Food is a common trigger of digestive symptoms. Interestingly, restricting certain foods can dramatically improve these symptoms in sensitive people.
In particular, a diet low in fermentable carbs known as FODMAPS is clinically recommended for the management of irritable bowel syndrome (IBS).
This article explains what a low-FODMAP diet is, how it works and who should try it.
What Are FODMAPs?
These are the scientific terms used to classify groups of carbs that are notorious for triggering digestive symptoms like bloating, gas and stomach pain.
FODMAPs are found in a wide range of foods in varying amounts. Some foods contain just one type, while others contain several.
The main dietary sources of the four groups of FODMAPs include:
- Oligosaccharides: Wheat, rye, legumes and various fruits and vegetables, such as garlic and onions.
- Disaccharides: Milk, yogurt and soft cheese. Lactose is the main carb.
- Monosaccharides: Various fruit including figs and mangoes, and sweeteners such as honey and agave nectar. Fructose is the main carb.
- Polyols: Certain fruits and vegetables including blackberries and lychee, as well as some low-calorie sweeteners like those in sugar-free gum.
Summary: FODMAPs are a group of fermentable carbs that aggravate gut symptoms in sensitive people. They’re found in a wide range of foods.
Benefits of a Low-FODMAP Diet
A low-FODMAP diet restricts high-FODMAP foods.
The benefits of a low-FODMAP diet have been tested in thousands of people with IBS across more than 30 studies (2).
Reduced Digestive Symptoms
IBS digestive symptoms can vary widely, including stomach pain, bloating, reflux, flatulence and bowel urgency.
Needless to say, these symptoms can be debilitating. One large study even reported that people with IBS said they would give up an average of 25% of their remaining lives to be symptom-free (5).
Fortunately, both stomach pain and bloating have been shown to significantly decrease with a low-FODMAP diet.
Evidence from four high-quality studies concluded that if you follow a low-FODMAP diet, your odds of improving stomach pain and bloating are 81% and 75% greater, respectively (2).
Increased Quality of Life
Luckily, several studies have found the low-FODMAP diet improves overall quality of life (2).
There is also some evidence showing that a low-FODMAP diet may increase energy levels in people with IBS, but placebo-controlled studies are needed to support this finding (6).
Summary: There is convincing evidence for the benefits of a low-FODMAP diet. The diet appears to improve digestive symptoms in approximately 70% of adults with IBS.
Who Should Follow a Low-FODMAP Diet
A low-FODMAP diet is not for everyone. Unless you have been diagnosed with IBS, research suggests the diet could do more harm than good.
Also, most of the research has been in adults. Therefore, there is limited support for the diet in children with IBS.
If you have IBS, consider this diet if you:
- Have ongoing gut symptoms.
- Haven’t responded to stress management strategies.
- Haven’t responded to first-line dietary advice, including restricting alcohol, caffeine, spicy food and other common trigger foods (11).
It is important to be aware that the diet is an involved process. For this reason, it’s not recommended to try it for the first time while traveling or during a busy or stressful period.
Summary: A low-FODMAP diet is recommended for adults with IBS. The evidence for its use in other conditions is limited and may do more harm than good.
How to Follow a Low-FODMAP Diet
A low-FODMAP diet is more complex than you may think and involves three stages.
Stage 1: Restriction
This stage involves strict avoidance of all high-FODMAP foods. If you’re not sure which foods are high in FODMAPs, read this article.
People who follow this diet often think they should avoid all FODMAPs long-term, but this stage should only last about 3–8 weeks. This is because it’s important to include FODMAPs in the diet for gut health.
Some people notice an improvement in symptoms in the first week, while others take the full eight weeks. Once you have adequate relief of your digestive symptoms, you can progress to the second stage.
If by eight weeks your gut symptoms have not resolved, refer to the What If Your Symptoms Don’t Improve? chapter below.
Stage 2: Reintroduction
This stage involves systematically reintroducing high-FODMAP foods.
The purpose of this is twofold:
- To identify which types of FODMAPs you tolerate. Few people are sensitive to all of them.
- To establish the amount of FODMAPs you can tolerate. This is known as your “threshold level.”
In this step, you test specific foods one by one for three days each (1).
It is recommended that you undertake this step with a trained dietitian who can guide you through the appropriate foods. Alternatively, this app can help you identify which foods to reintroduce.
It is worth noting that you need to continue a low-FODMAP diet throughout this stage. This means even if you can tolerate a certain high-FODMAP food, you must continue to restrict it until stage 3.
It is also important to remember that, unlike people with most food allergies, people with IBS can tolerate small amounts of FODMAPs.
Lastly, although digestive symptoms can be debilitating, they will not cause long-term damage to your body.
Stage 3: Personalization
This stage is also known as the “modified low-FODMAP diet.”
In other words, you still restrict some FODMAPs. However, the amount and type are tailored to your personal tolerance, identified in stage 2.
It is important to progress to this final stage in order to increase diet variety and flexibility. These qualities are linked with improved long-term compliance, quality of life and gut health (14).
You can find a video explaining this three-stage process here.
Summary: Many people are surprised to find that the low-FODMAP diet is a three-stage process. Each stage is equally important in achieving long-term symptom relief and overall health and well-being.
Three Things to Do Before You Get Started
There are three things you should do before embarking on the diet.
1. Make Sure You Actually Have IBS
Digestive symptoms can occur in many conditions, some harmless and others more serious.
Unfortunately, there is no positive diagnostic test to confirm you have IBS. For this reason, it is recommended you see a doctor to rule out more serious conditions first, such as celiac disease, inflammatory bowel disease and colon cancer (15).
