Disclosure: Some of the links below are affiliate links, meaning, at no additional cost to you, I will earn a commission if you click through and make a purchase. I have noted these links with an asterisk (*).

If you’re reading this, you’re probably looking for a way to get rid of some frustrating symptoms through changing what you eat. 

You’ve started wondering how many hours you’ve spent in the bathroom over the past month and what else you could’ve done with that time. You’re tired of having to shop for clothes based on how they’ll feel when you’re bloated. You get nervous when you go to a new place and you’re not sure where the bathroom is.

I’m glad you’re here.

There are a trillion elimination diets out there, but the low FODMAP diet is pretty much the only one I recommend for digestive issues outside of those that are dictated by lab results that provide information unique to you (such as allergy testing, the Mediator Release Test for food sensitivities, etc.).

Purpose of the Low FODMAP Diet

The low-FODMAP diet often helps relieve symptoms such as diarrhea, constipation, bloating, gas, and cramping. If you’re looking for an elimination diet for IBS (irritable bowel syndrome), this is a good one to try. (1, 6, 7)

In a nutshell, the low FODMAP diet is an eating plan involving an elimination phase and a challenge phase with the purpose of identifying which fermentable foods are causing your symptoms.

The theory behind this particular IBS elimination diet is that some folks are more sensitive to the side effects of foods that ferment in the gut and so would feel better by reducing their consumption of these foods. Fermentation of foods in the gut is completely normal and desirable, since this means the beneficial bacteria (probiotics) in your intestines are being fed. But sometimes too much or certain types of fermentable foods can trigger uncomfortable symptoms in some people, such as those with unexplained digestive issues or pre-existing gastrointestinal conditions. (4)

This is NOT an immune reaction (allergy or sensitivity), but a difficulty with the digestion and absorption of the food (intolerance).

Enter, low FODMAP diet.

The low FODMAP diet removes highly fermentable foods from your diet and then challenges them in a specific way in order to determine which foods you cannot tolerate. It is temporarily restrictive, with the goal of quickly getting you back to a normal diet that is as unrestricted as possible. It is certainly faster than completing random gluten-free, soy-free, dairy-free, you-name-it-free diets.

Think this might be for you? Keep reading to see the low-FODMAP diet explained.

What are FODMAPs?

The Acronym

First of all, let’s address this crazy acronym. I’ve seen this diet get called the Food Map Diet (which sounds fascinating, doesn’t it??). But it’s actually an acronym that stands for a bunch of science-y terms for certain carbohydrates.

F: Fermentable – OK, so this means we are only dealing with foods that can ferment in the intestines by the bacteria housed there.

O: Oligosaccharides – This term is used to describe a carbohydrate that is composed of a chain of a FEW (oligo) sugars (saccharides).

D: Disaccharides – See where we’re going here? This is a carb that is composed of a chain of TWO (di) sugars.

M: Monosaccharides – You could probably explain this one yourself by now. 🙂 It’s a carbohydrate that is composed of one (mono) sugar.

A: Now stick with me here…this one is really complicated. The ‘A’ stands for….And

P: Polyols – These are sugar alcohols…and no, I’m not talking about the ingredient in your drink that makes you tipsy. Sugar alcohols are added to several foods, especially gum and diet foods, because they taste sweet but are lower in calories. They are also naturally occurring in some fruits and vegetables.

Now, not ALL oligo-, di-, and monosaccharides are super fermentable. This is why the acronym has the descriptor word “Fermentable.” This diet is only concerned with the saccharides that ferment easily. So which are these?

 High FODMAP Carbohydrates

On the low FODMAP diet, we are not concerned with foods that have no carbs or extremely few carbs in the first place, such as meats, fish, poultry, animal fats, and oils. However, grains, fruits, and even vegetables contain some carbohydrates.

Carbohydrates are classified as FODMAPs if they are highly fermentable, hard to digest, or pull water into the intestines. 

I’ve said it once and I’ll say it again: fermentation is completely normal and desirable, since this means the beneficial bacteria (probiotics) in your intestines are being fed. But for some people, higher quantities or certain types of fermentable foods trigger undesirable symptoms.

So what are some specific examples of foods with high amounts of FODMAP carbohydrates?

The FODMAP Categories

The low FODMAP diet plan divides FODMAP carbohydrates into 6 categories:

Lactose: You’ve probably heard of lactose, also called “milk sugar.” This disaccharide is naturally found in dairy products and is in the highest concentrations in milk, evaporated milk, yogurt (frozen and regular), and ice cream.

Fructose: The first source you think of is likely high fructose corn syrup (HFCS). But this monosaccharide also occurs naturally in higher amounts in honey, agave syrup/nectar, cherries, watermelon, sugar snap peas, mango, asparagus, and molasses. If you eat a large amount of other fruit, such as bananas or oranges, you may end up with a high dose of fructose as well.

Mannitol: This is a type of polyol (sugar alcohol) found in mushrooms, celery, snow peas, and the currently popular cauliflower. I cringe when I see more and more cauliflower rice, crusts, and other substitutes, because in large amounts this could end up causing some real digestive distress, even for folks who don’t normally suffer from IBS.

