There is no easy way to identify which food if any is causing the IBS symptoms

Diet for irritable bowel syndrome

• Irritable bowel syndrome has no definable cause but there are clearly some triggers that aggravate the condition.
• The main triggers are:
  • Stressful life events.
  • Food triggers.
  • Gastroenteritis infections - can be the starting event or an aggravating factor
• Altering the diet is always going to be the easiest approach to reducing these "triggers" but approaches towards reducing stress should also be explored.
• The majority of food triggers are best described as an intolerance rather than food allergy.
• Genuine food allergy as a cause of IBS is probably uncommon.
  • Food allergy causes rapid onset of itching, swelling of lips, tightness in throat and wheezing.
  • 90% of food-related allergic problems are caused by  milk, eggs, peanut, soy, other nuts, fish, shellfish.
• The mechanism by which foods aggravate IBS is unclear.
  • It probably involves events in the lumen of the bowel rather than any inflammatory or immune response of the bowel wall.
  • This means that the symptoms may be due to foods that were consumed over the past 1-3 days - not just the last meal.
  • "Intolerance" may occur for larger helpings of a particular food but not with smaller amounts. This is different from a genuine allergy where even small amounts can cause symptoms within a few hours.
  • Colonic fermentation is probably an important mechanism. This depends on the type of bacteria in the colon AND the type of food AND the speed of transit through the colon.
  • Fermentation and gas production is increased in people with irritable bowel.
• For example the exclusion of wheat from the diet is a common recommendation (and is often helpful).
  • This benefit can be demonstrated in people who do not have the immune-based disease of coeliac disease (gluten-sensitive enteropathy).
  • The mechanism by which wheat aggravates IBS is debated - it may be because of higher fermentation levels (gas production) in the colon with wheat compared with rice.
  • Increased levels of gas production in people with IBS is a problem because the gut more sensitive to "stretch" from trapped wind
  • There may be other mechanisms by which gluten can exert harmful effects on the gut (different from the immune-mediated coeliac disease and not related to excess fermentation) but more research is required.
  • It is seems likely that a low carbohydrate diet is effective  - this is a more radical approach and could have some long-term harmful effects  i.e higher risk of heart disease if animal fats and protein are markedly increased. 
• The most diets that have been developed for IBS have come from extensive questionnaires rather than from any direct scientific study.
  • There is no easy shortcut to finding out what are the aggravating foods. Skin prick tests and blood tests for allergy have proven to be disappointing.
  • The suggestions for "allowed" and "not allowed" (in the exclusion table are simply those foods that are prominent in dietary surveys of people with IBS.
  • The recent promotion of a FODMAP diet is partly driven by science  - that is careful analysis of food composition looking for poorly absorbed carbohydrates.  The concept is that this "normal" malabsorption is a key mechanism in IBS by caused distension of the bowel and pain in a bowel that is over-sensitive (a hallmark of IBS) and diarrhoea by the osmotic effect of poorly absorbed carbohydrate.
  The strict approach for any exclusion diet is too have a very restricted diet for 2-4 weeks and then gradually add in foods one by one or perhaps by group (in the FODMAP diet).  This is straightforward concept but difficult too achieve in practice. The underlying variability of IBS makes any improvement or deterioration difficult to interpret. These negative and discouraging comments shouldn’t detract from the main message.
• Food triggers are common.
• If identified, exclusion of particular foods can make a long-term difference to quality of life with IBS.
• Food exclusion is always a more preferred option to taking prescribed medications for IBS.

• The main risk from an exclusion diet is developing an inappropriately strict approach to food exclusions that may not necessarily to be required. Other risks  - real and theoretical include
  
  • Weight loss - mostly good, occasionally entering into hazardous low weight
  • An unhealthy obsession with what can and can't be consumed.
  • Heightened stress with regard to food choices.
  • Low risk, but possibly nutrient deficiency
  • Changes in faecal micrbiota that theoretcially could be harmful in the long term
• There are some foods that cause problems for most people with IBS but there are also unique issues for any individual.
  
  

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Recommended recipe book

• Low FODMAP cooking book available from www.shepherdworks.co.au
• "The two step guide to a low FODMAP diet and recipes by Sue Shephard
• Written by one of the original investigators into the low FODMAP diet  - Melbourne, Australia
• Monash university low FODMAP diet is the recommended app for a comprehensive diet guide and also some recipes

Exclusion diets can still be tasty!!

