What is the low-FODMAP diet?
FODMAP is an umbrella term for a group of carbohydrates that your small intestine struggles to absorb. You find them in everyday foods: wheat, onion, garlic, legumes, dairy and certain fruits. All foods that most people eat without a second thought.
When people have gut symptoms, like bloating, abdominal pain or diarrhoea, they go looking for possible causes. Sometimes it turns out they react to certain beans, that they don't tolerate dairy well, or that onion and garlic trigger symptoms. The more aware you become of how food affects you, the longer the list of foods to avoid can grow.
While searching for a solution to your symptoms, or perhaps on the advice of a doctor or dietitian, you may come across the FODMAP diet. The idea behind it is simple: take away the carbohydrates that irritate your gut and things calm down. It's not ideal, but it makes the symptoms bearable. So you carry on like this.
And that's exactly where the biggest misunderstanding begins. Because the low-FODMAP diet was never meant to be a strict diet you follow forever. It's meant as a temporary experiment on your own gut, in three phases. First you take these carbohydrates out of your food as much as possible for four to six weeks. Then you add them back one by one, so you find out what you react to and how much of it your body can handle. And finally you only leave out what truly gives you symptoms. Three phases. But in practice, most people never get past the first one.
Which foods are high in FODMAPs?
FODMAP stands for a few groups of carbohydrates with difficult names. It's the fermentable sugars in foods like wheat, onion, garlic and legumes. The milk sugar (lactose) in dairy. The fruit sugar (fructose) in certain fruits. And the sugar alcohols in stone fruits and sugar-free sweets.
Monash University in Australia, where the low-FODMAP diet was developed, has tested hundreds of foods in the lab. These are the best-known examples, by group:
| Food group | High FODMAP (limit) | Low FODMAP (fine) |
|---|---|---|
| Vegetables | garlic, onion, leek, mushrooms, asparagus, green peas, red bell pepper | carrot, cucumber, courgette, aubergine, green beans, green bell pepper, potato |
| Fruit | apple, pear, mango, cherries, peach, plum, watermelon, dried fruit | orange, mandarin, kiwi, pineapple, blueberries, cantaloupe melon |
| Grains and bread | bread and pasta made from wheat, rye and barley | oats, rice, quinoa, corn, rice or corn pasta, sourdough spelt bread |
| Dairy | milk, yoghurt, custard, ice cream, fresh soft cheeses | lactose-free milk, almond milk, hard aged cheeses like mature cheddar and parmesan |
| Protein | legumes like chickpeas, lentils and kidney beans | meat, fish, eggs, firm tofu, tempeh |
| Nuts | cashews, pistachios | walnuts, peanuts, macadamias, pumpkin seeds |
What often goes wrong here: people read a list like this as right or wrong. Everything on the left goes out, everything on the right comes in. But that's not how it works. Whether something has too much FODMAP depends on the portion, and on how your body reacts. For one person, a little garlic in a dish is fine, while a whole clove causes symptoms. For another, even a little garlic can already cause symptoms. And on top of a single dish, there's your intake across the whole day, where several moderate sources can add up to too much. So it's not a question of forbidden or allowed, but of how much.
A nice example is garlic itself. The clove is full of FODMAPs, but garlic-infused oil is not. The molecules that cause the symptoms dissolve in water, not in oil. Fry a few whole cloves in oil and take them out again, and you keep the flavour without the FODMAPs. And a firm, not-too-ripe banana sits comfortably in the right-hand column, while an overripe banana holds more fruit sugar and moves to the left.
How does the low-FODMAP diet work?
To understand why it works, you need to know what happens to these carbohydrates when you do eat them. Normally, when your digestion works well, your food is broken down in your stomach and small intestine, and most of the nutrients are absorbed in the small intestine.
When digestion or absorption is disrupted, FODMAPs can stay behind in your small intestine. There they draw in water, and eventually arrive in your large intestine almost undigested. This is where your gut flora lives, an ecosystem of millions of bacteria, and they do what they're good at: normally they ferment the fibre from fruit and vegetables, but now they ferment the undigested carbohydrates too.
