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Irritable Bowel Syndrome [IBS] & FODMAPs

Avoid these for symptomatic relief

What exactly are FODMAPs?

FODMAPs is an acronym that stands for the following:

  • Fermentable
  • Oligo-saccharides
  • Di-saccharides
  • Mono-saccharides,
  • Polyols

These are short-chain carbohydrates and sugar alcohols [polyols] that are widespread in the diet. There is an increasing intake of polyols in the diets of many people as these are used as artificial sweeteners in many products. Many confectionary products in particular sugar-free chewing gums and sugar-free lollies have sugar alcohols such as sorbitol, xylitol, isomalt and maltitol that are used in place of sugar as artificial sweeteners.

Fructose is found in high concentration in certain fruits, dried fruits and fruit juices and lactose is found in many dairy products. In the wrong individual who suffers from a functional bowel disorder such as irritable bowel syndrome [IBS], these short-chain carbohydrates can produce significant and debilitating symptoms.

Individuals with Ulcerative Colitis or Crohn's Disease [Inflammatory Bowel Disease or IBD]

  • It is important to note that functional bowel disorders are 2 - 3 times more common in individuals suffering from inflammatory bowel disorders such as Crohn's Disease and Ulcerative Colitis or those with an ileal pouch38.
  • These individuals diagnosed with inflammatory bowel disease may benefit greatly from a low FODMAP diet.

Why are FODMAPs important in IBS and how do they cause symptoms?

These short-chain carbohydrates can cause symptoms because they are:

  1. Osmotically active: high concentrations of FODMAPs in the bowel interior can cause water to be drawn from the bowel lining into the bowel canal causing diarrhoea.
  2. Fermentable: bowel bacteria [bowel flora] can ferment or breakdown the FODMAPs resulting in the production of copious amounts of hydrogen, carbon dioxide and methane leading to bloating, abdominal distention, increased bowel sounds and abdominal pain due to stretching of the bowel walls as a consequence of trapped gas.
  3. 'Fast-Food' for Bowel Bacteria resulting in  Small Bowel Bacterial Overgrowth: This bacterial overgrowth can produce gas in the small bowel which in contrast to the large bowel is a confined space, causing pain, bloating, foul smelling diarrhoea, possibly halitosis and a coated tongue and producing a general feeling of being unwell. Such a cesspool of pathogenic bacteria may well and truly make you feel quite sick and lethargic. You may need antibiotics to get your small bowel bacterial flora back to normal - see below.

Irritable Bowel Syndrome [IBS], Inflammatory Bowel Disease [IBD]

  • A low FODMAP diet will be of benefit not only for those suffering from irritable bowel syndrome (IBS) but also for those individuals suffering from Crohn's Disease and Ulcerative Colitis34,35.

Fermentation of FODMAPs

  • Although osmosis [the drawing of water from the bowel wall into the bowel lumen] can cause diarrhoea, it is the fermentation of the FODMAPs that can cause all the misery in an individual sensitive to the gas produced by fermentation.

Small Bowel Bacterial Overgrowth Syndrome

  • Bacteria in the small bowel thrive on these FODMAPs which are known as 'fast-food' for these organisms. An abnormal growth of bacteria occurs in the small bowel as a result causing not only discomfort but potential harm to the individual due to toxic elements being either produced or released as a result of bacterial action.
  • For individuals who wonder why they alternate between diarrhoea and either normal bowel motions or constipation, this FODMAP story may well provide the answer for many individuals suffering from IBS.
  • The simple reason that individuals alternate between diarrhoea, normal stools and constipation, is that your intake of FODMAPs may be quite variable during the course of a day or a week. The higher the FODMAP load you consume in your diet, the higher the probability that you will be suffering from a small bowel overgrowth syndrome. You may just need to reach a certain threshold of FODMAP intake to trigger off small bowel overgrowth syndrome and this threshold will vary between individuals.

The use of antibiotics may be needed

  • Antibiotics may be needed in someone who is suffering from persistent diarrhoea and this may normalize fructose malabsorption. Stool cultures should be done first to exclude other parasitic or pathogenic infections before commencing antibiotic treatment. One study stated:

    "Eradication of small intestinal bacterial overgrowth normalizes sugar breath tests in the majority of patients36."

