Your complete beginners guide to going low-FODMAP

Author: Katrina Pace - MSc, New Zealand Registered Dietitian

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Scientific studies have shown that a low-FODMAP diet can significantly relieve irritable bowel syndrome (IBS) symptoms for many sufferers.

This complete guide to the low-FODMAP diet is intended as a resource only. A low-FODMAP diet is used to help symptoms of certain gastrointestinal conditions and should only ever be undertaken with the supervision of your doctor or relevantly-qualified dietitian. The strict elimination phase of the diet is intended to be followed for two to six weeks only, followed by long-term transition onto a modified diet that lets you return to enjoying high-FODMAP foods you can tolerate. If you prefer having this complete guide in a print booklet form you can purchase it, details here. Very handy if you want to refer to it often.

What is IBS?

Irritable bowel syndrome is a ‘functional gastrointestinal disorder’. This means it causes changes in the function of the gut but doesn’t have any features such as ulcers, inflammation, thickening of digestive tissues, lumps and bumps or abnormal blood tests – all of which would indicate a different condition.

The diagnosis of IBS relies upon the types of symptoms experienced and their context, such as how long they’ve been experienced and when they occur.

The symptoms of IBS can be similar to other conditions, such as coeliac disease, inflammatory bowel disease, ulcers, ovarian cancer, bowel cancer and endometriosis. Before starting any treatment for IBS it’s critical to see your doctor and have these conditions ruled out.

Symptoms of IBS

If you have IBS you can experience a broad range of symptoms including abdominal pain and discomfort, bloating, changes in bowel habits (constipation or diarrhoea), heartburn, and nausea. Other symptoms can include excessive wind, unsatisfied defecation (incomplete emptying), passage of slimy mucus into the toilet bowl, a noisy abdomen (the noises are called borborygmi) and pain in the rectum.

Tiredness is also common, and its severity usually depends on that of the bowel symptoms. Severe muscle aches and pains (called fibromyalgia) occur in some people, while others experience an ‘irritable bladder’ (urinary frequency and urgency).

For more on IBS you might be interested in:

Food triggers for IBS

People with IBS often know that certain foods will trigger their symptoms. It has been shown that dietary change is the major way in which people with IBS attempt to help themselves.

Basic steps to help improve symptoms include avoiding poor eating habits, such as stress-filled meals or always eating on the run, or dietary extremes such as too many cups of coffee each day, too little water, eating too little fibre or suddenly changing to a diet full of fibre. But, until the low-FODMAP diet, there was minimal scientific evidence that specific dietary changes helped people with IBS.

Check out our seven-day plans for healthy eating to make sure you’re starting with good eating habits:

What are FODMAPs?

FODMAPs are part of the food group, carbohydrates (starchy food). They’re the favourite food for bacteria that live naturally in the digestive system.

The word ‘FODMAP’ stands for:

Fermentable: Eaten by bacteria to produce gases and heat

Oligosaccharides: Complex carbohydrates (fibres)

Disaccharides: Milk sugars

Monosaccharide: Simple sugars

And Polyols: Another food bacteria like

Foods high in FODMAP carbohydrates can cause the bowel to swell by drawing in more fluid and producing excess gas when they are fermented by the bacteria found in the digestive system. This causes the symptoms of bloating, abdominal pain and change in bowel habits.

Is a low-FODMAP diet suitable for you?

Dietitians with expertise in gastrointestinal nutrition and many doctors now recommend a low-FODMAP diet as a cornerstone of their treatment for people with IBS. Two recent studies found 72 to 86 per cent of IBS patients had fewer symptoms on a low-FODMAP diet. One study also provided more evidence of the effect on gut bacteria, with the low-FODMAP diet increasing the richness and diversity of one type of bacteria. The other study, which followed people over 18 months, found most had successfully reintroduced FODMAP foods.

You might benefit from a low-FODMAP diet if:

You’ve been diagnosed with IBS by your doctor
You have symptoms of IBS and no other medical cause has been found
You’ve been diagnosed with bacterial overgrowth (SIBO).

Always make sure you’ve seen your doctor before starting a low-FODMAP diet. Why? The low-FODMAP diet is very low in gluten. As symptoms of IBS are very similar to coeliac disease (an autoimmune condition causing a gluten allergy), it’s important to get tested for coeliac disease before reducing gluten in your diet. There also may be other reasons for your symptoms that your doctor needs to check for.

What can I expect from a low-FODMAP diet?

There are three stages to the low-FODMAP diet: elimination, food challenges and food reintroduction.

Starting the low-FODMAP diet, identifying your food triggers and then reintroducing safe foods takes around 12 weeks.

The low-FODMAP diet is not a diet for life. The aim is to get back to a healthy, balanced Mediterranean-style diet, which has been shown to be good for all aspects of health including healthy gut bacteria.

