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what causes IBS

A question that leaves many people with gut symptoms confused and distressed – What causes IBS?

Irritable Bowel Syndrome (IBS) is a disorder that affects the nerves and muscles of the bowel. It’s the least understood, but most common gastrointestinal disorder – affecting one in five Australians. IBS isn’t a disease itself, but a label given to symptoms that are not related to other conditions like coeliac disease, Inflammatory Bowel Disease etc. Therefore it’s very important to speak with your GP about your symptoms as soon as possible to rule out more serious gut conditions.

Symptoms can vary in severity and come and go, lasting for hours, days, weeks or months. For most people, it’s a chronic condition, while for others it can improve and even disappear completely. Some of the most common IBS symptoms include:
• Abdominal pain or cramping – often relieved by passing wind or bowel motion
• Altered bowel motions such as constipation or diarrhoea (or alternating between both)
• A feeling of incomplete emptying of the bowel or sudden urgency
• Mucus in the bowel motion
• A feeling of fullness, or bloating of the abdomen (due to wind or increased water volume drawn into the gut buy certain sugars and fibres)

What causes IBS?

IBS can occur at any age. For many people with this condition, the bowel appears to be over-sensitive. Unfortunately the cause isn’t always known, but a variety of factors can play a role:
• Foods: The role of food intolerance in IBS isn’t clearly understood, but many people have symptoms after eating certain foods. For some people too much fibre, fat or spices for example can be the culprit, but for others it can be trickier to identify. Our best option for testing more sensitive people is through the process of dietary elimination and then food challenges. Depending on symptoms, the Low FODMAPs diet or RPAH Elimination diet have been helpful for many people. See below for more details.
• Enzyme deficiencies: Some people are born with, or develop with age, insufficient enzymes to digest, absorb or deal with some foods. For example, a deficiency of the enzyme lactase results in lactose intolerance. Some people also benefit from supplementing the enzymes needed for fat, protein and carbohydrate breakdown.
• Stress: Most people with IBS find that their symptoms worsen or are more frequent at times of increased anxiety or stress. Such strong emotions can affect the nerves in the bowel for susceptible people. Chronic stress can also divert blood supply away from the digestive system, resulting in less effective function.
• Hormones: Because women are twice as likely to have IBS, researchers believe that hormonal changes play a role in this condition. Many women find that signs and symptoms are worse during or around their menstrual periods.
• Medications: Some medications (e.g. antibiotic, antacids, painkillers) and supplements (e.g. iron) can cause gut irritations and lead to constipation or diarrhoea.
• Other factors: For example, an acute episode of gastroenteritis or food poisoning; bacterial infections or parasites; dysbiosis (an altered balance of good and bad microbes in the large bowel) or too many bacteria in the small intestines (bacterial overgrowth e.g. SIBO), can cause the gut to become more sensitive and trigger IBS.

How to manage your symptoms:

Your dietitian’s first priority will be to get you feeling better. Most people can improve their IBS symptoms with changes to diet, improving stress management and prescribed medications (if required). Some of the dietary changes that can help improve symptoms include reducing high fat and/or sugar foods, spicy foods, foods high in insoluble fibres, gluten, dairy proteins, coffee and alcohol, and reducing meal sizes. Many people find relief in symptoms from following a low FODMAPs diet. FODMAPS (Fermentable Oligo-saccharides, Di-saccharides, Mono-saccharides and Polyols) are sugars that are poorly absorbed in the gut. They travel to the large bowel where they can be food for gut bacteria, or draw water into the gut through osmosis. For people with gut sensitivity, this can cause symptoms.
The low FODMAPs diet is a short-term (3-4 weeks) investigative diet, followed by a systematic food challenge process, to identify problematic foods. It is important that you seek guidance from your dietitian through this process to ensure you are following the most appropriate guidelines and have the diet tailored to your needs. If your symptoms don’t subside through the dietary changes suggested above, other issues including poor digestion (mechanical and / or chemical factors) or food chemical intolerance (naturally occurring and additives) may be considered, depending on symptoms. The gold standard to investigate food chemical intolerance in Australia is following the RPAH Elimination diet.
Once symptoms have subsided or significantly improved, a number of things can be considered to treat or manage IBS. For example, if dysbiosis is suspected, a number of specific probiotic supplements can be helpful to reduce inflammation in the gut, reduce unhelpful bacteria and increase bacteria helpful for a healthy gut. If digestive support is needed, digestive enzyme supplements may be useful. Gut calming agents like Iberogast can also be useful to soothe the gut and improve motility (movement through the bowel).
Getting advice for an appropriate short-term and long-term diet from a dietitian experienced in gastrointestinal conditions, IBS and investigative diets, is very important to ensure you are getting the right nutrients for gut repair, general health and to feed the healthy bacteria you are supplying through supplementation.

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Amanda Moon

Author Amanda Moon

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