Sorbitol: Another polyol, this time one you may have heard of before. It’s added to most sugar-free gums, which are off-limits during the low FODMAP elimination diet. It is also found naturally in high amounts in prunes, pears, blackberries, nectarines, peaches, apricots, apples, corn, plums, and broccoli.

Oligosaccharides – Gluten-free: This category contains many naturally-gluten-free vegetables, nuts and legumes, such as chicory root/inulin (often added to increase the fiber content of a food), Jerusalem and globe artichokes, the white part of leeks and scallions, split peas, onions, garlic, dried or canned beans, lentils, chickpeas, soybeans, soy milk, pistachios, cashews, tea, ketchup, and Brussels sprouts.

Oligosaccharides – Gluten-containing: Grains that contain gluten tend to be high in oligosaccharides. This means that wheat, rye, and barley are out on the low FODMAP diet. You’ll be avoiding bread made with wheat, whole-wheat, rye, or barley flour, pretzels, couscous, bran cereals, pasta, wheat berries, and bulgur.

If you’re feeling overwhelmed, keep in mind that most of the time folks only have issues with a couple categories long-term. There are conditions that can make you intolerant to all of the categories for a while, such as a bacteria imbalance, damage to the intestinal lining, or inflammation in the intestines. But when these are resolved or managed, FODMAP tolerance often improves as well.

In my practice, I’ve found that the foods clients have the most issues with are dairy, onion, garlic, and beans.

What is the low FODMAP elimination diet?

The low FODMAP elimination diet includes an elimination phase and a challenge phase. During the elimination phase you significantly reduce your consumption of high FODMAP foods. The low-FODMAP diet is NOT a zero-FODMAP diet. It’d be impossible to completely avoid them nor is it recommended. Rather, you avoid high FODMAP foods and large portion sizes of medium-FODMAP foods as best you can. During the challenge phase you test one category of FODMAPs at a time to determine which are troublesome for you.

Timeline

It usually takes about 8-12 weeks to complete the low-FODMAP diet. You start with 2-4 weeks on the elimination phase and then progress to the challenge phase, which usually takes about 6-10 weeks to complete.

Elimination Phase

Your goal during this time is simply to avoid high-FODMAP foods and large portion sizes of medium-FODMAP foods. 

First, take a few minutes to record your current symptoms so you can go back to compare as you progress through the diet. How often do you have a bowel movement? What are they like? Do you have gas? Lots of intestinal noises? What about bloating, pain, fatigue, mood swings, etc.?

Next, go to the grocery store at a time when you are not rushed so you can read labels and pick out the foods that will be your staples for the next couple weeks.

Finally, you’re ready to start the elimination phase! Make sure you circle a date no more than four weeks from your start date when you will progress to the challenge phase, because staying on the elimination phase too long can backfire (more on this later). I also suggest keeping a food and symptom log. Every 5-7 days answer the same questions about your symptoms that you answered before beginning the diet.

After about 10-14 days, evaluate your symptoms.

Best case scenario, you feel like a new human and are nervous about progressing to the challenge phase because you love living without your old symptoms. Buutttt you do it anyways because you don’t want to stay on an elimination diet forever. 🙂

The most common scenario is that you have some symptom relief. This will improve over time as you get better at remembering which foods are high- and low-FODMAP. Continue with the elimination phase and plan to progress to the challenge phase after a couple more weeks. 

Unfortunately, some folks notice very little or no improvement after the elimination phase. If this is you, I’d first take a hard look at what you’ve been eating and drinking to see if perhaps the portions are high-FODMAP. You can also schedule an appointment with a dietitian well-versed in FODMAPs to review your food log.

If you have new symptoms, make sure you’re drinking lots of water and eating snacks or meals regularly (every 3-5 hours).

If you’re pretty sure you’ve been eating low-FODMAP and you haven’t seen improvement on the elimination phase, the cause of your digestive issues likely goes beyond FODMAPs. If this is you, I’d stop the elimination phase and do NOT progress to the challenge phase. Schedule appointments with a gastroenterologist and a dietitian to get input on what to do next.

FODMAP Elimination Phase Schedule

Challenge Phase

During this phase, you will challenge each FODMAP category in order to determine which are symptom triggers for you.

It is very important to realize that you will still be eating low-FODMAP for the duration of the challenge phase, with the exception of the foods you are challenging.

The typical challenge schedule is to try a high FODMAP food in increasing portions for 3 days and then allow yourself 4 days to get back to “baseline” without challenging any other foods. Another option would be to challenge a food in increasing amounts every other day with a “washout” day in between and at either end. Both of these schedules result in you challenging one food per week. If you react strongly to a particular food or if one week your schedule isn’t compatible with challenging a food and therefore risking an IBS episode, feel free to take a “rest week” going back to the baseline low-FODMAP diet between categories.

Thankfully you don’t need to challenge each individual high FODMAP food. But you do need to be strategic with your challenge food choice, because some foods fall into more than one FODMAP category. For example, apples are high in fructose AND sorbitol. If you have symptoms after eating an apple, you can’t be sure if it’s because of the fructose, sorbitol, or both! Choosing foods that only contain one category of FODMAPs makes the challenge phase simpler and faster.