Weeks 1-4 Elimination

The aim of the elimination stage of the diet is to reduce the total number of all FODMAPs in the diet and give your digestive system some rest.

By the end of this stage you should know whether FODMAPs are the trigger group of foods for your symptoms. Seventy-five to 80 per cent of people following a low-FODMAP diet for IBS find they have at least 70 per cent improvement in their symptoms after the elimination stage.

Foods to avoid in the elimination stage

*This list needs reviewing and updating by a FODMAP diet expert

Stage 1: Elimination low-FODMAP menu plan

Breakfast

Porridge oats made with water and lactose-free milk or milk substitute. Top with cinnamon and brown sugar, banana or blueberries. Try: Almond and mixed seed porridge
Make your own muesli with oats, seeds, nuts and gluten-free grains. Serve with lactose-free yoghurt or milk, blueberries and kiwifruit. Try: Fruit-free muesli
Gluten/wheat-free bread, toasted, with margarine and marmalade
Omelette or eggs and gluten/wheat-free toast or bread. Try: Breakfast baskets

Lunch

Sandwich made with gluten/wheat-free bread. Try fillings such as ham, lettuce, tomato, tuna mayonnaise, hard cheese, small amount of avocado and smoked chicken.
Homemade low-FODMAP carrot, buttercup pumpkin or other soup with gluten/wheat-free bread. Try: Low-FODMAP spicy lentil soup
Frittata or Spanish omelette. Try: Low-FODMAP savoury vegetable frittata
Baked potato with mince, hard cheese or tuna mayonnaise
Sushi or sushi bowls. Try: Quinoa, smoked salmon and shredded vegetable sushi rolls and Seared salmon sushi bowls
Leftover main meals

Dinner

Chicken stir fry, served with rice noodles or rice.
Gluten/wheat-free pizza base with tomato, olives, cheese, chicken, sausage or ham topping or a low-FODMAP calzone.
Steak, potato and low-FODMAP vegetables. Try: Low-FODMAP seared steak with maple mustard sauce and quinoa salad
Baked/poached/grilled fish with rice, potato, fries or small amount of kumara and low-FODMAP vegetables. Try: Chia, almond and herb-crusted fish
Low-FODMAP chicken and veggie bake tray with pesto.
Gluten/wheat-free pasta or spaghetti with minced beef in a tomato sauce

Snacks

Bliss balls – but check the ingredients and number of serves suitable first
Fresh fruit: kiwifruit, blueberries, strawberries or banana
Rice cakes with peanut butter or cheese and marmite
Plain rice crackers
Sunflower, peanut and almond mix
Gluten/wheat free baking such as lemon and poppy seed loaf
Carrots, cucumber (peeled) and cherry tomatoes with dip
Hard-boiled egg

For more low-FODMAP meal ideas check our low-FODMAP recipe collection.

Stage 1: Elimination FAQ

How much fruit can I eat at a time?

You should eat no more than one serve of ‘suitable’ fruit per meal or sitting. One serve is usually one metric cup of cut-up fruit, or one whole piece of fruit, such as one orange or banana. Try to have 2-3 serves of fruit each day, spread throughout the day.

How do I avoid FODMAPs if I’m a vegetarian or vegan?

Vegetarians often eat a lot of legumes as an important source of protein. However, these contain FODMAPs. As there is a risk that your vegetarian or vegan diet will become nutritionally inadequate if you cut out legumes, it’s advisable to see a dietitian to tailor the diet for you. The best approach will depend on your individual tolerance. Good news though, firm tofu is low in FODMAPs, so can be included as a protein source.

I’ve followed the low-FODMAP eating plan for four weeks and I feel no different. What do I do?

About three quarters of people will have about 75 per cent or more improvement in their symptoms within four weeks of being on a low-FODMAP eating plan. However, some people need a bit longer. Sometimes this may be if you have more severe symptoms, your symptoms have been going on for a very long time (decades rather than years), or high-FODMAP foods have been creeping into your diet.

There may be other food intolerances or food triggers (or non-food triggers) that need to be looked at. It’s time to book an appointment with a specialist dietitian to get an individual opinion.

Weeks 5-12: Food challenges

So far, you’ve been avoiding all FODMAP food groups. Now it’s time to test the individual FODMAP groups. There might be some you’re not having a reaction to.

Many foods contain one or more types of FODMAP. It is really important to make sure that only one group of FODMAP foods is tested at one time.

We need to check one food that contains only sorbitol (and no other FODMAPs), one food that contains only mannitol (and no other FODMAPs), one food that only contains fructose (and no other FODMAPs), and so on.

How to do the challenges

Keep to a low-FODMAP (stage 1) diet throughout the challenges, apart from the specific challenge food.
Wait until you have no symptoms for at least three days before starting a challenge.
If you’re symptom free for at least three days, try to have one challenge each week.
If you’re given a choice of challenge foods, stick to the same food for each day of the challenge.
Keep your symptom diary throughout the challenges.
Each challenge is for three days but stop the challenge as soon as you notice symptoms.

