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What is FODMAP and what is the FODMAP diet? How does it work and - why you should or should not follow it?

You may have heard about the FODMAP diet from friends or read about it online.


What exactly is FODMAP?


What is the FODMAP diet?


What is FODMAP?

FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols.


In simple terms, they are carbohydrates that are poorly absorbed in the small intestine and are fermented in the large intestine, for example:

  1. Oligosaccharides (fructans and galactans):
    • Wheat (bread, pasta, cereals, crackers…).
    • Onions (white, red, etc., onions, onion powder…).
    • Garlic (fresh garlic, garlic powder…).
    • Legumes (lentils, chickpeas, beans…).
    • Artichokes (artichokes, Jerusalem artichokes…).
  1. Disaccharides (lactose):
    • Milk (cow’s milk, goat’s milk, sheep’s milk…).
    • Cheese (soft cheeses such as ricotta, cottage cheese…).
    • Yoghurt (yoghurt, Greek yoghurt…).
    • Milk-based ice-cream.
    • Cream (sweet and sour cream).
  1. Monosaccharides (excess fructose*):
    • Honey.
    • Apples (fresh apples, apple juice, apple purees…).
    • Pears (fresh pears, pear juice, purees…).
    • Mangoes.
    • Watermelons.
  1. Polyols or sugar alcohols (sorbitol, xylitol, mannitol).
    • Stone fruit (plums, cherries, apricots…).
    • Sweeteners (sorbitol, mannitol, xylitol).
    • Cauliflower.
    • Mushrooms.
    • Avocados.

Most FODMAPs naturally occur in food and our diet, but polyols may be artificially added to industrially produced foods and beverages.

FODMAPs can cause digestive discomfort in some people. Reasons include hypersensitivity to abdominal distension or a tendency to excessive water retention and gas production and accumulation, but FODMAPs do not cause intestinal inflammation.

Naturally occurring FODMAPs may help some people avoid digestive discomfort by causing beneficial changes in the gut microflora.

Avoiding all FODMAPs for a long time may adversely affect the gut microflora and metabolome.


Our response to FODMAPs is highly individual – some people tolerate certain FODMAPs better than others. People with irritable bowel syndrome (IBS) or other functional gastrointestinal disorders often experience more severe and unpleasant symptoms.


* Excess fructose means there is more fructose in the food than glucose. This imbalance can cause problems because fructose is absorbed more efficiently in the small intestine if glucose is also present. If there is more fructose than glucose, the absorption process can become inefficient – the fructose passes into the large intestine where it is fermented by bacteria, which in turn can cause symptoms such as bloating, gas and diarrhoea, especially in people with fructose intolerance (malabsorption).


What happens when we eat FODMAP-rich foods?

When we consume FODMAP-rich foods, several physiological processes occur in our body:

  1. Intake and digestion in the stomach:
    1. Initial digestion – the food is chewed and mixed with saliva, which contains enzymes that start the digestive process.
    2. The food passes into the stomach where it mixes with gastric juices. Proteins and fats are mainly broken down in the stomach, while carbohydrates, including FODMAPs, remain largely intact.
  1. The partially digested food enters the small intestine and mixes with digestive enzymes. Some carbohydrates are broken down and absorbed, but FODMAPs often defy digestion and continue to move through the digestive tract.
  1. Osmotic effect – FODMAPs produce the osmotic effect by drawing water into the small intestine (water moves from the surrounding tissues and bloodstream into the intestinal lumen where the FODMAP is located). This can increase the water content of the intestine, potentially causing diarrhoea or watery stools.
  1. Undigested FODMAPs pass into the large intestine and are rapidly fermented by intestinal bacteria. This fermentation process produces gases such as hydrogen, methane and carbon dioxide. The accumulation of these gases can cause bloating, abdominal pain and flatulence.

These processes occur in everyone, with or without irritable bowel syndrome (IBS). The difference is that people with IBS may have problems with motility (the speed at which contents move through the gut) and/or have highly sensitive gut walls. The extra water and gas in the intestine cause the intestinal walls to stretch and expand, resulting in IBS-specific symptoms such as abdominal pain, bloating, feeling stuffed and other bowel problems (diarrhoea, constipation, etc.).


What is the FODMAP diet?

The FODMAP diet is generally understood as a low-FODMAP diet.


It is more correctly described as a diagnostic method rather than a diet, as it is designed to help people with irritable bowel syndrome (IBS) and/or certain bacterial overgrowth in the small intestine (SIBO) find out which foods cause and which reduce the symptoms.

