A Beginner’s Guide to the Low FODMAP Diet

A diet low in fermentable carbs, called the low FODMAP diet, is often recommended to manage irritable bowel syndrome (IBS) (1, 2).

IBS is the most common digestive disorder in the United States. For many people with this condition, food is a common trigger for symptoms such as stomach pain and bloating (1, 3).

Interestingly enough, restricting certain foods can dramatically improve these symptoms. That’s where the low FODMAP diet comes in.

This article explains what the low FODMAP diet is, how it works, and who should try it.

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What are FODMAPs?

“FODMAP” stands for “fermentable oligo-, di-, and monosaccharides and polyols” (1, 2).

These are nondigestible short-chain carbs that are osmotically active, meaning they force water into your digestive tract.

Additionally, because they’re nondigestible, your gut bacteria ferment them, increasing gas and short-chain fatty acid production (1).

Therefore, FODMAPs are notorious for triggering digestive symptoms such as bloating, gas, stomach pain, and altered bowel habits varying from constipation to diarrhea or a combination of both (1, 3).

In fact, about 60% of people with IBS have reported that these carbs may either cause or worsen their symptoms (1).

FODMAPs are found in varying amounts in a wide range of foods. Some foods contain just one type, while others have several. The primary dietary sources of the four groups of FODMAPs are (3, 4):

• Oligosaccharides: wheat, rye, nuts, legumes, artichokes, garlic, and onion
• Disaccharides: lactose-containing products such as milk, yogurt, soft cheese, ice cream, buttermilk, condensed milk, and whipped cream
• Monosaccharides: fructose-containing foods, including fruits such as apples, pears, watermelon, and mango and sweeteners such as honey, agave nectar, and high fructose corn syrup
• Polyols: mannitol and sorbitol in apples, pears, cauliflower, stone fruits, mushrooms, and snow peas, as well as xylitol and isomalt in low calorie sweeteners, such as those in sugar-free gum and mints

Summary

FODMAPs are a group of fermentable carbs that aggravate gut symptoms in people who are sensitive to them. They’re found in a wide range of foods.

What foods can you eat on a low FODMAP diet?

Habitual FODMAP intake from a regular or high FODMAP diet ranges from 0.5–1 ounce (15–30 grams) of these carbs per day.

Conversely, a low FODMAP diet aims to limit your intake to 0.02 ounces (0.5 grams) per sitting — an extremely low amount that translates to 0.08–0.1 ounces (2.5–3 grams) per day if you follow the suggestion of eating small, frequent meals (1).

Luckily, many foods are naturally low in FODMAPs. Here’s a list of foods you can eat while following a low FODMAP diet (5, 6):

• Proteins: beef, chicken, eggs, fish, lamb, pork, prawns, tempeh, and tofu
• Whole grains and starches: white and brown rice, lentils, corn, oats, quinoa, cassava, and potatoes
• Fruit: blueberries, raspberries, pineapple, honeydew melon, cantaloupe, kiwi, limes, guava, starfruit, grapes, and strawberries
• Vegetables: bean sprouts, bell peppers, radishes, bok choy, carrots, celery, eggplant, kale, tomatoes, spinach, cucumber, pumpkin, and zucchini
• Nuts: almonds (no more than 10 per sitting), macadamia nuts, peanuts, pecans, pine nuts, and walnuts
• Seeds: pumpkin, sesame, and sunflower seeds, as well as linseeds
• Dairy: lactose-free milk, Greek yogurt, and Parmesan, Colby, cheddar, and mozzarella cheeses
• Oils: coconut and olive oils
• Beverages: peppermint tea and water
• Condiments: cumin, saffron, cinnamon, paprika, coriander, cardamom, soy sauce, fish sauce, some chile-based products, ginger, mustard, pepper, salt, white rice vinegar, and wasabi powder

While coffee and black and green teas are all low FODMAP foods, caffeinated beverages are usually discouraged a low FODMAP diet because caffeine tends to be a trigger for those with IBS.

Additionally, it’s important to check the ingredient lists on packaged foods for added FODMAPs. Manufacturers may add FODMAPs to their foods for many reasons, including as prebiotics, fat substitutes, or low calorie sugar substitutes (3, 5).

Summary

Many foods are naturally low in FODMAPs. However, when following a low FODMAP diet, you should be mindful of processed foods, which may contain added FODMAPs.

Benefits of a low FODMAP diet

A low FODMAP diet restricts high FODMAP foods. Scientific evidence suggests that this eating pattern may benefit people with IBS.