  • So you may need a course of antibiotics to eradicate the abnormal bacteria in the small intestine and perhaps undertake a course of probiotics to help re-establish a normal colony of small bowel flora. One article found amoxycillin-clavulanic acid to be very effective in treating small bowel bacterial overgrowth: 

    "Bacterial sensitivities from duodenal intubations with nonidiopathic bacterial overgrowth syndrome support the use of amoxicillin-clavulanate. Amoxicillin-clavulanate appears to be 75% effective in patients with diabetes.39"
  • Metronidazole [Flagyl®] may need to be added to the amoxicillin-clavulanic acid [Augmentin®] for anaerobic bacteria and yeast overgrowth may also need to be treated with nystatin. Discuss this with your local doctor or perhaps a Gastroenterologist.
  • Rifaximin is a semi-synthetic, non-systemic antibiotic - in other words it is minimally absorbed into the body from the gastrointestinal tract. This antibiotic has been used very successfully in traveller's diarrhoea caused by E'coli infections. One study found sustained improvements in IBS concluding:
    " Rifaximin improves IBS symptoms for up to 10 weeks after the discontinuation of therapy37."
  • Staying on a limited FODMAP intake diet will help to decrease your risk of small bowel bacterial overgrowth syndrome.

Why do a breath test?

Hydrogen-Methane breath tests are done to exclude:

  1. Lactose Intolerance [dose of lactose]
  2. Fructose Intolerance [dose of fructose]
  3. Small Bowel Overgrowth Syndrome [dose of Lactulose]
  • This is a simple test that is done over a 2 - 3 hour period in a specialized collection unit where your breath is analyzed for hydrogen and methane.
  • Elevations in these gases are used as evidence of lactose or fructose malabsorption. 
  • The advantage of this testing is to see whether an individual actually needs to restrict dairy [lactose] or fructose containing foods.
  • The limitation of this test is that only fructose and lactose can be analyzed in this way. Other FODMAPs will still need to be restricted.

Microbial Ecology Profile: DNA Analysis

  • The type and number of bowel organisms can be analyzed by DNA assessment of your stool sample.
  • Gone are the days of trying to grow organisms on or in a medium of some kind and incubating this medium followed by complex analysis to identify the organism present. This laborious method is now being replaced by DNA studies of samples that can identify organisms present - ie a genetic fingerprint of the organisms present in a particular sample.
  • Bacteria: This study can provide you with an indication of the predominant bacteria in the stool in terms of Obligate anaerobes [Bacteroides, Clostridia, Fusobacteria etc.], Facultative anaerobes [Lactobacillus sp. and Bifidobacter sp.], Obligate aerobes such as E'coli or Pathogenic bacteria such as Helicobacter pylori, E.H.E Coli, Campylobacter and Clostridium difficile.
  • Yeast/Fungi: Yeast overgrowth can also occur in the bowel and this will also be assessed by DNA analysis
  • Parasites: Such as Cryptosporidium, Entamoeba species, Blastocystis hominis, Dientamoeba fragilis, worms etc are also looked for in the sample.
  • It is important not to assume you have IBS and that a FODMAP exclusion diet will help. You need to actively exclude other pathology.

Are other tests recommended? - The food IgG Test

  • Although controversial at the time of writing, testing for IgG antibodies to certain foods can be an important step to find out if you have specific food sensitivities. Avoiding IgG positive foods in your diet may produce symptomatic relief.
  • FODMAP restriction may not provide benefit for everyone or symptoms may improve but are still present to a significant extent. In this instance it is important to assess for food sensitivity with IgG testing. The food IgG test is not a test for food allergy which is IgE related and IgE is tested for using RAST tests.
  • Irritable Bowel Syndrome is also a diagnosis by exclusion. In other words, you need to exclude other problems that could mimic the symptoms of irritable bowel syndrome such as Coeliac Disease, Crohn's Disease and Ulcerative Colitis among others. It is thus prudent to see a Gastroenterologist to investigate your symptoms to see if it is actually due to a medical problem.

Why do some types of fibre make things worse?

  • Many soluble fibres are available in supermarkets now such as Inulin [Fibresure®] and inulin is a FODMAP.
  • Inulins are long chain polymers of fructose
  • Individuals with IBS or Crohn's or Ulcerative Colitis should avoid foods containing inulin or fibre supplements like Fibresure®
  • However, soluble fibre is recommended in irritable bowel syndrome as insoluble fibre can aggravate symptoms. Try oat bran and chia seed bran as possibilities as these fibres are soluble fibre rich and oats have the advantage of beta-glucan that can help lower cholesterol levels.

A special mention about wheat intolerance

  • Many people avoid wheat-based products because they are concerned about gluten sensitivity.
  • The NutriDesk FODMAP eBook will explain the problem with wheat and why you may need to avoid this grain if you are an IBS sufferer.

What should I avoid? - Some downloadable files help you

Link to QuickGuide Topic References

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QuickGuide Topic References


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