Knowing which foods to eat, and which ones to avoid, is powerful information when it comes to spelling relief from irritable bowel syndrome (IBS). While foods don't cause IBS, many ingredients can trigger or worsen symptoms. Finding the right diet for IBS isn't easy – figuring out which foods cause digestive distress is a highly individual, and often time-consuming, process.

It's estimated that five million Canadians live with IBS, a disorder that affects many more women than men. The main symptoms include recurrent abdominal pain and irregular bowel patterns (constipation, diarrhea or both). IBS symptoms are thought to result from overly reactive and/or extra-sensitive nerves that control muscles in the bowel.

Growing evidence, however, suggests a novel diet approach that restricts certain natural sugars found in everyday foods can dramatically improve bloating, gas and abdominal pain in most IBS sufferers. According to research from the Department of Gastroenterology at Monash University in Melbourne, Australia, a group of natural sugars (carbohydrates) called FODMAPs top the list of dietary culprits. These natural sugars include fermentable, oligosaccharides, disaccharides, monosaccharides and polyols.

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The low FODMAP diet, well-accepted and practised in Australia, has only recently begun to catch on in North America.

FODMAPs are fructose (in fruit), lactose (milk), fructans (wheat, garlic, onion), galactans (beans, lentils, soybeans) and polyols (sweeteners called sorbitol, mannitol and xylitol). Foods high in FODMAPs include barley, yogurt, apples, apricots, blackberries, pears, artichokes, cauliflower, mushrooms, pistachio nuts, cashews, honey and agave nectar. And more.

Foods naturally low in carbohydrates, such as meat, poultry, fish, eggs and fats and oils, are low in FODMAPs.

FODMAP carbohydrates are poorly absorbed in the small intestine and, as a result, make their way to the large intestine where they draw in excess water and are fermented by gut bacteria. It's thought that in people with IBS the gut is unusually sensitive to FODMAPs resulting in bloating, flatulence, abdominal pain and, in some cases, diarrhea and/or constipation.

Studies have shown that consuming FODMAPs worsens symptoms in most people with IBS and restricting their intake does a better job at easing symptoms than standard diet advice for IBS. It may sound like a difficult diet to follow, but a surprisingly high number of participants adhere to their diets (likely because they feel better).

The low-FODMAP diet takes commitment. It involves eliminating high-FODMAP foods for six to eight weeks. If these foods trigger symptoms, noticeable improvement can occur in just a few days. After the elimination period, high-FODMAP foods are slowly added back in one at a time, in correct portions, to determine which ones are well-tolerated. The goal: to find as varied a diet as possible that keeps IBS symptoms at bay.

The diet requires know-how, too. It's important to replace restricted high-FODMAP foods with those low in FODMAPs that provide missing nutrients. A dietitian knowledgeable in this specific meal planning – and the strategic reintroduction of high-FODMAP foods – can help ensure you follow a nutritionally balanced diet.

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There's also an app to help you follow a low-FODMAP diet. Developed by gastroenterologists at Monash University, the app uses a traffic-light system to identify foods by FODMAP content, as well as offer recipes and meal ideas.

This diet doesn't work for everyone – there's no one-size-fits-all IBS diet. People who have diarrhea-predominant IBS usually find relief by avoiding fatty foods (e.g. fatty meats, fried foods, cream sauces, ice cream) and other triggers such as spicy foods, coffee and alcoholic beverages.

Drinking more water and consuming a good source of insoluble fibre each day (e.g. wheat bran, 100-per-cent bran cereal) can help treat and prevent constipation and its associated bloating. Probiotics may also help relieve some IBS symptoms, especially abdominal pain and bloating. Sometimes managing IBS simply comes down to eating at regular intervals during the day (e.g. not skipping meals), preventing overeating and learning to eat slowly and mindfully.

If you are experiencing symptoms you think might be related to IBS, consult your doctor before making any dietary changes, especially unnecessary ones. It's important to rule out any other conditions that could be causing your symptoms.

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Finding FODMAPs in foods

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High FODMAPs

Meat and alternatives

Beans (e.g. chickpeas, kidney beans, lentils), soybeans

Dairy products

Milk, yogurt, ice cream, cottage cheese, ricotta cheese, sour cream

Grains

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Wheat, rye, barley, spelt, kamut, inulin (a fibre added to many foods)

Fruits

Apples, apricots, blackberries, cherries, mango, nectarine, pears, peaches, prunes, watermelon, dried fruit

Vegetables

Artichokes, asparagus, cauliflower, garlic, mushrooms, leeks, onions, snow peas

Other

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Pistachios, cashews, honey, agave nectar, sorbitol/mannitol/xylitol

Low FODMAPs

Meat and alternatives

Poultry, fish, eggs, tofu

Dairy products

Lactose-free milk and yogurt, mozzarella, Swiss cheese, Parmesan

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Grains

Gluten-free breads and cereals, corn, rice, quinoa, oats, potato

Fruits

Bananas, blueberries, cantaloupe, grapes, honeydew, kiwi, lemon, lime, oranges, papaya, pineapple, raspberries, strawberries

Vegetables

Arugula, bok choy, bell peppers, carrots, cabbage, cucumbers, eggplant, kale, lettuce, snap peas, green beans, spinach, squash, turnip, tomatoes, zucchini

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto. She is a regular contributor to CTV News Channel; lesliebeck.com.