What is a Low FODMAP Diet?

by Carmen Roberts, M.S., R.D., L.D.N. Health Professional, Medical Reviewer

The low FODMAP diet is used to help alleviate symptoms of irritable bowel syndrome (IBS). It can also help with symptoms of Crohn’s disease, ulcerative colitis, and celiac disease. It is not a cure for these diseases, but it may help to prevent bloating, cramping, diarrhea, flatulence, and other symptoms that are common for people who suffer from these conditions.

The term “FODMAP” is an acronym for the poorly absorbed short-chain carbohydrates that feed on naturally-occurring bacteria found primarily in the large bowel: fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.

For people living with IBS, consumption of these sugars and sugar alcohols can cause digestive discomfort. The intestinal bacteria found in the large bowel feed on these indigestible sugars, leading to negative gastrointestinal symptoms. The premise of this diet is that through avoidance of FODMAPs, symptoms of digestive discomfort may be eliminated.

Many carbohydrates in food are poorly digested and not absorbed by the small bowel. One example of this is dietary fiber. Some oligosaccharides and simple sugars cannot be absorbed but can be broken down by intestinal bacteria, producing gas. To reduce the amount of gas produced, a person following a low FODMAP diet should eat a limited amount of carbohydrates, except those that are readily digested (such as sucrose and glucose).

The approach to this diet is to eliminate all foods containing high amounts of FODMAPs for eight weeks. After eight weeks, you slowly reintroduce FODMAPs into your diet, one food group at a time. Using this technique, you may be able to find out which of the FODMAPs are contributing to increased gas production in the bowel. For many people, simple avoidance of one or two of these carbohydrates that are causing most of the gas production causes a dramatic decrease in their IBS symptoms.

What are the foods to avoid on a low FODMAP diet?

The list of foods to be avoided is extensive, and includes (but is not limited to) the following:

  • Oligosaccharides (fructans and galacto-oligosaccharides): wheat, garlic, onion, beans, lentils, artichokes, Brussels sprouts, and soy-based products

  • Disaccharides (lactose): all milk-containing products, including cow’s milk, yogurt, and cheese

  • Monosaccharides (fructose): many fruits (including watermelon, mangoes, apples, and pears), honey, agave, and high-fructose corn syrup

  • Polyols (sugar alcohols): sorbitol, mannitol, mannitol, xylitol, polydextrose, and isomalt

What is OK to eat?

There are many fruits and vegetables that are not on this list that are fine to eat during the elimination period. These include grapes, oranges, strawberries, carrots, kale, lettuce, and squash, to name a few. To ensure you are getting adequate calcium, consider adding dairy alternatives such as almond or coconut milk or yogurt to your diet.

How effective is the FODMAP diet?

Multiple research studies have concluded that the low FODMAP diet can be an effective dietary intervention for treatment of IBS. However, researchers continue to study the long-term effects of following a low FODMAP diet.

Bottom line: Is the FODMAP diet for me?

If you suffer from IBS, the low FODMAP diet may be a reasonable, safe treatment option. However, it must be initiated under medical supervision to properly evaluate its effectiveness at alleviating your chronic symptoms. A registered dietitian and/or a gastroenterologist skilled in the execution of the low FODMAP diet can assist you in implementing the diet while ensuring that your diet remains nutritionally balanced during the elimination period.

Carmen Roberts, M.S., R.D., L.D.N.
Meet Our Writer
Carmen Roberts, M.S., R.D., L.D.N.

Carmen is a Registered Dietitian. In addition to writing for HealthCentral, she has spent her career working at Johns Hopkins and is also an adjunct faculty instructor for Excelsior College. Carmen has over 20 years of experience in nutritional counseling, education, writing, and program management and is a certified specialist in adult weight management. She enjoys educating her students and clients about how nutrition affects the body and its role in overall health and wellness.