Once these are ruled out, your doctor can confirm you have IBS using the official IBS diagnostic criteria — you must fulfill all three to be diagnosed with IBS (4):
- Recurrent stomach pain: On average, at least one day per week in the last three months.
- Stool symptoms: These should match two or more of the following: related to defecation, associated with a change in frequency of stool or associated with a change in the appearance of stool.
- Persistent symptoms: Criteria fulfilled for the last three months with symptom onset at least six months before diagnosis.
2. Try First-Line Diet Strategies
The low-FODMAP diet is a time- and resource-intensive process.
This is why in clinical practice it is considered second-line dietary advice and is only used in a subset of people with IBS who don’t respond to first-line strategies.
More information about first-line dietary advice can be found here.
3. Plan Ahead
The diet can be difficult to follow if you are not prepared. Here are some tips:
- Find out what to buy: Ensure you have access to credible low-FODMAP food lists. See below for a list of where to find these.
- Get rid of high-FODMAP foods: Clear your fridge and pantry of these foods.
- Make a shopping list: Create a low-FODMAP shopping list before heading to the grocery store, so you know which foods to purchase or avoid.
- Read menus in advance: Familiarize yourself with low-FODMAP menu options so you’ll be prepared when dining out.
Summary: Before you embark on the low-FODMAP diet, there are several things you need to do. These simple steps will help increase your chances of successfully managing your digestive symptoms.
A Low-FODMAP Diet Can Be Flavorful
Garlic and onion are both very high in FODMAPs. This has led to the common misconception that a low-FODMAP diet lacks flavor.
While many recipes do use onion and garlic for flavor, there are many low-FODMAP herbs, spices and savory flavorings that can be substituted instead.
It is also worth highlighting that you can still get the flavor from garlic using strained garlic-infused oil, which is low in FODMAPs.
This is because the FODMAPs in garlic are not fat-soluble, meaning the garlic flavor is transferred to the oil, but the FODMAPs aren’t.
You can find a more extensive list here.
Summary: Several popular flavors are high in FODMAPs, but there are many low-FODMAP herbs and spices that can be used to make flavorsome meals.
Can Vegetarians Follow a Low-FODMAP Diet?
A well-balanced vegetarian diet can be low in FODMAPs. Nonetheless, following a low-FODMAP diet if you are a vegetarian can be more challenging.
This is because high-FODMAP legumes are staple protein foods in vegetarian diets.
That said, you can include small portions of canned and rinsed legumes in a low-FODMAP diet. Serving sizes are typically about 1/4 cup (64 grams).
There are also many low-FODMAP, protein-rich options for vegetarians, including tempeh, tofu, eggs, Quorn (a meat substitute) and most nuts and seeds (19).
Summary: There are many protein-rich vegetarian options suitable for a low-FODMAP diet. Therefore, there is no reason why a vegetarian with IBS cannot follow a well-balanced low-FODMAP diet.
A Sample Low-FODMAP Shopping List
Here is a simple shopping list to get you started.
- Protein: Beef, chicken, eggs, fish, lamb, pork, prawns and tofu
- Whole grains: Brown rice, buckwheat, maize, millet, oats and quinoa
- Fruit: Bananas, blueberries, kiwi, limes, mandarins, oranges, papaya, pineapple, rhubarb and strawberries
- Vegetables: Bean sprouts, bell peppers, carrots, choy sum, eggplant, kale, tomatoes, spinach and zucchini
- Nuts: Almonds (no more than 10 per sitting), macadamia nuts, peanuts, pecans, pine nuts and walnuts
- Seeds: Linseeds, pumpkin, sesame and sunflower
- Dairy: Cheddar cheese, lactose-free milk and Parmesan cheese
- Oils: Coconut oil and olive oil
- Beverages: Black tea, coffee, green tea, peppermint tea, water and white tea
- Condiments: Basil, chili, ginger, mustard, pepper, salt, white rice vinegar and wasabi powder
Additionally, it’s important to check the ingredients list on packaged foods for added FODMAPs.
Food companies may add FODMAPs to their foods for many reasons, including as prebiotics, as a fat substitute or as a lower-calorie substitute for sugar.
Summary: Many foods are naturally low in FODMAPs. That said, many processed foods have added FODMAPs and should be limited.
What If Your Symptoms Don’t Improve?
The low-FODMAP diet does not work for everyone with IBS. Around 30% of people don’t respond to the diet (20).
Fortunately, there are other non-diet-based therapies that may help. Talk to your doctor about alternative options.
That said, before you give up on the low-FODMAP diet, you should:
1. Check and Recheck Ingredient Lists
Prepackaged foods often contain hidden sources of FODMAPs.
Common culprits include onion, garlic, sorbitol and xylitol, which can trigger symptoms even in small amounts.
2. Consider the Accuracy of Your FODMAP Information
There are many low-FODMAP food lists available online.
3. Think About Other Life Stressors
Diet is not the only thing that can aggravate IBS symptoms. Stress is another major contributor (21).
In fact, no matter how effective your diet, if you are under severe stress, your symptoms are likely to persist.
Summary: The low-FODMAP diet does not work for everyone. However, there are common mistakes worth checking before you try other therapies.
The Bottom Line
The low-FODMAP diet can dramatically improve digestive symptoms, including those in people with IBS.
However, not everyone with IBS responds to the diet. What’s more, the diet involves a three-stage process that can take up to six months.
And unless you need it, the diet may do more harm than good, since FODMAPs are prebiotics that support the growth of beneficial bacteria in your gut.
Nonetheless, this diet could be truly life-changing for those struggling with IBS.