Definition

FODMAP is an acronym standing for:

  • Fermentable
  • Oligosaccharides
  • Disaccharides
  • Monosaccharides
  • And
  • Polyols

These are categories of short-chain carbohydrates that the human small intestine absorbs poorly. Instead, they reach the colon where bacteria ferment them, producing hydrogen, methane, and CO₂ — gases that cause distension and discomfort in sensitive individuals.

The five categories

1. Fructans (oligosaccharides — fructose chains)

  • Wheat, rye, barley
  • Onion, garlic, leek
  • Asparagus, artichoke

2. Galacto-oligosaccharides / GOS (oligosaccharides — galactose chains)

  • Beans, lentils, chickpeas
  • Cashews, pistachios

3. Lactose (disaccharide — glucose + galactose)

4. Fructose in excess of glucose (monosaccharide)

  • Apples, pears, mangos, watermelon
  • Honey, high-fructose corn syrup
  • Agave nectar

5. Polyols (sugar alcohols)

  • Mushrooms, cauliflower, snow peas
  • Stone fruits (peaches, plums, cherries)
  • Sugar substitutes ending in “-ol”: sorbitol, mannitol, xylitol, erythritol

Why FODMAPs cause bloating

In most people, FODMAPs ferment in the colon without producing significant symptoms — they’re actually beneficial prebiotic fuel for gut bacteria. The problem arises in people with:

  • IBS (irritable bowel syndrome) — gut hypersensitivity amplifies the perception of normal fermentation
  • SIBO (small intestinal bacterial overgrowth) — fermentation happens in the wrong location, before absorption
  • Functional dyspepsia — slow motility worsens fermentation

For these populations, the same fermentation that’s benign in healthy guts produces bloating, gas, abdominal pain, and altered bowel habits.

What to do

A low-FODMAP diet is a structured three-phase diagnostic protocol:

  1. Elimination (2-6 weeks) — remove all FODMAPs, assess symptom response
  2. Reintroduction (6-8 weeks) — systematically test each category to identify your specific triggers
  3. Personalization — long-term avoidance of only your trigger categories, with re-incorporation of tolerated FODMAPs

For the full walkthrough see our low-FODMAP explained guide.

The protocol has strong evidence (~70-80% improvement in IBS-spectrum bloating) when properly executed. It’s also frequently misused as a permanent restriction — which damages microbiome diversity and can worsen the underlying issue.

Sources

  1. 1.Halmos EP et al. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology, 2014. PMID: 24076059
  2. 2.Gibson PR, Shepherd SJ. Evidence-based dietary management of functional gastrointestinal symptoms: the FODMAP approach. Journal of Gastroenterology and Hepatology, 2010. PMID: 20136989