Exclusion diet

• The table below is a suggested list of allowed and not allowed foods in each major food group.
• This table comes from recommendations based on extensive questionnaires and some clinical experience
• There are major similarities with the FODMAP diet which is now widely promoted for IBS.  I have keep much of this information rather than replacing completely with the low FODMAP diet as there is more to the diet question in IBS than just FODMAPs
• Hopefully you will find some general advice helpful and additional to advice that can be obtained from low FODMAP websites
• If a strict exclusion diet approach sounds too difficult then simply scan through the suggested exclusion.
  • Pick out some foods that seem to be possible “triggers” in your case.
  • Remember it can take 2-4 weeks of exclusion before any clear trends emerge
  • Dairy food intolerance in IBS is not universal - maybe 15-25% of people gain some benefit from being dairy-free (see section - lactose intolerance)

Is fibre good for you? Maybe - but wholegrain breads cause bloading and wind and aggravate symptoms for many people with IBS

Try the rice bread by Vogels

Dietary Fibre - the benefits and disadvantages

• Dietary fibre is the part of the plant which passes through mostly undigested into the large bowel (colon).
• Fibre may be soluble or insoluble.
• Some starch can be considered in the same category as fibre because it is resistant to digestion (resistant starch).
• Soluble fibre can help to lower cholesterol although the effect is relatively small.
  • If you have a raised cholesterol then oat bran is not going to resolve the issue. You may need cholesterol lowering drugs, low fat diet, weight loss and attention to other risk factors such as high blood pressure and stopping smoking.
• Soluble fibre is found in;
  • Oats.
  • Legumes (dried peas, beans, lentils).
  • Nuts.
  • Most fruits.
  • There is some fermentation by colonic bacteria. This may produce beneficial effects on the colon – such as the formation of special fatty acids (butyric acid) but also may form unpleasant wind.
• Insoluble fibre is more resistant to digestion and creates less wind.
  • It is more difficult to find dietary sources.
  • Fibre supplements such as Normacol are one option.
• Resistant starch is found in
  • Cereals, vegetables and fruit.
  • It can also form after cooling of cooked potatoes.
  • Maize flours (corn) contain lots of resistant starch.
  • Benefibre is a commercial product used for constipation but does cause extra wind.
• Too much fibre will cause excessive wind and abdominal bloating.
  • Some fibre types are more likely to cause wind. Beans and lentils are particularly prone to aggravate wind.
  • Whole grain breads may cause wind. Brown rice is OK.
  • If you have irritable bowel syndrome increasing fibre intake may actually aggravate your symptoms. There has been too much emphasis on increasing dietary fibre with IBS.
  • Many people with IBS (perhaps 2/3 rds) are actually worse with increased fibre.
  • There is no value in taking fibre if diarrhoea is the main problem.
  • If constipation is the main problem then dietary fibre can be helpful because the fibre absorbs water and softens the bowel motions.

• Fibre supplements.

  • Available to purchase from the chemist.
  • These are based on natural plant extracts - physillium or sterculia.
  • Normacol (insoluble fibre) may have less wind production however this is less palatable than the dissolving forms of fibre (Metamucil and Mucilax).   Granules can be taken on cereal, mixed with yoghurt etc.
    
    
  • In general I don't recommend fibre supplements or any attempt to increase dietary fibre because bloating can be unpleasant and aggravate pain
  • A low FODMAP diet can cause constipation  - relief of this problem may be best managed with kiwifuit or magnesium capsules
• It is proposed that dietary fibre may decrease the risk of diverticular disease and bowel cancer but these are unproven concepts.

Coffee is a great drink - but probably the top offender for many people. Coffee causes urgency and frequency and also increases abdominal cramps

What is good to drink? Tea is better than coffee. Peppermint tea has some anti-spasm effects

Good vegetables are lettuce, spinach, green beans (sliced), pumpkin, carrot, avocado, tomato, zucchini.

Important aspects of the exclusion diet

• The crucial part of an exclusion diet is a change in carbohydrate intake from wheat to rice.
• Rice seems to be well tolerated by most people with IBS.  A low carbohydrate diet has been shown to helpful in a small study. 
  
