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IBS: A low-FODMAP diet can help

April 09, 2024 | Valerie Elwell
A young woman at work is hunched over in pain resting her head on her laptop.

IBS symptoms can take a heavy toll, not just on a person's physical and emotional well-being but also on their social and professional life.

Irritable bowel syndrome (IBS) is a chronic, often debilitating gastrointestinal disease that affects as many as 45 million Americans.

There is as yet no cure, but diet is the first line of defense. Doctors are increasingly recommending the low-FODMAP diet to target some types of carbohydrates that are not easily digested.

It is considered a front-line therapy for IBS in many parts of the world.

"The diet was designed to help people with IBS determine which foods are problematic and which foods reduce their symptoms through a process of elimination," says gastroenterologist Dr. Christina Ling, who treats many IBS patients at the UCI Health Inflammatory Bowel Disease Program.

National Institutes of Health study found that 86% of IBS patients who followed a low-FODMAP diet reported substantial improvement in symptoms such as abdominal pain, cramps, bloating, constipation and diarrhea.

What is FODMAP?

FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides and polyols — short-chain carbohydrates (sugars) that are pervasive in modern diets.

Common FODMAPs include:

  • Fructose — a simple sugar found in many fruits and vegetables; also makes up the structure of table sugar and most added sugars
  • Lactose — a carbohydrate found in dairy products
  • Fructans — a polymer of fructose molecules found in many grains like wheat, spelt, rye and barley
  • Galactans — a polymer of galactose found in legumes
  • Polyols — sugar alcohols like xylitol, sorbitol, maltitol and mannitol that are often used in sweeteners and also found in some fruits and vegetables

The low-FODMAP diet

In the early 2000s, researchers at Monash University in Australia discovered that the small intestine does not absorb these sugars very well and can increase the amount of fluid and gas in the bowel. This leads to bloating and a change in the speed of digestion in sensitive individuals, resulting in cramping, pain, constipation and/or diarrhea.

They developed the low-FODMAP diet, which is designed to identify IBS triggers in three steps. Here's how it works:

  • Elimination — You eliminate all FODMAP carbs for several weeks. Symptoms may improve immediately or over the course of several weeks.
  • Reintroduction — You reintroduce foods high in FODMAP, one at a time to identify the ones you can tolerate and in what amount.
  • Personalization — You modify your diet, adjusting the type and amounts of FODMAPs based on the findings in step 2.

“Because the elimination stage of the diet can be challenging, it’s essential to work with a doctor or dietitian who can ensure you’re following the diet correctly while still meeting your nutritional needs,” says Ling, an assistant professor in the Division of Gastroenterology & Hepatology in the Department of Medicine at UCI School of Medicine. "That is crucial to success.”

Once your food sensitivities have been identified, a dietitian can help you develop a well-balanced, gut-friendly diet that will keep your IBS symptoms at bay.

What to eat, what to avoid

Foods that trigger IBS symptoms vary from person to person.

These high-FODMAP foods are known to cause gut irritation in some people:

  • Dairy: Cow’s milk, ice cream, most yogurts, soft and fresh cheeses (cottage cheese, ricotta, etc.), pudding, custards, sour cream, whey protein supplements
  • Fruit: Apples, applesauce, apricots, blackberries, blueberries, boysenberries, cherries, dates, figs, grapes, nectarines, peaches, pears, plums, raspberries, watermelon
  • Sweeteners: Agave nectar, fructose, high fructose corn syrup, honey, isomalt, malt extract, maltitol, mannitol, molasses, sorbitol, xylitol
  • Vegetables: Artichokes, asparagus, beetroot, broccoli, Brussels sprouts, butternut squash, cabbage, cauliflower, fennel, garlic, karela, leeks, mushrooms, okra, onions, peas, shallots
  • Legumes: Beans, baked beans, black-eyed peas, broad beans, chickpeas, fava beans, lentils, pinto beans, red kidney beans, soybeans, split peas
  • Wheat: Biscuits, bread, most breakfast cereals, crackers, pancakes, pasta, tortillas, waffles
  • Other grains: Amaranth, barley, rye
  • Beverages: Coconut water, fruit juices, oat milk, soy milk, tea (chai, chamomile, fennel), kombucha, soft drinks sweetened with high-fructose corn syrup, fortified wines and rum

These low-FODMAP foods are easier to digest:

  • Dairy: Almond milk, lactose-free milk, rice milk, coconut milk, lactose-free yogurt, hard cheeses
  • Fruit: Bananas, blueberries, cantaloupe, grapefruit, honeydew, kiwi, lemon, lime, oranges, strawberries
  • Vegetables: Bamboo shoots, bean sprouts, bok choy, carrots, chives, cucumbers, eggplant, ginger, lettuce, parsnips, potatoes, spring onions, turnips
  • Protein: Beef, pork, chicken, fish, eggs, tofu
  • Nuts/seeds: Almonds, peanuts, walnuts, macadamia nuts and pine nuts
  • Grains: Oats, oat bran, rice bran, gluten-free pasta, quinoa, white rice, corn flour

Keep in mind that many high-FODMAP foods are very nutritious and some provide healthy fibers that support gut-friendly bacteria, says Ling. But for people with a FODMAP intolerance, they can wreak havoc on the digestive tract and should be avoided or eaten in small quantities.

Why consider a low-FODMAP diet?

If you frequently experience symptoms of IBS, Ling recommends seeing a gastroenterologist for further evaluation as other conditions can also cause the same symptoms.

If IBS is diagnosed, testing your sensitivity to FODMAPs can then be explored with your doctor.

Eating a low-FODMAP diet may not eliminate all symptoms of IBS, says Ling. But chances are high that it may lead to significant improvements in digestive health and overall quality of life.

Learn more or schedule a visit with a UCI Health gastroenterologist who treats IBS and IBD ›

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