Because irritable bowel syndrome has such a wide range of symptoms, the diagnosis has become something of a ‘catch-all’. Before you start any medication regimen it’s therefore essential to rule out other conditions that may be causing your digestive problems.

    Irritable bowel syndrome (IBS) is one the most commonly diagnosed digestive disorders. If you haven’t yet been told you have it, chances are that you know someone who has. But is it really possible that so many of us suffer from this condition, or has the term IBS become synonymous with ‘I don’t really know what’s wrong with you, so let’s call it IBS?’

    When a patient presents with IBS-type symptoms, how often does the doctor do investigations for disorders such as increased gut fermentation, histamine intolerance, small-intestinal bacterial overgrowth (SIBO), post-food poisoning syndrome or hidden allergies, intolerances and other immune responses? Very rarely!

    This is because the many forms and presentations of IBS can make the diagnosis a particularly challenging one, and its functional nature can make a satisfactory treatment regimen difficult. More often than not patients are sent home with antispasmodic medication or tricyclic antidepressants, or told to eat more fibre, or take more probiotics. Success rates of both conventional and complementary medicines are therefore historically quite low.

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    The gut contains the greatest concentration of immune tissue in the body. These immune cells are intertwined with the greatest concentration of nerves outside the central nervous system. Both immune cells and nerves are continually communicating with the mucosal epithelia (the cells that line the gastro-intestinal tract). These interactions control both the physiological and patho-physiological aspects of gut function.

    Communication between the gut nervous system and the central nervous system is common, and is known as the gut-brain axis. Disturbances in either have effects that resound throughout the body. The same neurotransmitters that influence the gastro-intestinal tract also influence endocrine, immune, behavioural and emotional function. Stress (either psychological or physiological) may therefore be an important factor in gastro-intestinal health.


    Faulty digestion or absorption of carbohydrates and sugars by the small intestine allows increased amounts of these foods to reach the colon, where greater amounts of gas are produced. This increased gut fermentation is characterised by bloating, constipation, diarrhoea, fatigue and gas – symptoms often associated with IBS.

    The most common example of malabsorption leading to increased production of gas is lactose (milk) intolerance. Lactose intolerance is caused by a genetic lack of the enzyme in the lining of the small intestine that digests lactose, the sugar in milk.

    Other causes of malabsorption that may lead to excessive production of gas and be mistaken for IBS include: malabsorption of sugars such as sucrose, sorbitol, or fructose, inadequate amounts of pancreatic enzymes (necessary for digesting sugars and carbohydrates in the small intestine) diseases of the lining of the small intestine (e.g. coeliac disease) that reduce enzymes in the lining necessary for breakdown and absorption of sugars and carbohydrates.

    Malabsorption is often characterised by an overgrowth of pathogenic bacteria. These bacteria damage the intestinal brush borders, resulting in increased intestinal permeability that may increase the incidence of allergies, intolerances, emotional disturbances and vitamin and mineral deficiencies.


    There is increasing evidence that histamine intolerance is a major cause of food hypersensitivity, facial flushing and IBS-related symptoms. Studies have shown that histamine-intolerant individuals may have a deficiency of certain enzymes in the small-intestinal mucosa. This type of deficiency results in decreased breakdown and increased absorption of histamine in the gastro-intestinal tract.¹

    Symptoms associated with histamine intolerance vary greatly but include:

    • hay fever, flushing, wheezing, urticaria, asthma
    • bloating, diarrhoea, abdominal migraines (an increasingly recognised condition involving abdominal distress accompanied by nausea and often repeated vomiting), nausea, hypersensitivity to many foods
    • low blood pressure, migraines, tension headaches, anxiety, depression and panic attacks.

    Histamine intolerance testing is not currently widely available in South Africa, so excluding foods high in histamines for a few weeks and then reintroducing them can be quite effective in establishing a connection. Additionally, taking an enzyme formula containing diamine oxidase (DAO) can be helpful.

    High-histamine foods include all minced meat, sausages, salami, all tinned and smoked fish, all ripe cheeses, yeast, sauerkraut, avocado and tomatoes. Some foods that should be excluded because they liberate histamines include kiwi fruit, papaya, grapefruit and pineapple.

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    Post-infectious IBS (PI-IBS) is a subgroup of IBS that is diarrhoea-predominant. Having an episode of bacterial gastroenteritis may increase the risk of developing IBS symptoms within the same year. Gastroenteritis is a pathological disturbance of the gastro-intestinal tract often (but not always) caused by bacteria or viruses and more rarely by fungi or parasites. It is associated with inflammation.

