The low-FODMAP diet – what is it? What should you eat, and what should you avoid?

The low-FODMAP diet was developed on the basis of research carried out by Australian scientists, and the term ‘FODMAP’ itself first appeared in a publication in 2005. The acronym stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols – a group of short-chain carbohydrates which, in some people, are poorly absorbed in the small intestine. They can then increase the amount of water in the gut and ferment rapidly, which contributes to bloating, flatulence, abdominal pain and changes in bowel habits.

1. Diet and gastrointestinal problems
2. Interpreting symptoms and risky decisions
3. Recommended low-FODMAP foods
4. Products not recommended on a low-FODMAP diet
5. FAQ – frequently asked questions

Diet and gastrointestinal problems

Not all chronic gastrointestinal conditions show abnormal results in routine blood tests, abdominal ultrasound scans or gastroscopies. A good example of this is irritable bowel syndrome, in which, despite normal test results, the patient experiences abdominal pain, bloating, diarrhoea, constipation or a feeling of fullness. Depending on the clinical picture, the doctor may then consider, amongst other things, coeliac disease, inflammatory bowel disease, lactose intolerance or infections.

Interpreting symptoms and risky decisions

The difficulty also lies in the fact that symptoms can vary from day to day and depend on the size of the meal, stress, sleep, physical activity and certain foods eaten together. The mere fact that discomfort occurs after eating a particular food does not necessarily indicate an allergy or a permanent intolerance to that food. For this reason, some people start to eliminate milk, bread, fruit, pulses or other entire food groups from their diet on their own. The more such eliminations there are, the more difficult it becomes later on to identify the actual trigger of the symptoms, and the diet may become rather monotonous, increasing the risk of an insufficient intake of certain nutrients. One structured approach to temporarily limiting foods that may exacerbate symptoms is the low-FODMAP diet.

Recommended low-FODMAP foods

The low-FODMAP diet can include, amongst other things, rice, potatoes, oat flakes, quinoa, buckwheat and carefully selected gluten-free or spelt sourdough bread. Vegetables that are low in FODMAPs, when eaten in appropriate portions, include carrots, cucumber, aubergine, lettuce, spinach, potatoes, courgettes and green peppers. Fruits you can choose from include kiwis, oranges, mandarins, pineapple, strawberries and less ripe bananas. For many foods, the classification depends on portion size; therefore, lists of low-FODMAP foods should not be treated as an absolute distinction between permitted and prohibited foods.

Meat, fish, eggs and natural oils contain virtually no FODMAPs in themselves. However, ready-made marinades, sauces and spice mixes containing onion, garlic, honey or other FODMAP-rich ingredients can be problematic. When it comes to dairy products, it is more common to choose lactose-free milk and yoghurts, as well as hard and mature cheeses, which naturally contain very little lactose.

Estimated FODMAP content in the main sources

Products not recommended on a low-FODMAP diet

Foods that are usually restricted during the first phase include onions and garlic, larger portions of wheat and rye products, some pulses, ordinary milk and certain fresh dairy products, as well as apples, pears, mangoes, watermelon and dried fruit. Honey, agave syrup, inulin, chicory root fibre and polyols used as sweeteners – such as sorbitol, mannitol, xylitol and maltitol – can also be sources of high levels of FODMAPs. These are often found in chewing gum, sweets, bars and other products labelled ‘sugar-free’.

The low-FODMAP diet is not a gluten-free diet. In the case of wheat, the restriction stems primarily from the presence of fructans, rather than gluten; therefore, a person without coeliac disease or any other medical indication does not automatically need to eliminate gluten. Nor is there a single, fixed list of ‘allowed’ and ‘forbidden’ foods, as portion size, the variety of the product, its degree of ripeness and how it has been processed all play a role.

"The low-FODMAP diet should not be treated as a list of foods that are forbidden for life. Its main aim is to temporarily restrict selected fermentable carbohydrates, and then to assess individual tolerance and diversify the diet as much as possible." Anna Zięba – Dietitian

FAQ – frequently asked questions

Is the low-FODMAP diet mainly intended for people with IBS?

Irritable bowel syndrome (IBS) is one of the best-researched conditions for which the low-FODMAP diet is used. It may help some people to reduce symptoms such as bloating, abdominal pain or irregular bowel movements. However, this does not mean that everyone with gut problems should automatically start following it.

How long can you follow a low-FODMAP diet?

The most restrictive phase is a temporary stage, not a way of eating intended for indefinite use. Afterwards, individual FODMAP groups are gradually reintroduced to test tolerance and create as varied a meal plan as possible, tailored to the individual.

Do you have to give up bread completely on the low-FODMAP diet?

No. What matters is the type of bread, its ingredients and portion size. The restriction on some wheat and rye products is primarily due to their fructan content, rather than the mere presence of gluten.

Is the low-FODMAP diet a gluten-free diet?

No. They are two different dietary approaches. A person without coeliac disease or other medical reasons to exclude gluten does not need to eliminate it simply because they are following a low-FODMAP diet. However, some gluten-free products are a convenient choice as they may also contain small amounts of FODMAPs.

Can you eat fruit on a low-FODMAP diet?

Yes. In appropriate portions, you can choose from kiwis, oranges, mandarins, strawberries, pineapple and less ripe bananas, amongst others. With FODMAP, portion size is very important, which is why the same food may be well tolerated in small quantities but cause symptoms when eaten in larger portions.

Are dairy products off-limits?

No. The main issue is the lactose present in certain dairy products. You can therefore choose lactose-free products, as well as some hard and mature cheeses, which naturally contain very little lactose.

Why can ‘sugar-free’ products cause bloating?

Some contain polyols, such as sorbitol, mannitol, xylitol or maltitol. These are classified as FODMAPs, and in sensitive individuals, larger amounts may increase the amount of water in the gut and contribute to bloating, gas and looser stools.

Can you start a low-FODMAP diet on your own?

For mild symptoms, you can start by keeping track of the foods you eat and your portion sizes, but for chronic or severe symptoms, it is worth identifying the cause first. Long-term self-imposed elimination of many foods may unnecessarily restrict your diet. Medical advice is particularly necessary in cases of weight loss, blood in the stools, anaemia, fever or other worrying symptoms.

Source:

• Muir, J. G., Rose, R., Rosella, O., Liels, K., Barrett, J. S., Shepherd, S. J., & Gibson, P. R. (2009). Measurement of short-chain carbohydrates in common Australian vegetables and fruits by high-performance liquid chromatography (HPLC). Journal of agricultural and food chemistry, 57(2), 554–565. https://doi.org/10.1021/jf802700e
• Whelan, K., Martin, L. D., Staudacher, H. M., & Lomer, M. C. E. (2018). The low FODMAP diet in the management of irritable bowel syndrome: an evidence-based review of FODMAP restriction, reintroduction and personalisation in clinical practice. Journal of human nutrition and dietetics : the official journal of the British Dietetic Association, 31(2), 239–255. https://doi.org/10.1111/jhn.12530
• Sultan, N., Varney, J. E., Halmos, E. P., Biesiekierski, J. R., Yao, C. K., Muir, J. G., Gibson, P. R., & Tuck, C. J. (2022). How to Implement the 3-Phase FODMAP Diet Into Gastroenterological Practice. Journal of neurogastroenterology and motility, 28(3), 343–356. https://doi.org/10.5056/jnm22035