A dietitian’s guide to the Low FODMAP diet

The low FODMAP diet is one of the most commonly Googled diets in New Zealand and a popular topic on our Ask A Dietitian  hotline.

This evidence-based diet was developed by Australia’s Monash University to help identify possible food triggers of Irritable Bowel Syndrome (IBS) and ease the symptoms.

And it’s no wonder it’s a hot topic, with 1 in 7 people (and even more women) suffering through the debilitating stomach pains and often embarrassing signs of IBS.

So to help answer your low FODMAP queries, we’ve asked Sanitarium dietitian Eliza Baird to share her expert insights on common questions about the low FODMAP diet and bust some of the most common FODMAP myths.

What is the low FODMAP diet?

Science lesson alert: The acronym FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols - try saying that even once fast. These are fermentable carbohydrates that are present in everything from bread to kūmara, avocadoes to apples.

FODMAP is really just a fancy way of categorising foods that can upset your gut. A low-FODMAP diet, under the guidance of a dietitian, encourages you to eliminate certain foods that tend to cause symptoms for people with IBS and then slowly reintroduce them to see what’s causing all those tummy troubles.

What is IBS and why can FODMAPs trigger symptoms?

Irritable Bowel Syndrome (IBS) is a common gut condition with symptoms including reoccurring cramping, bloating, excess wind, and altered bowel habits ranging from constipation to diarrhoea. While there’s no known cause, potential IBS triggers may also include stress, infection and medication – in other words, our typical fast-paced, running-on-empty modern lifestyle.

So, what role do FODMAPs play? These types of carbohydrates are easily fermented by our gut bacteria, and this process produces gas. FODMAPs can also draw water into your gut, causing more cramping and bloating. Depending on your digestive system, the combination of producing gas and drawing water in can lead to constipation, diarrhoea and/or tummy pain.

High FODMAP food swaps

FODMAPs are found in a wide range of foods, however for most foods, there are low FODMAP alternatives. Here are some common foods that are high and low in FODMAPs:

 High FODMAP foodsLow FODMAP foods
VegetablesAsparagus, beetroot, kūmara, mushroom, onion, garlic, artichoke, green peas, leekCarrots, green beans, bok choy, capsicum, cucumber, lettuce, spinach, silverbeet, tomato, courgette, potato
FruitsApple, apricot, nectarine, mango, pear, peach, dried fruitMandarin, blueberries (max ¼ cup), kiwifruit, green banana, lemon, lime, orange, passionfruit, and pineapple
Milk and dairyCow’s milk, yoghurt, soft cheeses, cream, custard, ice-cream, soy milk made from soy beanPlant-based milks e.g. almond milk, soy milk made from soy protein isolate, lactose-free milk, lactose-free yoghurt, hard cheese
ProteinLegumes (baked beans, kidney beans, chickpeas, lentils etc), some processed and marinated meats, cashew and pistachio nuts.Firm tofu, eggs, tempeh, almonds (limit 10 per serve), macadamia nuts, peanuts, walnuts, pumpkin seeds, sunflower seeds. If eating meat, plain meat, poultry, seafood and fish
GrainsWheat, rye, barley and foods made from these grains. Most breads, cereals, pasta, noodles and crackersGluten free bread, sour-dough spelt bread, oats, gluten free pasta, rice, quinoa, amaranth, millet, polenta, sorghum, buckwheat
OtherHoney, artificial sweeteners, chewing gum, foods containing inulin or chicory rootDark chocolate, maple syrup, popcorn, brown rice crackers topped with peanut butter

Note: this is not a complete list and should not replace advice from your dietitian/ health care provider.

In addition, portion size for some foods can change whether they’re low or high FODMAP. For example, a 75g serve of eggplant is low FODMAP, while 260g of eggplant is high FODMAP.

If you have been diagnosed with IBS, speak to your health care provider before trying the low FODMAP diet. It can be tricky to navigate without professional support, especially given that you’re eliminating foods, you will want to ensure you’re still getting adequate nutrients.

It’s important to know, w hile a low FODMAP diet can help to diagnose the key food triggers for most IBS patients, Monash University reports that 1 in 4 will need to try alternative IBS treatments. Want to know more? You can find a Monash FODMAP trained dietitian in your area here.

What should I do when eating out on a low FODMAP diet?

Try looking at the menu online before going out and spend some time identifying the best option for you. You may be able to ask for your worst trigger foods to be taken out of your meal. Also, calling the restaurant before you go will help with specialised meal requests and you can ask which dishes do not contain onion and garlic before ordering.

Avoid very rich dishes with lots of sauce or ones made with stock, for example curry or risotto, as they often include onion and garlic. Also dips, sauces, and dressings often contain onion and garlic, so ask for these to be served separately.


MYTH 1: Everyone should avoid high FODMAP foods

What do apples, apricots, grapes, mangoes and pears have in common apart from being delicious fruits? Or asparagus, beetroot, butternut squash, snow peas and mushrooms?

These fruits and vegetables are high FODMAP and a great example that many high FODMAP foods are really healthy. They provide important vitamins and nutrients such as prebiotic fibre, which is good for gut health in most people, but can trigger symptoms in some people with IBS.

You should only avoid high FODMAP foods if they cause you to experience IBS symptoms and you’ve been recommended to by your dietitian or a health professional.

MYTH 2: Low FODMAP is also low fibre

One doesn’t equal the other. In fact, if you are following a low FODMAP diet, you’ll need be on the hunt for low FODMAP foods that contain fibre and there are plenty. Incorporating them into your diet will help to keep you regular, especially if you’re prone to constipation.

Some examples of low FODMAP, fibre-containing foods include oats, sorghum cereal, green kiwi fruit, quinoa, brown rice, wheat/rye/barley-free breads, pumpkin seeds and walnuts.