen and methane gas in the breath after swallowing a measured amount of fructose or lactose. If these sugars are poorly absorbed, the intestinal bacteria break down the sugar to produce either hydrogen or methane.

    A rise in breath hydrogen or methane confirms the test sugar has been malabsorbed. This indicates that a dietary restriction of fructose and/or lactose would be beneficial to assist in the management of symptoms. It is important to note that other FODMAPs cannot be tested for and therefore these need to be discussed with your dietitian.

    Food Chemicals and elimination diets:

    There is some evidence that supports that food chemicals sensitivity can contribute to symptoms of IBS. These include amines, salicylates and glutamates, which are found in a wide range of foods. These food chemicals have been associated with eczema, respiratory symptoms (e.g., Asthma or hayfever), migraines, mouth ulcers, and gastrointestinal symptoms.

    Testing for food chemical sensitivity is very difficult. The only way of determining food chemical sensitivity is though following an appropriate elimination diet. This is a very involved process and requires a very experienced dietitian to provide guidance. It generally involves maintaining a very strict diet to avoid foods that are moderate or high in food chemicals for a period of about 2-4 weeks. If there is no change in symptoms over this time the diet is stopped and a normal diet resumed. If there is an improvement, then the excluded foods with particular chemicals in them are individually re-introduced back into the diet one at a time.

    During this time it is often recommended to keep a food diary with a clear description of food/drink consumed, emotional state, and menstrual cycle, to gain an understanding of what is triggering the symptoms. Although an elimination diet can be useful in identifying food chemical sensitivity, it is very difficult to follow. Most often meals have to be prepared from scratch, shopping takes longer as all food labels must be checked, and finding suitable snacks and eating out can be inconvenient and difficult. This diet should not be attempted without the advice of a dietitian.

    Elimination diets can lead to a severely unbalanced diet or an obsessive preoccupation with food, and should therefore only be conducted under supervision of a doctor and dietitian.

  • Dietary Recommendations for IBS patients

    Dietary Recommendations for IBS patients

    Before starting any strict diets to investigate food intolerances it is important to get the basics right. A dietitian is best person available to assess your individual diet and advise you on what changes you can make and whether or not you should trial a low FODMAP diet or an elimination diet. Unnecessary dietary restriction is not recommended.

    Basic dietary guidelines for IBS:

    • Have small meals at regular times throughout the day, this is easier for the digestive system to handle than one big meal. A large meal can cause stronger muscles contractions in the digestive tract, resulting in abdominal discomfort, heartburn and nausea. Long periods of fasting can also increase gastric acid secretion, which can increase symptoms
    • Always make time for breakfast
    • Make your evening meal the lightest of the day, and try to eat earlier to give your body time to begin digesting food before going to bed
    • Never rush a meal- eating quickly and rushing meals can lead to air being swallowed at the same time. This can result in belching and heartburn, and can cause bloating and wind
    • Sit down to eat, and sit up straight when eating
    • Concentrate on what you are eating and chew food thoroughly. This will help prevent you from eating too fast and swallowing air
    • Avoid chewing gum, as it causes you to swallow excess air as well as adding excessive amounts of sugar polyols to your diet
    • Drink adequate amounts of fluid through throughout the day, this is particularly important for people with constipation. The daily recommendations for fluid are between 2-3 litres per day, depending on your activity levels and weight
    • Avoid large amounts of carbonated beverages

    Avoid large amounts of common trigger foods:

    Fat: Fat can be a major trigger of symptoms in IBS patients. This is because fat is difficult to digest and it requires the greatest amount of enzymes to break it down. Fat is the strongest activator of intestinal contractions and increases sensitivity of the intestine. It is therefore recommended that IBS sufferers reduce their fat intake.

    This means limiting foods such as, fried foods, cream, rich desserts, large amounts of cheese, chocolate, and fats and oil in cooking. Limiting fat produces health benefits beyond improvement of digestive symptoms for all people, including reduced risk of developing high blood cholesterol, heart disease, stroke and certain types of cancer.

    How much fat are you eating in a day?

    You should aim for no more that 60-70g of fat per day, which is approximately 30% of your energy intake coming from fat in your food. Record your days food intake and calculate the amount of fat you are eating using.

    Caffeine: Caffeine stimulates the digestive system. This can lead to strong contractions, increasing bowel movements and exacerbating IBS symptoms, especially abdominal cramping and diarrhoea. Caffeine also has a diuretic effect, which can worsen dehydration caused by diarrhoea. Caffeine is found in coffee, tea, cola beverages, and chocolate. Keep caffeinated foods to no more than 2 serves per day.

    Alcohol: Alcohol is irritating to the digestive system, and can trigger IBS symptoms, especially diarrhoea, abdominal discomfort, and heartburn. Alcohol is also dehydrating to the digestive tract. If you do drink alcohol, always accompany it with some food. Alcohol should be limited to no more than 1-2 standard drinks.