May reduce digestive symptoms

IBS symptoms vary widely but include stomach pain, bloating, reflux, flatulence, and bowel urgency. Needless to say, these symptoms can be debilitating.

Notably, a low FODMAP diet has been shown to decrease both stomach pain and bloating.

Evidence from four high quality studies concluded that a low FODMAP diet leads to an 81% and 75% greater chance of relieving stomach pain and bloating, respectively (7).

Several other studies concur and suggest that this diet also helps manage flatulence, diarrhea, and constipation (1, 2, 5, 8, 9).

In fact, a low FODMAP diet is now considered first-line dietary therapy for IBS in many parts of the world (10).

May improve your quality of life

People with IBS often report a reduced quality of life associated with severe digestive symptoms. These symptoms may affect social interactions and even work performance (1, 2, 9).

Several studies indicate that a low FODMAP diet enhances overall quality of life by significantly reducing symptom severity (2, 7, 11).

Some evidence suggests that by improving digestive symptoms, this diet may also reduce fatigue, depression, and stress while boosting happiness and vitality (12).

Summary

Studies indicate several benefits of a low FODMAP diet for people with IBS, including improved digestive symptoms and enhanced quality of life.

Who should follow a low FODMAP diet?

A low FODMAP diet is not for everyone. Unless you’ve been diagnosed with IBS, this diet may do more harm than good.

That’s because most FODMAPs are prebiotics, which means they support the growth of beneficial gut bacteria. Therefore, eliminating them may harm your intestinal bacteria, which directly affect your overall health (1).

Plus, excluding several types of fruits and vegetables from your diet may lead to vitamin and mineral deficiencies and significantly reduce your fiber intake, which may worsen constipation (1, 2, 13).

Therefore, to ensure nutritional adequacy and avoid potential imbalances, you should follow this diet only under the guidance of a dietitian with expertise in digestive disorders (1, 3).

If you have IBS, consider this diet if you (9):

• have ongoing gut symptoms
• haven’t responded to stress management strategies
• haven’t responded to first-line dietary advice, including adjusting meal size and frequency and restricting your intake of alcohol, caffeine, spicy foods, and other common trigger foods

While there’s some speculation that the diet may benefit other conditions, including diverticulitis and exercise-induced digestive issues, more research is needed (14, 15).

Since this diet is an involved process, you shouldn’t try it for the first time while traveling or during a busy or stressful period.

Summary

Although a low FODMAP diet may help adults with IBS, you should follow it only under the supervision of a professional — and only after trying other dietary treatments first.

How to follow a low FODMAP diet

A low FODMAP diet is complex and involves three stages (16).

Stage 1: Restriction

This stage involves strict avoidance of all high FODMAP foods.

People who follow this diet often think they should avoid all FODMAPs long term, but this stage should last only 4–8 weeks. That’s because FODMAPs are so important for gut health (1, 3).

Some people notice an improvement in symptoms in the first week, while in others improvements take the full 8 weeks. Up to 75% of people following this diet report improved symptoms within 6 weeks (3).

Once you have adequate relief from your digestive symptoms, you can progress to the second stage.

Stage 2: Reintroduction

This stage involves systematically reintroducing high FODMAP foods. Although its duration varies from one person to another, it typically lasts 6–10 weeks (9).

The purpose of this phase is twofold (1, 13):

• to identify which types of FODMAPs you tolerate, as few people are sensitive to all of them
• to establish the amount of FODMAPs you can tolerate — also known as your “threshold level”

In this step, you test small amounts of specific foods one by one for 3 days.

It’s advised to remain on a strict low FODMAP diet while testing each food and wait 2–3 days before reintroducing a new one to avoid additive or crossover effects (13).

Once you establish your minimal tolerance, you may evaluate your tolerance to larger doses, increased intake frequency, and combinations of high FODMAP foods — but remember to take breaks of 2–3 days after each test (13).

It’s best to undertake this step with a registered dietitian who can guide you through the appropriate foods.

It’s also important to remember that, unlike people with most food allergies, who must completely avoid certain allergens, people with IBS can tolerate small amounts of FODMAPs (1).

Stage 3: Personalization

This stage is also known as the “modified low FODMAP diet” because you still restrict some FODMAPs but reintroduce well-tolerated ones to your diet (9).

In other words, during this stage, the amount and type of FODMAPs are tailored to the personal tolerance you identified in stage 2.

The low FODMAP diet is neither a one-size-fits-all approach nor a lifelong diet. The ultimate goal is to reintroduce high FODMAP foods at your personal tolerance levels (3).