That fermentation produces gas. The gas, together with the water that's been drawn in, stretches your gut from the inside, which can send a pain signal to your brain. You feel it as a belly that's tight and bloated, as cramps, and as trousers that suddenly pinch in the evening when they fit just fine that morning.
Take the FODMAPs away and there's far less to ferment. Less fermentation means less gas, less stretching and less irritation. And so fewer symptoms. That's how simple the mechanism is, and it's exactly why it brings relief for so many people.
Does the low-FODMAP diet work?
Yes, and it's well supported. A large overview of sixteen meta-analyses, together covering nearly ten thousand people with irritable bowel syndrome, shows that the low-FODMAP diet reduces the severity of symptoms and improves quality of life.
But the fact that your symptoms ease doesn't mean your gut has healed. And that's the part you won't read on most FODMAP websites. You've taken away the food your gut was reacting to, so things have settled down. What lies underneath, though, hasn't changed: your digestion and the absorption of nutrients are still disrupted, your gut flora may still be off, and the restriction doesn't make it any stronger.
What that means in practice: the low-FODMAP diet helps you feel better, but it doesn't make your gut healthier. It quiets the signal, but it doesn't solve the cause of your symptoms.
The downsides of the low-FODMAP diet (that you rarely hear about)
The low-FODMAP diet is often presented as the solution for IBS. But it has downsides that are rarely mentioned.
The diet is strict, and socially difficult. Eating out, a birthday, dinner at a friend's place. The moment you're not cooking for yourself, it gets complicated. That costs energy, and the feeling of being a burden, of wondering whether you'll be able to eat somewhere and whether anyone has thought of you, creates stress. And stress happens to be something your gut reacts to as well.
Following the diet long term can also build up nutrient deficiencies. After all, you're leaving out a big part of your normal food.
And then the most important one, the part that's almost never mentioned: by cutting out a whole range of high-FODMAP foods, you also cut out foods that matter for your good gut bacteria. Because it's the fibre in fruit and vegetables that your gut flora lives on. Take it away for a long time and those bacteria don't get what they need, and the diversity in your gut goes down. So you remove one trigger for your symptoms, but in the long run your gut flora doesn't grow stronger. Often the opposite happens.
And that brings me back to the beginning. The diet is meant to be temporary, three phases over a few months. But because the symptoms come back the moment you reintroduce something, many people stay stuck in phase one out of fear. When the list of what you can still eat is small, at least you know where you stand and how your body reacts. The downside is that you may follow a strict diet for years, when that was never the intention.
How we see it
In our practice, we see the low-FODMAP diet as a tool for people who want to discover what their body reacts to through an elimination diet. It is not the destination. It can give you temporary calm, and that calm is genuinely valuable. But that's where the real question begins.
Because why does your gut react so strongly to food that millions of people eat without any problem? A healthy gut can handle garlic, onion or an apple just fine. If that normal food gives you symptoms, that's a signal. A signal that something underneath is off.
That something could be a lot of things: a gut flora that's out of balance, a bacterial overgrowth, a parasite, or a food intolerance where your immune system reacts to certain foods. A stool test or a food intolerance test can make those kinds of causes visible, instead of leaving you to keep guessing.
Every one of our practitioners has a history of gut complaints themselves. For us, that was the start of a journey to understand our own bodies, to recover, and the beginning of the work we now do. We got rid of those symptoms by understanding what our gut needed and addressing the cause. The same principles apply whether you've been diagnosed with irritable bowel syndrome, Crohn's disease or ulcerative colitis, or have no explanation or diagnosis for your symptoms at all.
In closing
The low-FODMAP diet works. But it cures nothing.
That's no reason not to do it. It's a reason to look further once you start feeling better. So my advice is this: use the low-FODMAP diet the way it was meant to be used. As temporary relief that gives you room to ask the real question: what does my gut need to handle normal food again?
Do you recognise this, and are you ready to look beyond just quieting your symptoms? You don't have to do it on your own. In a free intro call we take the time for your story: where you are now, what you've already tried, and what your gut really needs. Together we look at the cause, and at the first step that fits you. No obligations and no sales pitch, just an honest conversation where you finally feel heard.