The Role of the Low FODMAP Diet in IBS Symptom Management

Generally speaking, we naturally lack the enzymes required to digest certain FODMAPs. However, for those with IBS, a phenomenon called 'visceral hypersensitivity’ is the reason why FODMAPS can cause such disturbing symptoms.

Breaking down FODMAPs

Fermentation occurs in the gut when bacteria present in the large intestine consumes the short-chain carbohydrates.

Oligosaccharides are mainly fructans and GOS, which are malabsorbed in the gut due to our lack of fructan and GOS-degrading enzymes. These are highly fermentable by gut bacteria, causing gas production, abdominal pain, and bloating in IBS.

Disaccharides refers to lactose, a poorly digested double-sugar present in those lacking the lactose-degrading enzyme known as lactase. This is common in people of Asian and Mediterranean backgrounds, and also in diseases causing intestinal inflammation (such as Crohn's disease), with prevalence increasing with age.

Most people are able to digest lactose and don't need to follow the lactose component of the low FODMAP diet. If you're unsure as to whether or not this applies to you, chat to your doctor or an accredited/registered dietitian.

Monosaccharides represent fructose, the smallest FODMAP sugar. When fructose is present in greater quantities than glucose in your gut, this osmotic imbalance enables ready-attraction of water into your intestine, causing pain, bloating, large amounts of diarrhea, and altered transit through the gut.

‍Polyols commonly include mannitol, maltitol, xylitol, and sorbitol, and are often found in sugar-free chewing gum, sugar-free products, and in some fruits and vegetables. These molecules are ‘sugar alcohols’, and are similar to fructose in that these are poorly absorbed in the gut and may cause the same effects as excess fructose.

Here are some foods high in FODMAPs:
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• ‍Polyols: Avocado, button mushrooms, green apples, apricot, blackberries.

• ‍Fructose: Watermelon, mango, asparagus, peaches, plums, nectarines, honey.

• ‍Fructans: Onion, garlic, ripe banana, figs, multigrain and rye bread, wheat-based gnocchi.

• ‍Lactose: Cow's milk, natural Greek yoghurt, vanilla ice cream (two scoops).

• ‍GOS: Cashews, pistachios, soy protein, silken tofu, red kidney beans, pinto beans, falafel.

Here are some foods low in FODMAPs:

• ‍Vegetables: Cucumber, iceberg lettuce, oyster mushrooms, olives, spring onion (green tops only), unpeeled potato, jap pumpkin, radish.

• ‍Fruits: Navel oranges, starfruit, raspberries (under 30), two small green kiwis, six grapes, clementine, one medium-firm banana.

• ‍Grains: Unprocessed bran, gluten-free bread, rolled oats, spelt sourdough, one slice white bread, gluten-free flour, gluten-free pasta, quinoa, brown and white rice.

• ‍Lean meat/alternatives: Tempeh, one cup firm tofu, egg replacer, 1/4 cup rinsed canned chickpeas and beans, brazil nuts, chestnuts, macadamia, peanuts, pine nuts, chia seeds, hemp seeds, sesame seeds.

• ‍Dairy: Lactose-free milk, butter, cheddar, feta, parmesan, nut milk, lactose-free yoghurt

Good to know: rinsing legumes prior to eating helps to wash out the FODMAPs as they are water soluble.

Download the Monash University FODMAP Diet app for more information about foods high and low in FODMAPs. You'll learn which foods have been tested by the Monash FODMAP team and categorised via a traffic light system for FODMAP safety.

Low FODMAPs for IBS symptom management

Up to 15% of the Western population experience IBS, and you're likely to make at least five annual visits to the doctor. A diet high in FODMAPs has been found to increase symptoms of excessive flatulence, abdominal cramping, constipation, bloating, and diarrhea in individuals diagnosed with IBS.

Current research shows that the low FODMAP diet is effective in relieving IBS symptoms in up to 86% of patients.

Fun fact: hypnotherapy equaled the low FODMAP diet in symptom relief, and you can try both at the same time.

Note that the common symptoms of IBS (abdominal pain, bloating, and alternating bowel habits) can overlap with those typical of Coeliac disease, colon cancer, Inflammatory Bowel Disease (IBD), endometriosis, and Polycystic Ovary Syndrome (PCOS) among others. This means it's imperative that you get a clear and accurate diagnosis to make sure you receive appropriate treatments and manage your IBS with the right tools.