A low FODMAP diet is a temporary eating plan that is very restrictive because many foods are excluded.


Phases of the FODMAP diet:

  1. The elimination phase, during which all foods high in FODMAPs must be strictly avoided for about 4-6 weeks.
  1. Introduction phase. Once symptoms have subsided, foods high in FODMAPs are gradually reintroduced (one by one) in a controlled manner (to determine exactly which FODMAPs are causing symptoms and to establish tolerance levels).
  1. Personalisation phase. A personalised eating plan is developed based on the results of the inclusion phase. This plan includes only FODMAPs that are well tolerated by the body, thus allowing a diverse diet while controlling the symptoms of IBS or SIBO.

High and low FODMAP foods


High FODMAP foods

Low FODMAP alternatives


Artichokes, asparagus, cabbage, cauliflower, Brussels sprouts, butternut squash, broccoli, green peas, sugar snap peas, mushrooms, garlic, onions, leeks, karela, fennel, okra.

Aubergines, green beans, bok choy, green peppers, carrots, cucumbers, lettuce, potatoes, courgettes, courgettes, alfalfa, celery, chives, cucumbers, olives, parsnips, radishes, spinach, pumpkins, sweet potatoes, tomatoes, turnips, water chestnuts, yams.


Apples, apple juice, cherries, blackberries, blueberries, figs, grapes, dried fruit, mangoes, nectarines, peaches, pears, plums, and watermelons.

Cantaloupe, kiwi (green), mandarins, oranges, pineapple, unripe bananas, grapefruit, lemons, limes, melons, passion fruit, and strawberries.

Dairy products and alternatives

Cow’s milk, cream, custard, condensed milk, ice cream, soya milk (from whole soya beans), yoghurt, soft and fresh cheeses (cottage cheese, ricotta, etc.), whey protein.

Almond milk, hard and aged soft cheeses (such as Brie and Camembert), lactose-free milk, and soya milk (from soya protein).

Protein sources

Most legumes, marinated or seasoned meats and seafood (containing garlic, onions or spice mixtures, etc.) and industrially produced meat products.

Eggs, firm tofu, cooked or steamed meat and seafood, tempeh.

Breads and cereals

Wheat/rye/barley bread, amaranth, breakfast cereals, pancakes, pasta, tortillas, waffles, biscuits and ready-made snacks.     

Cornflakes, oat flakes, quinoa flakes, quinoa/rice/corn pasta, rice bread, spelt sourdough bread, bread without wheat/rice/barley flour, sorghum, tapioca.

Sugar, sweeteners and confectionery

Anything containing high fructose corn syrup, agave nectar, honey, isomalt, malt extract, maltitol, mannitol, molasses, sorbitol, xylitol and xylitol.

Dark chocolate, maple syrup, rice malt syrup, table sugar, stevia.

Nuts and seeds

Cashews and pistachios.

Macadamia nuts, peanuts, walnuts, cedar seeds, pumpkin seeds and sesame seeds.


Coconut water, fortified wines, rum, fruit juices, kombucha, oat milk, soft drinks with corn syrup, soya milk, and tea (chai, chamomile, fennel).

Water, coffee and green, black or white tea.


This list is not complete.


Each person reacts differently to these products – some products high in FODMAPs may not cause any symptoms while others, even in small doses, may make you very uncomfortable.


Key takeaways

FODMAPs are fermentable carbohydrates that are not digested.

Many foods containing FODMAPs are very healthy and some FODMAPs act as prebiotics that promote the activity of friendly gut bacteria.

Therefore, those who do not have digestive problems with these types of carbohydrates should not avoid them.


However, for people intolerant to FODMAPs, products high in these carbohydrates may cause unpleasant digestive upset.

To find out exactly which FODMAPs cause this disorder – all products high in FODMAPs should be excluded from the diet or limited for about 4 weeks.

Then, by eating them again one by one, you can identify which products are causing you indigestion and exclude them from your diet or reduce their consumption in the future.

In other words, if you experience frequent indigestion that reduces your quality of life, FODMAPs could be on the suspect list.


Although a low-FODMAP diet is unlikely to fix all your digestive problems, there is a good chance that identifying the ‘main culprits’ will make a big difference.


As the FODMAP diet can be difficult in the first, elimination phase, it is essential to work with a dietitian or nutritionist to ensure proper adherence to the diet.


Eat tasty, eat balanced and – be healthy!

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