What is a low FODMAP diet?

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. These are the chemical names of 5 naturally occurring sugars that are not well absorbed by your small intestine.

In some people with irritable bowel syndrome (IBS), these sugars can trigger symptoms, such as:

• diarrhoea
• flatulence (farting)
• abdominal (tummy) pain
• bloating
• constipation

These symptoms can affect your life, make you feel uncomfortable and cause embarrassment.

The low FODMAP diet was developed by researchers at Monash University in Victoria, Australia. The researchers identified which foods are low and high in FODMAPs.

People with symptoms of IBS may find it helpful to:

• limit the amounts of high FODMAP foods they eat
• increase the amount of low FODMAP foods they eat

Which foods are high in FODMAPs?

Many foods contain FODMAPs. Some of these foods are:

• garlic, onions and leeks
• apples, pears, watermelon and stone fruits
• green peas, chickpeas and lentils
• cabbage, avocados, mushrooms and cauliflower
• dairy products such as milk, yoghurt and custard
• wheat, barley and rye
• cashews and pistachios

Low FODMAP foods include:

• green capsicum, green beans, carrots, cucumbers and zucchini
• oranges, kiwi fruit, pineapple and strawberries
• eggs
• plain cooked meat
• oats
• peanuts, macadamias and walnuts

For a complete list of high and low FODMAP foods, visit the Monash University FODMAP website. You can use the Monash FODMAP app.

What if I want to start a low FODMAP diet?

If you are considering a low FODMAP diet, you should consult a dietitian. They can advise you on:

• which foods to eat
• which foods to avoid
• reintroducing certain foods back into your diet so you can figure out which foods trigger your IBS

How to follow a low FODMAP diet

A low FODMAP diet is not a lifetime diet because it's not nutritionally complete. It's usually recommended for 2 to 6 weeks. This can help you better understand your IBS food triggers. It can also help relieve your symptoms within 4 weeks.

A low FODMAP diet has 3 stages, and should be started with the help of a dietitian.

Stage 1

In the first stage, you temporarily reduce foods that contain FODMAPs. This helps you to work out if your symptoms are triggered by these sugars.

Stage 2

If your symptoms have improved after stage 1, you can start to reintroduce one FODMAP food group at a time. This is called a 'FODMAP challenge'.

Each challenge lasts around 3 days, during which you can record any IBS symptoms you have.

FODMAP challenges will help figure out which foods trigger your symptoms.

Stage 3

In the last stage, you learn how much of these foods you can eat before your symptoms appear. Some people find that they only need to avoid some high FODMAP foods, not all of them. You can then follow a diet that:

• includes FODMAP foods you can tolerate
• restricts the foods that trigger your IBS symptoms

This way of eating can be followed long-term. It can help you control your IBS symptoms.

If your symptoms have not improved on the FODMAP diet, you should see your doctor for advice on other therapies.

Possible side effects of low FODMAP diets

While you're on the first stage of a FODMAP diet, your diet may be lacking certain nutrients. These include:

• calcium
• iron
• dietary fibre
• vitamins
• protein

Eating some FODMAP foods is also thought to temporarily change the important microbes in your gut

Because of this, it's important that you see a dietitian. They can suggest low FODMAP alternatives to ensure you still get adequate nutrients. You may also need to take vitamin and mineral supplements in the short term.

Will a low FODMAP diet work for me?

Before you begin a low FODMAP diet, you should see your doctor. They can help make sure that what you have is IBS and not another condition such as:

• inflammatory bowel disease
• coeliac disease
• endometriosis
• bowel cancer

Sometimes, IBS symptoms can be triggered by things other than FODMAPs in your diet, such as:

• high fat foods
• alcohol
• caffeine
• stress

Your doctor and dietitian can help you identify if these other things are an issue for you.

If you follow the low FODMAP diet and your symptoms don't improve, speak to your dietitian. They can suggest other therapies, including stress reduction and fibre supplements.

Resources and support

Monash University has information on low FODMAP diets, including:

• FODMAPs and irritable bowel syndrome
• starting the FODMAP diet
• FODMAP diet app

Dietitians Australia has information on IBS and a tool to find a dietitian.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.