The low-FODMAP diet for IBS

Senior Specialist Dietitian at Bupa Cromwell Hospital
29 March 2018

If you have irritable bowel syndrome (IBS) or another disorder affecting your gut, the low-FODMAP diet could help with your symptoms. But it’s definitely not a do-it-yourself diet – getting guidance from a suitably qualified dietitian is essential. If they do suggest following a low-FODMAP diet, you’ll need to do this carefully to ensure it works well, and meets your nutritional needs.

The low-FODMAP diet is broadly about temporarily limiting certain carbohydrates in your diet. Here, I explain more about what it involves, and what you should do before considering it.

Image showing some garden vegetables on a bench

Living with IBS

IBS symptoms – such as tummy pain, bloating, constipation and diarrhoea – can make everyday life a misery. Many people with IBS notice that these symptoms get worse after eating.

Fortunately, there’s a lot you can do to manage IBS. Reducing stress by relaxing more, and staying physically active, can be really helpful. Adjusting your diet can also make a big difference.

Before changing your diet, it’s important to get expert advice based on your diagnosis. Some of the symptoms of IBS can overlap with other gut problems, including coeliac disease or inflammatory bowel disease, which is why it’s important to rule these out. You really need to know your diagnosis and get tailored advice before starting down a particular diet path.

What to do first

The low-FODMAP diet can be effective in reducing IBS symptoms – but it’s not the place to start. Firstly, you have to get the basics right. This means ensuring you already have a generally healthy, balanced diet, and eat three regular meals each day. Then, it’s time to look at your intake of known triggers for IBS symptoms. These could include excessive consumption of alcohol, caffeinated or fizzy drinks, or spicy and fatty foods. It's also important to drink at least eight cups of fluid per day, especially water or other non-caffeinated drinks – for example herbal teas.

If symptoms continue, you could consider restricting milk and dairy foods, or the amount and type of fibre you eat. You may find it worth limiting fresh fruit to three portions per day (one portion is 80 grams).

If you’re still having trouble after these changes, it may be worth considering a low-FODMAP diet.

Working with your dietitian

It’s so important to work with a dietitian who’s trained in the details of the low-FODMAP diet. There are a few reasons for this. The low-FODMAP diet is complex. Because it removes so many foods from your daily intake, there’s a risk you’ll miss out on important nutrients or not stick with the diet. But, the good news is that it’s not a diet for life: you only follow it for six to eight weeks.

You will usually have an initial one-to-one education session, to understand more about the concept behind the diet, and receive tailored advice. Your dietitian will explain how FODMAPs can trigger symptoms. They might give you resources, such as a fact-sheet, about suitable low-FODMAP alternative foods that are available.

What does FODMAP stand for?

Fermentable, Oligo/Di/Mono-saccharides and Polyols (FODMAPs). These are all types of carbohydrates that are poorly absorbed in the small intestine. Here are some more details about what each of those words mean.

  • Fermentable (meaning that gut bacteria break down the nutrients, producing gas)
  • Oligosaccharides (complex carbohydrates)
  • Disaccharides (double-unit sugars)
  • Monosaccharides (single-unit sugars)
  • Polyols (sugars found in some fruits and vegetables, and in artificial sweeteners)

How the low-FODMAP diet might work

The low-FODMAP diet is thought to work by reducing a process called fermentation in the gut. Fermentation happens when naturally-occurring gut bacteria break down certain foods, and produce gases such as carbon dioxide, hydrogen and methane as by-products. In people who are susceptible, this fermentation process can trigger troublesome gut symptoms.

There’s still some debate about whether the low-FODMAP diet has been thoroughly proven. However, some evidence suggests that the low-FODMAP diet can help people with IBS. For example, in one UK study, around seven in every ten people on the low-FODMAP diet said they were satisfied with the improvements to their symptoms. In the same study, only about half of those following conventional IBS dietary advice were satisfied with the improvement in their symptoms.

High-FODMAP foods

Here are some of the foods that are avoided on a low-FODMAP diet. Please talk to your dietitian before eliminating these foods from your diet:

  • wheat
  • rye
  • onions
  • garlic
  • pulses (for example, beans and lentils)
  • milk and dairy foods
  • certain fruits, including apples and pears
  • certain vegetables
  • honey, plus some other natural and artificial sweeteners

The low-FODMAP diet is not for everyone, but it helps to remember that this is just one of many choices that can help ease IBS symptoms. Your initial education session with your dietitian is of utmost importance if the low FODMAP diet is to succeed. If you’re struggling with symptoms, please do talk to a registered dietitian with experience in this area. You might find it’s one of the best things you’ve ever done for yourself.




Do you know how healthy you truly are? Bupa health assessments give you a clear overview of your health. You’ll receive a personalised lifestyle action plan with health goals to reach for a healthier, happier you.

Maya Aboukhater
Senior Specialist Dietitian at Bupa Cromwell Hospital

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