    Post-food poisoning syndrome (PFPS) is a new field of research. It shares many of the same symptoms as PI-IBS and is therefore easily misdiagnosed. The most commonly recognised food-borne infections are those caused by the bacteria Campylobacter, Salmonella and E. coli. Food poisoning will always cause an imbalance in the normal gut flora (dysbiosis), with those in recovery suffering from symptoms for quite a while after the poisoning


    The small intestine is the section of the gastro-intestinal tract that connects the stomach with the colon. Its main purpose is to digest food and absorb it into the body.

    The entire gastro-intestinal tract, including the small intestine, normally contains bacteria. The number of bacteria is greatest in the colon and much lower in the small intestine. Moreover, the types of bacteria in the small intestine are different to the types of bacteria in the colon.

    SIBO is a condition in which abnormally high numbers of bacteria are present in the small intestine, and in type resemble the colon bacteria rather than the bacteria that normally inhabit the small intestine.

    This imbalance of bacteria may result in excess gas, abdominal bloating, diarrhoea and abdominal pain, symptoms not dissimilar to those often diagnosed as IBS.


    The gastro-intestinal tract is a continuous muscular tube through which digesting food is transported. The muscular activity that sweeps through the small intestine is important not only for the digestion of food, but also because it sweeps bacteria out of the small intestine and keeps down the numbers of bacteria there. Any condition that interferes with muscular activity in the small intestine results in bacterial over- growth. Lack of muscular activity may even allow bacteria to spread backwards from the colon and into the small intestine.


    • Post-food poisoning syndrome.
    • Long-term viral infections.
    • Neurological and muscular diseases that alter the normal activity of the intestinal muscles. For example, both diabetes mellitus and scleroderma may result in abnormal muscular activity in the small intestine, allowing SIBO to develop.
    • Partial or intermittent obstruction of the small intestine from adhesions (scarring) from previous surgery or Crohn’s disease.
    • Diverticuli (out-pouchings) of the small intestine that allow bacteria to multiply inside them.

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    Before accepting a diagnosis of IBS, it is important to explore all other possibilities.

    Some tests to consider:

    • Comprehensive Digestive Stool Analysis may help identify bacterial imbalances in the gut as well as confirm the existence of pathogenic microbes.
    • Urine Organic Acids measures the by- products of microbial metabolism, and is particularly useful in detecting the presence of pathogenic microbial over- growth. Urine is an important medium for testing microbiology in the gut. Urine contains unique products of microbial metabolism which are used to measure small bowel yeast and bacterial overgrowth.
    • Intestinal Permeability and Absorption is a test designed to determine the health and efficiency of multiple gastro-intestinal functions. Of specific interest are increased intestinal permeability (or ‘leaky gut’), intestinal damage, gut function, lactose intolerance, sucrose intolerance, and the health of the intestinal villa.


    Just as there is no one cause of IBS-type symptoms, there is no one diet that works across the board. Dietary management is crucial but usually requires progressive changes and modifications. Some diets to consider are:

    • Exclusion and Reintroduction Diets can be very effective in pinpointing and ad- dressing food sensitivities and intolerances that may be contributing to the symptoms.
    • Specific Carbohydrate Diet (SCD). Eliminates all disaccharides and all polysaccharides. Only monosaccharides such as fruits, sugar and most non-starchy vegetables are allowed alongside protein and fats. The diet has six stages.
    • Low FODMAPs diet. FODMAPs (stands for Fermentable Oligo-saccharides, Di-saccharides, Mono saccharides and Polyols) can be poorly absorbed in the small intestine. Malabsorbed carbohydrates are fermented by gut bacteria to produce gas. This diet excludes high FODMAPs foods such as wheat, legumes, milk, apples, pears, sweet corn, a number of vegetables and some nuts.
    • Gluten exclusion. More often than not, gluten sensitivity is implicated in gastrointestinal disorders. A gluten exclusion diet means avoiding all gluten-containing foods for a minimum of three months. This is because it can take a minimum of three months (and in some cases up to six months) for the inflammation associated with gluten to subside.


    It is very easy to misdiagnose IBS owing to its wide range of symptoms. It is therefore essential to get a clear diagnosis and rule out other possible causes before starting any medication regimen. Paramount to successful treatment is ensuring that all practitioners work together, including laboratory experts, the gastroenterologist, and the nutritional therapist. The route to resolution can be a bumpy one.

    Editors' Note: For more articles on IBS read Gut Instincts guiding you to health, IBS – The Internal Struggle and FODMAPS and dietary management of IBS 


    1. Maintz L. and Novak N. Histamine and histamine intolerance. Am J Clin Nutr 2007; (85): 1185-96.
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