  
• This may not need to be an absolute change to achieve an effect. If bloating or excess flatulence is a prominent symptom then this change is likely to be very helpful.
• It is important to check the supermarket for rice-based substitutes. Fortunately these are much more readily available now (including rice flour, rice flakes, ground rice -used for puddings, crumble topping, biscuits).
• A gluten-free diet is a more difficult dietary change.  Most of the benefit from a gluten-free diet relates to a reduction in fermenetable carbohydrates.  At this stage it is not my recommendation to have a strict gluten-free diet but I do commonly see patients who have had a good response.  Their usual question is low long do I need to maintain this diet and how strict do I need to be!
• It is not possible to give any evidence-based answer  - other than trial and error
• Gluten-free bread may not always be beneficial in IBS because the substitutes for wheat, barley and rye may still be wind-producing (ie. corn and soya flour). The best carbohydrate source by far is rice.
• The other types of flour may be worth trying -   the health food shop is particularly useful for other less common substitute cereals.
  • Arrowroot - resembles cornflower – can be used as thickener for gravies.
  • Buckwheat - useful for coating fish.
  • Carob flour - used to flavour drinks or biscuits - “chocolate” taste.
  • Sago - useful for puddings or as a thickener.
  • Quinoa - similar to rice.
• Some vegetables are particularly wind forming.
  • The cabbage family (cabbage, brussel sprouts, broccoli, cauliflower, asparagus) contain a sugar called rabbinose. This is poorly absorbed and causes increased fermentation. I tend to encourage broccoli as this vegetable has some possible anti-inflammatory activity and range of anti-oxidants (this may outweigh any potential "wind" issues). The FODMAP diet suggests avoiding the stalks.
  • Onions and garlic are well known culprits.
  • Beans cause gas! (in particular baked beans). Bean salads and lentils (split peas) can cause problems.  If soaking overnight discard water and use fresh water. Sliced green beans are OK.
  • Resistant starch is wind-forming. It is found in cold cooked potatoes, reheated pasta, green bananas.
  • Other wind-forming foods are some nuts (almonds and cashews - peanuts may be OK). Most seeds are OK including LSA
  • Sorbitol is found in some sweets, diabetic drinks and jams and should be avoided.

General tips

• Lunches are a particular problem especially if eating on the run.
  • Many people feel bloated after lunch.
  • I advice against a sandwich or filled roll as the bread can be a problem.
  • Rice is good – sushi or leftover fried rice or rice crackers can be tried.
  • No carbohydrate at all may be best - try tuna with lettuce salad or soups.
• If diarrhoea is a major problem.
  • Coffee should be stopped completely.  This has a profound stimulant effect on the colon causing looseness, urgency and abdominal cramps. Decaffeinated coffee may not be much better. Tea is OK but herbal tea or water is best.  There may be some withdrawal headaches during the following 2 weeks after stopping coffee
  • Alcohol should be avoided. Wine may be the worst culprit but all alcohol may cause a tendency to diarrhoea.
  • Spicy foods may cause diarrhoea.
• Some sugar substitutes in diet foods may cause problems (sorbitol and xylitol).
  • Sorbitol is found naturally in fruits including apples, pears, peaches, prunes.
  • Xylitol or sorbitol is present in diet chewing gums and diet sweets. Also in regular sweets, low calorie ice-cream, diet yoghurt.
  • There are many different sugar alcohols. Beware of anything that ends in "ol" !!!  All of which can cause GI symptoms because of poor absorption (Isomalt, lactilol, maltilol, mannitol, lactalol).

Foods with high fructose

Foods to avoid

Very useful guide to a FODMAP diet. Much better than a website or book as it is easy for quick reference when preparing a meal

OK foods

Low FODMAP diet

• Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols
• These are short chain carbohydrates and sugar alcohols that are poorly absorbed by the body.
  

The principle of the low FODMAP diet is the reduction in poorly absorbed carbohydrates to reduce fermentation and hence intestinal gas as well reduce the osmotic effect of these carbohydrates that may cause diarrhoea.

The main Monosaccharide to consider is fructose. The other Disaccharide to consider is lactose (discussed in next section).

Fructose malabsorption

• Some people are not able to handle excess amounts of fructose.
  • A degree of fructose intolerance is common
  • Up to 2/3 rd of healthy people with no bowel symptoms can be shown to have some problems absorbing fructose by breath testing. This can be an issue if you have IBS as any consequent wind formation or tendency to diarrhoea caused by fructose (that is not absorbed) will cause symptoms
  • Fructose is becoming a popular food sweetener for a variety of manufactured foods. e.g in muesli bars. It can be made cheaply from corn syrup (HFCS - high fructose corn syrup.  Starch is enzymatically converted to 70% fructose). There are a wide variety of products that may contain HFCS - sweetened yoghurts, salad dressing, jams, ice-cream, canned fruit, sweets, carbonated drinks, brreakfast cereal etc.  It may be that sugar is more commonly used in NZ but this trend is hard to monitor and depends on the relative costs of these sweeteners.
  • Sucrose (common sugar) is 50% fructose and 50% glucose.  In general fructose is absorbed 1 for 1 with glucose but this mechanism can be overwhelmed by a high sugar diet
  • Fresh fruits are obviously a healthy food item but unfortunately in excess may aggravate IBS.
  • Fructose is also ingested in more complex forms - fructans (chains of fructose),
• A fructose breath test has been promoted as a way of predicting who will respond to a low FODMAP diet.  In practice over70% of people with IBS have a positive test and this has minimal predictive value
• The full FODMAP involves significant attention to detail and should have supervision by a dietitian.  Nutritional deficiencies could develop if used long-term without supervision
• Food to avoid if fructose intolerance is suspected.
  • High fructose fruits - pears, apples, plums, apricots, peaches, watermelon (low fructose fruits are bananas, mandarins, oranges, grapes, strawberries, blueberries, rhubarb, passionfruit, papaya and pineapple).
  • Concentrated fruit juices (particularly apple juice) and dried fruit will have a high fructose load  - more than eating fresh fruit
  • Honey (almost pure fructose).
  • Onions, wheat (contain fructans).
  • Carbonated drinks - Coke,Sprite etc.
  • High fructose corn syrup (sometimes just labelled as HFCS) - common additive in muesli bars and other snack foods, many processed and canned foods. 
• Breath testing for fructose malabsorption has been promoted as a way of predicting who will respond  to a low FODMAP diet  - actually only 60-70% of people will respond.
  
