Food intolerance and FODMAPs

FODMAP

Also called: FODMAPs

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. They are short-chain carbohydrates that some people's guts struggle to absorb. When they reach the lower gut undigested, bacteria ferment them, producing gas and pulling water in. The result is bloating, wind, and loose stools in those who react.

What FODMAPs actually are

FODMAPs are not bad foods. They are a group of carbohydrates that share one trait: small molecule size and rapid fermentation by gut bacteria. The acronym was coined in 2005 by researchers at Monash University in Melbourne, who showed that restricting these foods helps roughly three in four people with irritable bowel syndrome.

The four groups

  • Oligosaccharides: fructans (in wheat, onion, garlic) and galacto-oligosaccharides (in lentils, chickpeas, baked beans).
  • Disaccharides: lactose (in cow's milk, soft cheese, yoghurt). Affects people with lactase enzyme deficiency.
  • Monosaccharides: excess fructose, where fructose levels in a food sit above the glucose levels (in apples, pears, honey, high-fructose corn syrup).
  • Polyols: sorbitol, mannitol and xylitol (in stone fruit, mushrooms, sugar-free chewing gum).

How to know if FODMAPs affect you

The clearest test is the Monash low-FODMAP diet, a structured three-phase protocol of strict elimination, reintroduction, and personalisation. NICE recommends it for IBS that has not responded to first-line dietary changes. The diet typically takes six to eight weeks under the guidance of a registered dietitian.

It is not meant as a forever diet. Long-term restriction reduces fibre diversity and can shrink beneficial gut bacteria. The point of phase two is to reintroduce each FODMAP group systematically and identify the specific subgroups that trigger you.

Who should not try low-FODMAP without guidance

  • Anyone with a history of disordered eating or restrictive eating.
  • Children and adolescents (the diet is studied in adults).
  • Pregnant women.
  • People with active inflammatory bowel disease, where the priority is settling inflammation first.

What FODMAP is not

FODMAPs are not the same as gluten. Gluten is a protein. Fructans, the FODMAP often blamed for wheat-related symptoms, are a carbohydrate. Most people who feel better on a gluten-free diet are responding to the fructans in wheat, not the gluten itself, unless they have coeliac disease.

Common questions

Is low-FODMAP the same as gluten-free?
No. Wheat is high in fructans, a FODMAP, so reducing wheat helps both coeliac and IBS symptoms. But gluten-free products can still contain high-FODMAP ingredients like onion powder or honey, and many low-FODMAP foods contain gluten.
How long does it take to see results?
Most people who respond notice changes within two to three weeks of strict elimination. If symptoms have not improved after six weeks, the issue is unlikely to be FODMAPs and reintroduction should begin so the gut microbiome is not unnecessarily restricted.
Is it safe to stay low-FODMAP forever?
Long-term restriction is not advised. The diet limits prebiotic fibres that feed beneficial gut bacteria, and microbiome diversity drops within weeks. The reintroduction phase is essential for identifying personal triggers.
Who developed the FODMAP concept?
Sue Shepherd and Peter Gibson at Monash University in Melbourne defined and named FODMAPs in 2005. Monash maintains the world's reference database of FODMAP content in foods and certifies products as low-FODMAP.

Sources