    Many people with IBS are often recommended to increase their fibre intake. This should be done with caution. There is limited evidence that this approach provides any benefit to people and in some instances it can make symptoms worse. Many patients with IBS are taking large amounts of fibre, and may even benefit from a reduction in fibre intake

    Fibre is critical to our digestive tract, as it regulates the rate at which food moves through the gut, and adds bulk to stools and helps stimulate bowel motions.. The daily recommended fibre intake is 30g per day, diet containing greater than this amount are not recommended for the management of IBS and may lead to increased symptoms.

    Fibre comes from fruit, vegetables and grains. There are different types of fibre that are found in our food and they behave differently in the gut, these include soluble fibre and insoluble fibre.

    Soluble fibre – Is found mainly within plant cells, good dietary source include fruits, vegetables, oat bran, barley, seed husks, flaxseed, psyllium, legumes and soymilk products. Soluble fibre soaks up water like a sponge, which helps to bulk up the faeces and allows it to pass through the gut more easily. It can also act to slow down the rate of digestion. It can be beneficial in constipation and/or diarrhoea. For patients with IBS, soluble fibre has been found to be more beneficial, but can be rapidly fermented and may increase symptoms in some patients. Psyllium is a good choice if a fibre supplement if required.

    Insoluble fibre – Is the structural parts of plant cell walls. The major role of insoluble fibre is to add bulk to faeces and to prevent constipation. Insoluble fibre cannot get broken down by digestive enzymes in the small bowel and it passes into the large bowel relatively unchanged. It doesn't absorb water and speeds up the time that food passes through the gut. Good sources include wheat bran, corn bran, rice bran, the skins of fruits and vegetables, nuts, seeds, dried beans and wholegrain foods. Large amount of insoluble fibre particularly from wheat bran does not benefit people with IBS and in may make symptoms worse.

    If you have a low fibre diet it would be beneficial to trial increasing your fibre intake, particularly of soluble fibre. This should be done gradually to avoid increasing symptoms. Also when you are increasing amounts of fibre in your diet it is also important to drink plenty of fluids, and increase the fibre slowly.

    How much fibre are you consuming?

    You should aim for approximately 30g of fibre per day. Record your days food intake and calculate the amount of fibre you are eating using Calorie King.

    Complex dietary Changes:

    If the above simple dietary changes are not sufficient to manage your symptoms of IBS then it would be reasonable to trial a low FODMAP diet, with the guidance of a dietitian.

    Before considering removing any foods from your diet it is recommended that you have been seen by a gastroenterologist and other gastrointestinal conditions have been ruled out and you have a clear diagnosis of IBS.

    At this point a food and symptom dairy can be useful to help you and your dietitian to identify triggers and then provided you with recommendations on what dietary changes will assist you with your IBS management

    A low FODMAP diet may be recommended depending on your specific symptoms and intolerances. This will involve avoiding high FODMAP foods.

    High FODMAP foods include:

    Fructose: Asparagus, artichokes, sugar snap peas, legumes, apples, pears, cherries, mango, nashi, tined fruit in natural juice, honey, high fructose corn syrup. Also all concentrated forms Eg: dried fruits, fruit juice and large fruits salads.

    Fructans and galactans: Artichokes, asparagus, beetroot, chicory, garlic, onions, wheat (in large amounts), rye (in large amounts), Inulin, Fructo-oligosaccharides.

    Sugar polyols: Apples, apricots, avocado, cherries, longon, lychee, nectarines, pears, plums, prunes, mushrooms, sorbitol, mannitol, xylitol, maltitol and isomalt.

    Lactose: lactose is the sugar found in dairy foods. Foods high in lactose are cow’s milk, frozen, yoghurt, yoghurt, ice cream, and milk chocolate. Also soft cheese when consumed in large amounts will contain significant amounts of lactose. Other dairy foods do not have significant amounts of lactose and can be tolerated, these include butter, margarine and hard cheeses. It is important to note that people with lactose intolerance do not need to exclude dairy altogether from their diets. Many people can tolerate small amounts of lactose rich foods (e.g. regular milk with cereal or in tea/coffee). There are also lactose free alternatives available, including lactose free milk and yoghurt, containing all the nutrients found in regular products.

    This is not a comprehensive guide to the management of a low FODMAP diet, it is best to see a dietitian specialising in the area of gastrointestinal nutrition to clearly explain diet and make individual recommendation.

  • Food Chemical Sensitivity

    Food Chemical Sensitivity

    As previously mentioned food chemicals can be a cause of IBS symptoms and a comprehensive elimination diet is required to determine if this is the case. A dietitian who specialises in the area is the best person to advise you of this.

    High Chemical foods:

    Amines: come from protein breakdown or fermentation. Large amounts are present in flavourings used for cereals, dairy products and snack food, cheese, nuts, chocolate, wines, beer, soft drink, fruit juice and cordial, yeast extracts, soy sauce, tamari and miso, coconut milk and cream, some processed meat products (pork, bacon, ham, sausages, salami, offal and chicken skin) and most seafood and fish products (except white fish, calamari and sea scallops). They are also found in some fruits (most except pears) and vegetables (not all vegetables, salicylates are more common) e.g. bananas, avocados, tomatoes and broadbeans.