  • The evidence is mixed but mostly not in favour of breath testing. The breath test is cumbersome and the results unreliable
  • Most people with IBS should have a trial of the low FODMAP diet
  • People with prominent bloating, excess wind and diarrhoea will have a better response

Oligosaccharides (fructans and galactans)  - the "O" in FODMAP

• Fructans have been discussed above - chains of fructose. These are largely undigested and pass into the large bowel unchanged
• Galactans (chains of galactose with a glucose at the end).  These are also largely undigested and contribure to bloating by fermentation of colonic bacteria
• This carbohydrate is found in legumes, baked beans and kidney beans, lentils, chickpeas, split peas

Polyols  - the "P"

• Natural polyols are sorbitol and mannitol
• Foods high in polyols are apples, apricots, nectarines, pears, plums, prunes, mushrooms
• Food additives / sweetener.  Check food labels carefully.  Packet fruit-flavoured drinks Any food with sorbitol (420), mannitol (421), xyitol (967), maltilol (965) and isomalt (953) should be excluded

Lactose Intolerance (benefit of a dairy-free diet)

• Dairy products contain the milk sugar lactose.
  • Some people are unable to digest lactose because they lack the enzyme lactase which splits the lactose into in parts (galactose and glucose).
  • Lactose is also added to many commercial foods e.g salad dressings, bread, cereals.
• Lactose that is not digested enters the colon and is fermented by the action of bacteria in colon. This produces;
  • Wind (bloating and flatulence).
  • Loose bowel motions.
  • Abdominal cramps as a result of the distension from increased gas production.
• A lack of the lactase enzyme.
  • Is more common in Asian, African and Middle Eastern populations.
  • Temporary lactose intolerance is common after a gastroenteritis illness.
  • Persistence of the lactase enzyne (beyond the first two years) is actually the mutation  - disappearance of enzyme once breastfedding is completed in the "natural" or oldest state. 
• Lactose intolerance is not the same as having irritable bowel syndrome.
  • But may be an aggravating factor for some people with IBS.
  • The contribution of lactose intolerance to IBS in general is debated and may vary from country to country.
  • Perhaps 15-25% of people with IBS will gain some benefit from a dairy-free diet (but there is little data in this area).  Many who improve actualy have normal lactase levels
• The association of symptoms with dairy food intake may not be obvious and there will need to be a one-month trial of dairy food exclusion to see if there is any improvement.
• There are tests available for testing the level of lactase enzyme activity.
  • The most accurate test is a hydrogen breath test. This requires the collection of a sample of exhaled air every 30mins over a 3-hr period after having ingesting a large amount of lactose. Some symptoms may be caused by the lactose load if there is a genuine intolerance.
  • The other method is to take a biopsy sample from the small bowel (duodenum) at the time of a gastroscopy (in practice this has proved to be less accurate because the biopsy needs to be delivered to the laboratory quickly and assayed without delay to measure activity of lactase and 2 other disaccharides - maltase and sucrase.  Deficiency of maltase and sucrase is rare - if all three enzymes have low activity it is more likely that the smale was degraded before assay
• Usually I favour the pragmatic approach of trying a dairy-free diet rather than trying to prove a problem with lack of lactase enzyme.
  • In general it is usually the lactose levels in dairy foods that determines intolerance.
  • BUT there are probably other parts of dairy products that can also cause symptoms.
• General tips for reducing lactose in the diet.
  • Soft cheese have much more lactose than hard cheese.
  • Lactose levels in yoghurt are generally low. They are often tolerated when other dairy foods give symptoms.
  • The presence of the "good bacteria" L.acidophilus and Bifidobacterium in natural yoghurt may ease some bowel symptoms.
  • Milk - as drinks or on cereal - is the source most likely to be giving the highest lactose load. Use soya-based or rice-based milk on cereal.
  • Calcium intake can be maintained by taking yoghurt OR by using soy milk or rice milk enriched with calcium (So Good).
  • Some UHT milks have the lactose levels reduced.
  • Lactose-free ice-cream is also available.