Challenge day 1

Have one serving of the challenge food during the day. If you’ve got symptoms, stop. If you’re feeling fine continue to day 2.

Challenge day 2

Have two servings of the challenge food during the day If you’ve got symptoms, stop. If you’re feeling fine continue to day 3.

Challenge day 3

Have three servings of the challenge food during the day. If you’ve got symptoms, stop. If you’re feeling fine then this is unlikely to be a trigger food group.

Make a note in your symptom diary of which day (if any) you had a reaction on.

Download your weekly challenges here

Stage 2: Challenges FAQs

FODMAP groups

Oligos – Fructan Oligosaccharide

Galacto oligo saccharides (GOS)

Oligosaccharide

Lactose Disaccharide

Fructose Monosaccharide

Mannitol Polyol

Sorbitol Polyol

Will I get symptoms during the prescribed food challenge?

Yes. But the food challenges give you some really important and valuable information such as what foods you are actually reacting to, whether you get different reactions from different FODMAP groups and how much you can eat before you get a reaction.

When is the best time to do the prescribed food challenge?

The good thing about the food challenge is that you can start them on a Friday afternoon and be done by Sunday night. This means that, hopefully, there will be as little impact on your school or work life as possible. Try to choose a time when you don’t have any busy or social activities scheduled. Make sure you are feeling well in general. Don’t start if you feel a cold coming on.

Why are there three fructan challenges?

We know a lot about FODMAP foods, but there are still some things to find out. One is that some people are okay with bread but not with onion or garlic. Or, some are okay with onion but not garlic. There is obviously something else other than fructans that triggers symptoms.

If I don’t react to the food, can I include it in my diet?

Sorry, but not at this stage. It is important to continue eating the low-FODMAP diet plan in stage 2 while you are doing all the challenges. The only new food should be the one you eat for the challenge.

I reacted to EVERY prescribed food challenge

There may be other food intolerances or food triggers (or non-food triggers) that need to be looked at. It’s time to book an appointment with a specialist dietitian to get an individual opinion.

Anxiety-reducing tips

It is likely that at some point during your FODMAP challenges you will experience symptoms. The fear of having a FODMAP reaction at work can be a major hurdle for many people. You can do these three-day food challenges over the weekend to keep the impact on work to a minimum.

Once you have started your challenges try to relax. Stress by itself can trigger IBS symptoms. If you can, try to be mindful and relaxed, and let your digestive system process the FODMAP without additional pressure.

Also, remember that everyone’s digestive system can get a little bit gurgly or noisy at times, and it is completely normal to experience a small amount of gas or mild bloating. Any symptoms that cause pain or more than mild discomfort indicate a FODMAP reaction. Try to focus on the positive. If you pass the challenge, you get to add more foods back into your diet.

Weeks 13 onwards: Food reintroduction

Now you’ve completed the food challenges you should have a list of which FODMAP groups you reacted to and you’re ready to start reintroducing those.

You also know which FODMAP trigger groups give which of your symptoms. Knowing which symptoms come from which FODMAP group can help you identify what the trigger was if you have an unexpected reaction.

Now it’s time to start reintroducing the foods you didn’t react to.

You can download the Monash Low FODMAP Diet app to help you identify the FODMAP content of foods.

Using the Monash Low FODMAP Diet app with your food challenge results

You can use the filter feature to tailor the results from the app.

If you had a reaction on day 1 you’re sensitive to this FODMAP group, so avoid all the red and orange coded foods on the Monash low FODMAP app. Choose only green coded foods.

If you had a reaction on day 2 you should avoid all the red coded foods, but may tolerate an occasional (once a week) orange coded food. Choose mainly green coded foods.

If you had a reaction on day 3 you should may tolerate the occasional (once a week) red food, or orange coded foods once or twice a week. Choose mostly green coded foods.

If you had no reaction you can eat all the red and orange coded foods frequently.

Tips for reintroducing safe foods into your diet

Spend an hour on the app to check out the foods you can reintroduce
Slowly reintroduce safe foods. Remember that suddenly increasing fibre and pulses can also cause digestive symptoms.

Related links

Going forward

As your digestion heals, so your tolerance of FODMAP foods should improve. It’s worth re-challenging your FODMAP triggers every 3-4 months. You may find your tolerance gradually improves over time. This guide has a full print ready version available for purchase, details here.

Stress can also be a trigger for IBS. Healthy Food Guide editor, Jenny de Montalk, shares some tips for how to cope with day to day stress.

Exercise also plays a part in reducing stress.

Avoiding your individual low-FODMAP triggers while following a balanced Mediterranean-style diet will help keep you healthy. Here’s how to do it.