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A Dietitian's Guide to the Low-FODMAP Diet

Updated: Feb 7, 2022

If you've ever experienced digestive issues or follow health trends, you may have heard of the low-FODMAP diet. It can be a confusing and overwhelming diet. In this article, we'll outline what the low-FODMAP diet is, who may benefit from it, and how to do it.

FODMAP is an acronym that stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are short chain carbohydrates that contain fibers which humans lack the enzymes to digest. Our gut bacteria ferment these fibers, and produce short-chain fatty acids (SCFA) which have many health benefits. However, in those who have an overgrowth of bacteria or struggle with digestive distress, this may lead to excessive fermentation and can manifest in gastrointestinal symptoms.

Who should try the Low-FODMAP diet?

Indications to try the Low-FODMAP diet include: IBS, IBD, SIBO, GI symptoms related to a non-specific cause.

  1. Irritable bowel disease (IBS) is a condition in which your large intestine has abnormal contractions. Symptoms of IBS include: bloating, gas, abdominal pain, diarrhea and/or constipation. There are 3 different types of IBS: IBS-C, IBS-D, IBS-M which stand for constipation predominant, diarrhea predominant, and mixed respectively. Mixed means exactly what you’re thinking--a mix of diarrhea and constipation.

  2. Inflammatory bowel disease (IBD) is ongoing inflammation in part of the digestive tract. Crohn’s disease and ulcerative colitis are the two types of IBD. Crohn’s disease is inflammation in all four layers of the GI tract. It can affect any part of your small or large intestine but most commonly affects the end of the small intestine (ileum) and the beginning of the colon (ascending colon). The inflammation can affect the intestines in a continuous fashion or it can skip segments. Ulcerative colitis usually affects the innermost lining of the large intestine or rectum.

  3. Small intestinal bacterial overgrowth (SIBO) happens as a result of an abnormal increase in the amount of bacteria in the small intestine--particularly types that are not usually found in a certain part of the small intestine. Symptoms of SIBO may include excessive bloating, gas, constipation and/or diarrhea related to bacteria fermentation.

  4. Gastrointestinal symptoms such as bloating, gas, abdominal pain, or irregular bowel habits that have not been resolved or received a formal diagnosis.

What is the Low-FODMAP Diet?

The low-FODMAP diet is a type of short-term elimination diet. It should not be done long-term - it is meant to be a temporary therapeutic diet therapy lasting between 2-6 weeks. There are 2 main phases to the diet: the elimination phase and the reintroduction phase.

Phase 1: Elimination phase - consists of eliminating all foods that contain FODMAPs from your diet. Typically the elimination period of all these groups of food is 2-6 weeks. We typically see the most success with an elimination phase of at least 3 weeks.

Phase 2: Reintroduction phase - consists of gradually adding a FODMAP group back into your diet one at a time.

Elimination Phase

Below are examples of foods that are HIGH in FODMAPs that should be eliminated during the elimination phase:

1. Oligosaccharides

  • Sources: Wheat products, garlic, onions, shallots, cabbage, broccoli, pistachio, artichoke, chicory root, lentils, chickpeas, beans

2. Disaccharides

  • Sources: Cow’s milk, yogurt, cheese, ice cream, sour cream

3. Monosaccharides

  • Sources: Honey, mango, figs, sucrose, asparagus, agave syrup

4. Polyols

  • Sources: Sorbitol, maltitol, mannitol, xylitol (sugar alcohols)

    • Products with sugar alcohols: chewing gum, no sugar products

    • Products sugar alcohols are found naturally in include: apples, blackberries, peaches, plums, mushrooms, cauliflower, snow peas

Examples of foods you can eat during the Elimination phase

(Note: this does not include ALL foods that are allowed)

  • Fruit

    • Cantaloupe, grapes, honeydew, kiwi, oranges, pineapple, raspberries, strawberries, banana (small firm)

  • Vegetables

    • Arugula, beets, bell peppers, broccoli, carrots, eggplant, cabbage, cucumbers, tomatoes, white potatoes

  • Dairy

    • Butter, hard or aged cheeses, non-dairy milk

  • Grains

    • Corn products, GF bread (without FODMAP ingredients)

  • Protein

    • Beef, chicken, eggs, fish, lamb, pork, shellfish, tofu

  • Nuts/oils/seeds

    • Almonds, peanuts, pecans, walnuts, chia seeds, flax seeds, hemp seeds, olive oil, avocado oil

Sample day of eating during elimination phase:

Breakfast: Eggs, tomato, avocado & bean sprouts on gluten-free or sourdough bread with a slide of sliced oranges

Lunch: Chicken salad: chicken, mayo, grapes, celery mixed together. Served on gluten-free bread or lettuce wraps. Paired with bell peppers & Primal Kitchen Ranch (or another low-FODMAP friendly dressing)

Dinner: Seared/grilled salmon (olive oil, chili powder, salt, pepper), well-cooked carrots and white potatoes with parsley

Snack ideas: rice cakes + 1-2 tbsp of peanut butter/almond butter, canned tuna with mayo + cucumbers, deviled eggs + carrots, plain tortilla chips + Fody foods salsa

There are LOTS of resources available to make a low-FODMAP diet as easy as possible! I provide clients with guides that clearly outline what foods to eliminate, what types of foods contain which FODMAP, what to look for on ingredient labels, snack suggestions, meal ideas, and other recommended products, brands, apps and resources. The Monash App is an incredible resource and starting place.

Reintroduction Phase:

The goal of the reintroduction phase is to methodically incorporate FODMAP foods back into your diet. During this phase, we gather information on how well you do or do not tolerate specific foods and use this information to guide long-term diet recommendations for you.

During the reintroduction phase one FODMAP food at a time should be added back into your diet. In order to see if you can tolerate a certain type of FODMAP, the food from each group that you reintroduce first will be the food that is most abundant in that FODMAP. For example, if you were adding fructose back in, you could start with honey OR mango, because these two foods contain the highest amounts of natural fructose. If you tolerate these 2 foods, then it’s likely you will tolerate foods with lower amounts of that specific FODMAP. However, you may tolerate some foods in a certain group better than others. For this reason, we typically encourage a slow reintroduction phase with as many individual foods in each group, as possible. This part of the process is critical for long-term success and determining your specific triggers.

It's important to track of all your symptoms throughout the whole process and work with a registered dietitian to guide you through each FODMAP group, the nuances and different scenarios depending on how you feel during this phase.

Is the Low-FODMAP diet right for you?

The low-FODMAP diet may make sense for you if you experience any uncomfortable GI symptoms that interfere with your quality of life and/or have ever been given one of the above diagnoses. Consult with a healthcare provider, such as a functional medicine doctor or dietitian for support, personalization, and potential lab work before starting the diet. I typically find the best success combining this diet with supplement and lifestyle protocols.

If you want to learn more about working together, and if the low-fodmap diet could benefit you, please contact us here and we’ll be in touch with more information.

This article was written in collaboration with Haley Havighurst, RDN. She's also a Cleveland Clinic Dietitian Intern alum!

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