Here’s a sample schedule with recommended challenge foods that only fall into one FODMAP category.

FODMAP Challenge Phase Schedule

Remember, you don’t HAVE to challenge a category if you’re already sure it causes issues for you. For example, you may already know that you are lactose intolerant or have a wheat sensitivity.

Ideally you will complete the challenge phase within a couple months at the longest. At that point, you can evaluate your results:

If you had no issues whatsoever with a category, you can likely enjoy these foods without concern.

If you only had symptoms with high portion sizes within a category, these are your caution foods. You’ll want to remember not to consume these foods in larger amounts or two foods in that same category at a time.

If you had symptoms even with the smallest portion size, continue to avoid that category for now.

Over time, you may discover that it seems like you have an issue with a specific food and not with a whole category. In this case, your reaction to the food is likely not due to its FODMAP content and you probably need allergy or sensitivity testing to determine the cause of your reaction.

Should I try the low FODMAP diet?

As a registered dietitian nutritionist, of course my first answer to this question is to consult an RDN! We can review your individual health history, symptoms, and current diet to help you determine if this would be the best course of action for you. You can schedule an initial consultation with me here.

With that said, the low FODMAP diet is usually most helpful for folks who are having difficulty absorbing nutrients and/or have a condition that makes food move through the intestines more rapidly. Some examples of conditions that often cause symptoms that could be alleviated by a low-FODMAP diet are Crohn’s, Ulcerative Colitis, celiac disease with confirmed damage of the intestinal villi, SIBO (Small Intestinal Bacterial Overgrowth), damage from food poisoning or other infections, or if part of the intestines have been surgically removed. (5)

What are the risks of the low FODMAP diet?

Staying on the diet for longer than 2-3 months can have detrimental effects. Just like any diet that is restricted in some way, the low-FODMAP diet puts you at a higher risk for nutritional deficiencies. (2) Although it’s not a guarantee of preventing deficiencies, I do recommend you take a good quality multivitamin while you are on the diet as somewhat of an insurance policy. Just make sure it doesn’t contain powdered high-FODMAP foods.

And remember that good bacteria we talked about, called probiotics? FODMAPs are a major food source (prebiotics) for them. If that is cut off for a long time, they may start dying off, leading to an imbalance in your microbiome (science word for the bacteria in your body). One of the things these bacteria produce in your intestines are short-chain fatty acids (SCFAs), which we then absorb and benefit from. SCFAs help regulate the metabolism and positively affect cardiovascular markers, among many other benefits. (3) Following the low-FODMAP diet long term puts you at a higher risk for a bacteria imbalance.

Lastly, I must mention that following this or any elimination diet puts you at a higher risk of developing disordered eating patterns. (2) Plus it’s no fun having to eat differently than your friends and family! If you have a history of disordered eating, I recommend you first see a dietitian before attempting the low-FODMAP diet.

The Best FODMAP Resources

1. Low FODMAP Meal Plans

If you’re looking for a low FODMAP diet plan, check out Living Plate Rx*. I’ve collaborated with them to bring you low FODMAP meal plans to take out allll the guesswork. You can try it for free for 3 days and after that subscriptions start out for as little as $9/month. Considering you ideally won’t be on this diet for more than 2-3 months, that’s quite a steal.

Start your free meal plan trial here!*

2. FODMAP Apps

MONASH University FODMAP diet app (Created by the university that researched and developed the low FODMAP diet itself)

Fast FODMAP Lookup & Learn (Free)

Casa de Sante FODMAP app (Free)

Cara: Food, Mood, Poop Tracker (Free; Not specific to FODMAPs, but helpful for food and symptom tracking)

3. Low FODMAP Recipes

Some of my favorite websites for low FODMAP recipes include:

Fun Without FODMAPS

FODMAP Everyday

MONASH Low FODMAP Recipe Index (Recipes approved by the university that developed the diet)

A Little Bit Yummy (More than just recipes, she also has e-courses and a blog chock-full of posts about FODMAPs)

Kate Scarlata (No actual recipes here, but a great resource for suggested products and other info about FODMAPs)

Feed Me Phoebe (Free low FODMAP recipe e-book)

4. FODMAP Books

My top recommendation: The IBS Elimination Diet and Cookbook by Patsy Catsos, MS, RD, LD*

Also helpful: The Complete Low-FODMAP Diet by Sue Shepherd, PhD, and Peter Gibson, MD*

*Disclosure: Some of the links above are affiliate links, meaning, at no additional cost to you, I will earn a commission if you click through and make a purchase. I have noted these links with an asterisk (*).

Medical Disclaimer

The contents of this blog are for informational and educational purposes only and not for the purpose of medical advice. The contents of this blog are not to be used as a substitute for medical advice. While I take efforts to ensure the information on my website is up-to-date, I cannot guarantee that the information on my website reflects the most recent research. As always, consult your doctor and dietitian for personalized medical advice.

Resources:

1. https://www.ncbi.nlm.nih.gov/pubmed/28707437

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5390324/

3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6244749/

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5508768/

5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6265860/

6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5622700/

7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5555627/