What's the low-FODMAP diet?

Here's what you should know about the low-FODMAP diet.
Here's what you should know about the low-FODMAP diet.

If you suffer from IBS, you may have come across suggestions to give a low-FODMAP diet a go. But what exactly does it entail? Can it be described as a “diet”? And could it drastically improve your symptoms? We break down the basics.

What is FODMAP?

The abbreviation FODMAP stands for:

  • Fermentable,
  • Oligosaccharides,
  • Disaccharides,
  • Monosaccharides, and
  • Polyols

These are carbohydrates (sugars) found in many common foods. When poorly absorbed, they cause IBS symptoms. Research has found that limiting FODMAPs in your diet could have a favourable effect on those with IBS. In an Australian study, 75% of IBS patients showed improvements in their symptoms on the low-FODMAP diet.

Why do FODMAPs trigger symptoms of IBS?

According to About IBS, the small FODMAP molecules cause an osmotic effect in the small and large intestine – this means that more fluid is attracted to the bowel, which ultimately causes discomfort and bloating. These FODMAPs also ferment rapidly when the colonic microflora produce gas. When gas increases, this additionally causes discomfort and bloating. It also affects how the muscles in the bowel contract, causing increased peristalsis (movement of the digestive tract), which leads to diarrhoea.

Normal digestive systems also respond to the malabsorption of FODMAPs in food, but in people with IBS, the effect of FODMAPs may be amplified because of the following reasons:

  • The muscles of the bowel respond more rapidly, meaning that this could either cause faster or slower movement through the gut, leading to either diarrhoea or constipation.
  • The gut of someone with IBS is hypersensitive to any changes and people with IBS may feel abdominal pain much more quickly than someone without IBS, even though the same process occurs.
  • The type of bacteria also plays a role – they may produce a larger amount of gas, or there may be an overgrowth of gut bacteria (small intestinal bacterial overgrowth, also referred to as SIBO). 

Why the FODMAP diet doesn’t always work

Criticism of a low-FODMAP diet includes that it could be very limiting and cause over-restriction and a lack of crucial nutrition. However, experts agree that the focus should be on “low” FODMAP and not “no” FODMAP.

According to the Harvard Medical School, someone who suffers from IBS and wants to benefit from a low-FODMAP diet should not restrict all foods on the FODMAP list but should only limit problematic foods in a category.

It is also important to understand that the low-FODMAP diet is a process of elimination based on foods which an individual does not respond well to, and not a list of foods that someone with IBS should avoid as a whole.

"In my practice I find some people are not good candidates for an elimination diet, particularly those at risk for eating disorders, those with little control over their food (such as people living in community situations), and those whose diet history reveals that they are already following an instinctively-determined low-FODMAP diet," says Patsy Catsos, a registered dietitian.  

High-FODMAP foods include: Onions, garlic, vegetables, such as asparagus, cauliflower, fresh beetroot, mushrooms, fermented foods, such as sauerkraut, a broad variety of legumes, such as kidney beans and black beans, fruits, such as apples, blueberries, pomegranates, avocado and dates, processed meats and refined starch, such as biscuits and cereals, processed condiments, such as tomato sauce, and dairy products, such as cheese and full-fat milk.

Low-FODMAP foods include: Vegetables, such as carrots, bell peppers, aubergine and leafy greens, fruits, such as grapes, papaya, unripe bananas, strawberries and kiwifruit, unprocessed sources of protein, such as lean beef, chicken and seafood, and grain-free, gluten-free breads and cereals. 

*For a comprehensive list of high- and low-FODMAP foods, see this link.

Important to know

Speak to your doctor or a registered dietitian before diagnosing yourself with IBS.

Always have realistic expectations on the low-FODMAP diet – many people with IBS expect to be symptom-free after avoiding all the foods on the list. It doesn’t work like that.

“Learning more about how your body reacts to FODMAPs can empower you to manage your IBS more effectively,” says Catsos. 

You should also be aware of your fibre intake. One mistake that IBS patients often make is to eliminate all sources of fibre – fibre is crucial for the proper functioning of the digestive system.

Ensure that you get plenty of fibre by including fruits, vegetables, grains, legumes, nuts and seeds from the low-FODMAP list. These fibres are fermented slowly and are less likely to lead to more fluid in the gut, according to the International Foundation for Functional Gastrointestinal Disorders (IFFGD).

The solution is to deliberately increase your intake of fibre from low-FODMAP foods: Eat a wide variety of low-FODMAP fruits and vegetables, low-FODMAP grains and legumes, and small servings of low-FODMAP nuts and seeds.

*Disclaimer: The foods mentioned in this article form part of an extremely condensed list – those who wish to follow a low-FODMAP diet should work in conjunction with their doctors and/or nutritionists. 

Image credit: iStock

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