    Salicylates: are a family of plant chemicals found naturally in many foods, many foods will have a combination of Amines and Salicylates. The foods high in Salicylates include many fruits (most except pears), many vegetables (most except a sort list including white potatoes, Swede, Brussels spouts, cabbage, celery, lettuce, green beans, leeks, garlic and legumes), corn and corn products, jasmine or wild rice, processed meat (salami), nuts and flavoured chips, herbs and spices, flavoured dairy products, coconut milk or cream, jams, honey, yeast extracts, tea and coffee, fruit juices and cordials, soft drinks, beer and wines. They are also present in flavourings (e.g. peppermint), perfumes, scented toiletries, eucalyptus oils, and some medications, such as Aspirin.

    Glutamates: are the building blocks of all proteins, and are found naturally in most foods. Foods rich in natural glutamate are used in many meals as it enhances the flavour of the food. For example Flavoured or coloured snack food and cereal based products, cheeses, Processed meats (salami, sausages, pressed chicken, mushrooms, stock cubes, sauces (gravy, fish sauce, say sauce, tamari), meat extracts and yeast extracts, tomato sauce and juice and pickles. Pure monosodium glutamate (MSG) can also be used as an additive to increase the flavour of soups, sauces, Asian cooking and snack foods.

    Dietary Recommendation for IBS-Subtypes

    • Increase soluble fibre
    • Avoid high fat foods
    • Avoid artificial sweeteners
    • Avoid alcohol
    • Avoid caffeine
    • Consider Lactose and fructose intolerance
    • Consider Low FODMAPs
    • Increase fibre – particularly soluble fibre
    • Increase water
    • Increase exercise
    • Consider low FODMAPs

  • General Guidelines for Healthy Eating

    General Guidelines for Healthy Eating

    General healthy eating is important to ensure you get all the vitamins, minerals and energy your body requires to repair itself, to keep bones, teeth and organs healthy, to perform activities, to enhance mood and concentration, and to maintain a healthy weight. It is a good idea to choose less refined foods as processed foods are more likely to have added salt, sugar, saturated fats, preservatives, and artificial colouring. Furthermore, processed foods often have very few vitamins and minerals, as these are removed to give foods longer shelf life.

    The current Australian dietary guidelines are below: This aims to provide you with adequate amount of energy, protein, vitamins, minerals and fibre to promote health and avoid disease.

    Enjoy a wide variety of nutritious foods:

    • Eat plenty of vegetables, legumes and fruits
    • Eat plenty of cereals (including breads, rice, pasta and noodles), preferably wholegrain
    • Include lean meat, fish, poultry and/or alternatives
    • Include milks, yoghurts, cheeses and/or alternatives. Reduced-fat varieties should be chosen, where possible
    • Drink plenty of water

    And take care to:

    • Limit saturated fat and moderate total fat intake
    • Choose foods low in salt
    • Limit your alcohol intake if you choose to drink
    • Consume only moderate amounts of sugars and foods containing added sugars.

    Prevent weight gain: be physically active and eat according to your energy needs

    The following is a basic guide to a healthy balanced diet:

    1. Bread and cereals: At least 4-8 serves per day

    • 1 slices of wheat free bread
    • 1 cup of wheat free cereal
    • ½ cup of gluten free pasta/porridge/ rice

    2. Fruits: At least 2 serves per day

    • 1 medium piece of fruit

    3. Vegetables: at least 5 serves per day

    • ½ cooked vegetables
    • 1 cup of salad

    4. Milk or milk alternatives: 3-4 serves per day

    • 1 cup of milk or alternative
    • 200g yoghurt or alternative
    • 40g of cheese

    5. Meat or meat alternatives: 1-2 serves per day

    • 75-100g cooked meat, chicken
    • 120-150g of fish
    • 2 eggs

    6. Fluid: Drink at least 8 cups of fluid per day: water is best

    A food pyramid provides an easy way to remember the healthiest way to eat. It groups foods together according to their energy content and according to the various nutrients that they can provide. The largest portion of our diet should come from the base of the pyramid, which includes unprocessed foods such as fruit and vegetables, nuts, grains and cereals, breads, legumes and beans. These foods contain many different nutrients and should make up most of the food that we eat.

    In the middle of the pyramid are foods we can and should eat, but not excessively. These foods provide us with protein, minerals such as iron and calcium, and vitamins. These foods include fish, lean meat (with the fat removed), dairy products, eggs and chicken.

    The top of the pyramid are foods we should minimise, these foods have fewer nutrients and can contribute large amounts of energy to the diet which can cause weight gains and put you at risk of heart disease and diabetes. These foods include fats, sugar and oils


If you are interested in other gastrointestinal-focused information and intervention websites developed and hosted at
Swinburne University of Technology,
please go to:

IBDclinic.org.au for individuals with Inflammatory Bowel Disease

Gastroparesisclinic.org for individuals with Gastroparesis


This website and its content is not intended or recommended as a substitute for medical advice, diagnosis or treatment. Always seek advice of your own physician or other qualified health care professional regarding any medical questions or conditions.

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