What is a low FODMAP diet?

24th August, 2022 • 11 min read

You’re out for dinner with friends, catching up and enjoying the delicious food when suddenly, the dreaded symptoms hit you. It starts with a bloated feeling, then the cramps arrive, followed by embarrassing wind noises, and then it’s a mad dash to the toilet with diarrhoea.

Sound familiar? If you often get an upset stomach after eating, you might be wondering: what is a low FODMAP diet and could it be the answer to your problems?

It’s an elimination diet that helps you work out which foods are causing your stomach symptoms – so that you can avoid those foods in future. You spend 2-6 weeks cutting out high FODMAP foods, re-introducing them to see if they cause you problems, and then working out which ones you want to get rid of going forward, based on how you get on.

“The low FODMAP diet is thought to be an effective diet for treating

irritable bowel syndrome (IBS)
symptoms – and that’s good news for women because IBS is almost twice as likely to affect women than men. The symptoms can be painful, embarrassing, inconvenient and exhausting,” says Dr Adiele Hoffman, a doctor at Healthily.

Read on to find out which foods are high FODMAP, which foods are low FODMAP, how the diet actually works and why you always need to speak to a medical professional before making any changes to what you're eating.

What does FODMAP mean?

‘FODMAP’ stands for ‘fermentable, oligosaccharides, disaccharides, monosaccharides and polyols.’ These are a group of simple and complex carbohydrates (or sugars) which the gut doesn’t absorb well. It’s thought that they can draw fluid into the gut and become fermented by the bacteria that normally live there, causing unpleasant digestive symptoms in some people. They are found in some fruits, veg, dairy, proteins, breads and cereals.

Here, we take a closer look at FODMAPs:

  • fermentable – foods that your gut bacteria feed on, such as beans and pulses, which are turned into gas in a process called fermentation
  • oligosaccharides – these are known as prebiotics, they feed the good bacteria in your gut. They include onions, garlic and some wheat products
  • disaccharides – foods that contain lactose (a fermentable sugar) found in dairy milk
  • monosaccharides – these foods contain fructose, the sugar found in fruit, but not all fruits are monosaccharides. This is because some are higher in fructose (apples and grapes), and some are lower (blueberries, strawberries and bananas)
  • polyols – often called sugar alcohols. They’re included in artificial sweeteners, such as sorbitol and xylitol, and they can be found naturally in some fruits as well, including apples and nectarines

What conditions can the low FODMAP diet treat?

The low FODMAP diet is often used to help people who have IBS – research showing that it can help reduce symptoms, particularly diarrhoea, bloating and abdominal pain, is encouraging. But more studies are needed to know if this improvement continues on beyond the initial ‘elimination’ phase. But the diet can sometimes be helpful for the symptoms of other conditions too, including:

  • coeliac disease
    – some people with coeliac disease find their symptoms improve after following a gluten-free diet, but this doesn’t always work. It’s thought an overlap in the symptoms of coeliac disease and IBS may mean some issues experienced by people with coeliac disease are down to IBS, which is when following a low FODMAP diet can be helpful for some people
  • small intestinal bacterial overgrowth (SIBO) – the low FODMAP diet can sometimes be recommended if you’ve had SIBO and taken a dose of antibiotics to treat it. SIBO, as the name suggests, is when you get an overgrowth of bacteria in your small intestine and it’s thought to lead to IBS-type symptoms. Sticking to a low FODMAP diet may help ‘starve’ any bacteria that could be left in the small intestine, but this is still theory as there’s no research that’s looked into it yet
  • inflammatory bowel disease (IBD)
    – the low FODMAP diet has been found to reduce irritable bowel-type symptoms in people with IBD. It’s also thought it might reduce inflammation linked to IBD, but we need more evidence to prove this

Find useful information on other areas of gut health with our

complete Healthy Gut Guide

What are low FODMAP foods?

Low FODMAP foods are easier for your gut to absorb because they’re lower in simple and complex sugars. But how do you know which foods are low FODMAP and which are high FODMAP?

It’s not always as simple as labelling a food as one or the other. Sure, some items fall neatly into one group, but other foods can be low or high FODMAP, depending on how much of them you eat.

Think of it this way – all foods contain FODMAPs in different amounts. Some are very concentrated, but others have much smaller amounts of FODMAPs in, even in a really large portion. If you have IBS, you probably have a dose response to FODMAPs, which means you’re likely to get tummy symptoms when you’ve eaten a certain amount of one food or another, and these levels are different for everyone.

To make things a little clearer, Monash University has come up with the

Monash FODMAP App
, which offers a traffic light rating of foods based on a full serving and a half serving. Lots of foods labelled ‘red’ on a full portion can be ‘green’ or ‘amber’ at half a portion, and the same can happen with ‘amber’ foods too.

You’re probably now wondering which of your favourite foods are considered low FODMAP… Is corn low FODMAP, for example? It is, if you don’t eat a full portion of it. Are carrots, broccoli and tomatoes low FODMAP? Yes, yes and yes.

