May 07, 2024

A low-FODMAP diet is sometimes recommended for people suffering Irritable Bowel Syndrome (IBS) or dealing with gut issues such as bloating, gas or abdominal pain. We asked naturopath and medical herbalist Jane McClurg  what you need to know about FODMAPs, when it’s right to eliminate them from your diet and how to go about it safely.

What are FODMAPs?

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols - basically it covers several groups of foods that the small intestine can have difficulty digesting which means that eating them can cause gut issues for some people. In an upcoming blog we will have a full food table covering off FODMAP-friendly foods but here is a general list of foods to avoid if you decide to try a low-FODMAP diet.

Oligosaccharides: wheat, rye, nuts, legumes, artichokes, garlic, and onion

Disaccharides: lactose-containing products such as milk, yogurt, soft cheese, ice cream, buttermilk, condensed milk, and whipped cream

Monosaccharides: fructose-containing foods, including fruits such as apples, pears, watermelon, and mango and sweeteners such as honey, agave nectar, and high fructose corn syrup

Polyols: mannitol and sorbitol in apples, pears, cauliflower, stone fruits, mushrooms, and snow peas, as well as xylitol and isomalt in low calorie sweeteners, such as those in sugar-free gum and mints.

What are the signs your gut might not tolerate high-FODMAP foods?

Bloating, gas, abdominal pain and food intolerances are the main signs you’re not tolerating FODMAPs because these foods may be fermenting in your small intestine or large intestine. Altered bowel habits such as diarrhoea, constipation or switching between both or having that feeling of not a complete evacuation can be signs of IBS or SIBO (Small Intestinal Bacterial Overgrowth.)

As FODMAPs move through the gut they attract water and when they reach the large intestine, the bacteria there ferments the FODMAPs, producing gas, distension and pain.

Research has shown more than 70 per cent of people with IBS have SIBO, so these FODMAP foods are being fermented in the small intestine by bacteria that shouldn’t be there.

If you experience bloating with 60 to 90 minutes of eating and you feel bloated above the belly button, then it’s possible you have SIBO. I highly recommend getting tested for SIBO and clear this up first as it can resolve so many digestive issues for people, and they are even able to eat most FODMAP foods again.

If you test negative for SIBO, then the large intestine and its microbiome needs some TLC. Often it can be both areas that need some gut healing.

There are many conditions with symptoms that are similar to IBS, such as coeliac disease, inflammatory bowel disease, endometriosis and bowel cancer. You should not self-diagnose yourself with IBS. It’s always best to talk to your doctor and naturopath and have a great team to support you.

What are the benefits of a low-FODMAP diet?

It can reduce symptoms such as bloating, gas, pain and constipation and diarrhoea issues. However, limiting FODMAP foods should always be a for a short time as these foods are really beneficial for our gut health. So eliminating FODMAPs is best done as a therapeutic diet while you take steps to heal your gut. Working with a practitioner is always the best way to go. 

What are the steps you should take to trial a low-FODMAP diet?

If you are suffering with bloating, gas, pain and have been diagnosed by a health professional as having IBS, I would recommend testing for SIBO first and working with a practitioner as you start to eliminate FODMAP foods. You want to make sure that you are not just cutting out foods willy nilly!

Track your food and symptoms for a week in a food diary to see which foods trigger your symptoms and start with cutting those out first (not forever!).

After four to six weeks of elimination, and in tandem with some gut healing strategies, then you can move into the re-introduction phase (possibly another four to six weeks). This is where you re-introduce one food at a time and watch for any symptoms. I recommend waiting four to five days between introducing new foods.

Maintain your food diary while you are reintroducing foods – it will help you accurately assess whether you can tolerate FODMAP foods and in what quantity. You might be able to eat onions once or twice a week but find that more often than that causes your gut to react.

Everyone is different when it comes to which high-FODMAP foods affect them, and eventually you will come up with a personalised plan of what you can eat without upsetting your gut.

Ideally, a good diet is diverse, but the reality is there might be some foods you can’t tolerate.

Jane is a New Zealand based degree-qualified naturopath and medical herbalist.