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)
IBS is the most common digestive disorder in Australia, with 1 in 5 adults reporting uncomfortable symptoms.
For many people with this condition, food is a common trigger for symptoms such as stomach pain and bloating.
Interestingly enough, restricting certain foods can dramatically improve these symptoms. That’s where the low FODMAP diet comes in.
This blog post will discuss what the low FODMAP diet is, how it works, and who should try it.
What are FODMAPs?
“FODMAP” stands for “fermentable oligo-, di-, and monosaccharides and polyols”.
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.
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.
In fact, about 60% of people with IBS have reported that these carbs may either cause or worsen their symptoms.
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:
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
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?
While coffee and black and green teas are all low FODMAP foods, caffeinated beverages should be limited on 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.
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
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.
Several other studies concur and suggest that this diet also helps manage flatulence, diarrhea, and constipation.
In fact, a low FODMAP diet is now considered first-line dietary therapy for IBS in many parts of the world.
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.
Several studies indicate that a low FODMAP diet enhances overall quality of life by significantly reducing symptom severity.
Some evidence suggests that by improving digestive symptoms, this diet may also reduce fatigue, depression, and stress while boosting happiness and vitality.
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.
Plus, excluding several types of fruits and vegetables from your diet may lead to vitamin and mineral deficiencies and significantly reduce your fibre intake, which may worsen constipation.
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 disorder.
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 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.
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.
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.
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.
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.
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.
The purpose of this phase is to both:
Identify which types of FODMAPs you tolerate, as few people are sensitive to all of them
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.
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.
It’s best to undertake this step with a 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 .
Stage 3: Personalisation
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.
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.
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.
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.
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:
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.
participating in regular physical exercise
cutting back on caffeinated beverages, since caffeine stimulates the intestines
eating smaller meals
minimising stress (talk therapy may help)
taking probiotics (“good” bacteria normally found in the intestines) to help relieve gas and bloating
avoiding deep-fried or spicy foods
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. Familiarise yourself with low FODMAP menu options so you’ll be prepared when dining out.
Before you embark on the low FODMAP diet, follow the preliminary steps above to increase your chances of successfully managing your digestive symptoms.
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.
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).
Other low FODMAP, protein-rich options for vegetarians are tempeh, tofu, eggs, quinoa, and most nuts and seeds.
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.
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 — Monash University and King’s College London.
3. Consider other life stressors
Diet isn’t the only factor that can aggravate IBS symptoms. Stress is another major contributor.
In fact, no matter how effective your diet is, your symptoms are likely to persist if you’re under severe stress.
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.