Other foods that fall comfortably into the low FODMAP category are:

  • eggs and non-processed meat
  • some cheeses such as brie, Camembert, cheddar and feta
  • dairy-free milks like almond milk
  • snacks like popcorn, if the product doesn’t contain higher FODMAP ingredients like molasses or high fructose corn syrup
  • natural peanut butter in servings smaller than 2 tablespoons
  • grains such as rice, quinoa and oats
  • sourdough bread (other bread is high FODMAP)
  • some vegetables including aubergine (eggplant), potatoes, peas, cucumbers and courgette (zucchini)
  • some fruits such as grapes, oranges, strawberries, blueberries and pineapple

What are high FODMAP foods?

High FODMAP foods are high in simple and complex sugars. Your gut doesn't absorb them as well as low FODMAP foods, so they tend to spend longer in your gut. Because of this, the foods attract water and become fermented by bacteria. In people with IBS, having an overactive gut can cause:

  • bloating
  • cramping
  • a swollen tummy
  • wind and diarrhoea

Foods that fall cleanly into the high FODMAP category include:

  • milk, yoghurt and ice cream
  • most wheat and barley-based products such as cereal and bread, although
  • sourdough bread is a low FODMAP food
  • beans and lentils
  • jarred and tinned products such as pickles and baked beans
  • some vegetables, such as artichokes, asparagus, onions and garlic
  • some fruits, including apples, cherries, pears and peaches

But as we’ve explained above, some foods considered high FODMAP and ‘red’ on the traffic light system (when eating a full serving) can be labelled ‘green’, if they’re eaten as a half portion.

Examples of these types of foods and the portions you should eat them in include:

  • pasta – ½ cup cooked, 74g
  • wholemeal bread – 1 slice, 24g
  • butter beans (canned) – ¼ cup, 35g
  • sweetcorn – ½ cob, 38g
  • snow peas – 5 pods, 16g
  • avocado – 1/8 avocado, 30g
  • raisins – 1 tablespoon, 13g
  • almonds – 10 nuts, 12g
  • chocolate chip biscuits – 1 biscuit, 12g

Are high FODMAP foods unhealthy or harmful?

Not at all. High FODMAP foods can and should be part of a healthy diet because many of them contain a lot of fibre, which is a great way to keep your digestive system working well.
But if your tummy is sensitive to these foods, the uncomfortable symptoms they cause might stop you from getting on with your day and enjoying life, so finding a balance that’s right for you is important.

How long does the low FODMAP diet last?

The aim of a low FODMAP diet is to avoid high FODMAP foods for a short time and slowly reintroduce them. This can help you work out which foods are causing your problems and which ones you might want to limit, or avoid completely, as you start eating again as normal.

The elimination phase isn’t meant to last longer than 6 weeks because it’s quite restrictive, but doing it with help from your doctor or a dietitian can make sure you’re getting the right nutrition along the way.

The low FODMAP diet follows 3 steps:

  • step 1 – you stop eating all high FODMAP foods for 2 to 6 weeks. Your doctor or dietician should give you a shopping list of what you can eat, recipe ideas and portion sizes for different foods
  • step 2 – with the help of your doctor or a dietician, you slowly reintroduce high FODMAP foods one at a time (every 3 days if you don’t notice any symptoms) to spot which ones are causing you problems It might be that you don’t have an issue with all the foods on the high FODMAP list because trigger foods vary from person to person
  • step 3 – once you’ve worked out which foods cause your symptoms, you can avoid these foods, or limit them in your everyday diet

But don’t feel disheartened if there is a list of foods you need to avoid long-term. There are plenty of ways you can still get the same flavours and tastes into your meals, even if you have to cut out specific items.

Find low FODMAP recipes

If you’re looking for low FODMAP food inspiration, why not try flicking through the online resources below. Each has plenty of delicious recipes to choose from, as well as helpful tips to make sure you’re eating a full a diet as possible:

FODMAP diet for IBS - how it worked for me

Our health stories are designed to give women's voices more space and time to really share their experiences and tips with you. If you don't have time to watch the whole of Sarah's video right now, you can:

  • just listen to the audio while you go about your day
  • bookmark this page to come back to when you've got a few minutes

When to see a doctor

The trouble is, it can be all too easy to suffer in silence – and that’s partly down to stigma. Research from the charity Guts UK found that 58% of people are embarrassed to talk about digestive symptoms, while just over half of people (51%) put off getting medical advice about their tummy issues.

If you think high FODMAP foods may be causing your stomach sensitivity, try using our

Smart Symptom Checker
to help you work out your next steps.

  • always speak to a doctor if you think you may have IBS. They will ask you some questions and may refer you for tests to work out if it’s IBS, or something else that’s causing your symptoms
  • see a doctor urgently if you notice any
    red flag symptoms
  • if you have IBS and want to try the low FODMAP diet, your doctor might refer you to a dietitian who will explain more about the low FODMAP diet plan and what steps you should follow

The low FODMAP diet doesn’t work for everyone, so if your symptoms don’t improve after a few weeks of avoiding high FODMAP foods, speak to your doctor or dietician. They can give you further advice on other treatments that can help you start to feel more normal again.

But as your diet isn’t the only trigger for IBS, it’s also worth thinking about other possible causes for your symptoms and any changes you could make to your lifestyle. Read about other

self-care tips for IBS
you can try.

Watch this space: low FODMAP and endometriosis

A small study has suggested a low FODMAP diet may also help with

. IBS and endometriosis share many of the same symptoms, such as bloating, diarrhoea and constipation, and it’s thought a low FODMAP diet could help manage the condition. But again, we don’t have enough evidence for this just yet.

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.