It’s essential to progress to this final stage to increase diet variety and flexibility. These qualities are linked to improved long-term compliance, quality of life, and gut health (1, 3).

Summary

The low FODMAP diet is a three-stage process. Each stage is equally important in achieving long-term symptom relief and overall health.

Three things to do before you get started

Follow these three steps before embarking on a low FODMAP diet.

1. Make sure you have IBS

Digestive symptoms occur in many conditions, some harmless and others more serious.

IBS symptoms are also common in other chronic conditions, such as celiac disease, inflammatory bowel disease, defecatory disorders, and colon cancer (3).

Thus, you should consult a doctor to rule out these other conditions. Once these are ruled out, your doctor can confirm that you have IBS using the official IBS diagnostic criteria. You must fulfill all three of the following conditions to be diagnosed with IBS (17, 18):

• Recurrent stomach pain. On average, your pain has occurred at least 1 day per week in the last 3 months.
• Stool symptoms. These should match two or more of the following: related to defecation, associated with a change in stool frequency, or associated with a change in the appearance of stool.
• Persistent symptoms. You’ve experienced consistent symptoms for the last 3 months, with symptom onset at least 6 months before diagnosis.

2. Try lifestyle and dietary modification strategies

The low FODMAP diet is a time- and resource-intensive process.

This is why it’s still considered second-line dietary advice in some countries and is used only for people with IBS who don’t respond to first-line strategies.

3. Plan ahead

It can be challenging to follow the low FODMAP diet’s limitations. Here are some tips to help you prepare:

• Find out what to buy. Ensure you have access to credible low FODMAP food lists.
• Get rid of high FODMAP foods. Clear your fridge and pantry of these foods to avoid any mistakes.
• 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, follow the preliminary steps above to 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 call for onion and garlic, you can instead choose from many low FODMAP herbs, spices, and flavorings.

Plus, you can still get the flavor of garlic by using strained garlic-infused oil, which is low in FODMAPs. This is because the FODMAPs in garlic aren’t fat-soluble, so the flavor is transferred to the oil, but the FODMAPs aren’t (6).

Other low FODMAP condiment suggestions

The following spices, herbs, and condiments make great low FODMAP seasonings (6):

• chives
• some chiles
• fenugreek
• ginger
• lemongrass
• mustard seeds
• pepper
• saffron
• turmeric

Summary

You can use many low FODMAP herbs and spices — including ginger, pepper, chives, and some chiles — to make flavorful meals.

Can vegetarians follow a low FODMAP diet?

A well-balanced vegetarian diet can be low in FODMAPs. Nonetheless, following a low FODMAP diet may be more challenging if you don’t eat meat.

This is because high FODMAP foods such as legumes are staple plant-based proteins in vegetarian diets (6).

Nonetheless, you can include small portions of canned, rinsed legumes in a low FODMAP diet because they tend to be lower in FODMAPs than boiled legumes. The serving size is typically about 1/4 cup (64 grams) (5).

Other low FODMAP, protein-rich options for vegetarians are tempeh, tofu, eggs, quinoa, and most nuts and seeds (5, 6).

Summary

Many protein-rich vegetarian options are suitable for a low FODMAP diet. Therefore, a balanced low FODMAP diet can easily be made vegetarian.

What if your symptoms don’t improve?

The low FODMAP diet doesn’t work for everyone with IBS. In fact, around 30% of people don’t respond to the diet at all (9).

Fortunately, other non-dietary therapies may help. Talk with your doctor if you want to explore alternative options.

That said, before you give up on the low FODMAP diet, take the following steps.

1. Check and recheck ingredient lists

Packaged 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

Many low FODMAP food lists exist online.

However, only two universities provide comprehensive, validated FODMAP food lists and apps — King’s College London and Monash University.

3. Consider other life stressors

Diet isn’t the only factor that can aggravate IBS symptoms. Stress is another major contributor (1, 19).

In fact, no matter how effective your diet is, your symptoms are likely to persist if you’re under severe stress.

Summary

A low FODMAP diet doesn’t work for everyone. However, there are common mistakes worth checking before you try other therapies.

The bottom line

The low FODMAP diet may dramatically improve digestive symptoms in people with IBS.

However, the diet involves a three-stage process that may take up to 8 weeks to produce improvements, and not everyone with IBS responds to it.

Unless you need it, this diet may do more harm than good, because FODMAPs are prebiotics that support gut health. What’s more, high FODMAP foods are major dietary sources of vitamins and minerals.

Nonetheless, this diet may vastly improve your quality of life if you have IBS.