IBS & The Low FODMAP Diet

Published on 2nd October 2020

This article was first published in October 2019 Thriva Newspaper.

Irritable bowel syndrome (IBS) is a disorder which occurs when a person has specific ongoing gut issues despite ruling out other medical conditions, like coeliac disease or inflammatory bowel disease.

Up to 20% of people are thought to suffer with IBS, and this seems to occur more often in women than men (1-2).

Common symptoms of IBS include:

Diarrhoea
Constipation
Bloating
Wind
Stomach pain
Cramps

If you suspect that you might have IBS, it is important to see your doctor to get an official diagnosis, as well as ruling out other medical conditions.

Stress management, relaxation, regular exercise and dietary changes can play a big role in the overall management of IBS.

First-line Diet Advice for IBS

Before embarking on a more specific diet, there are some key diet principles to follow.

One of the most important things to do is eating regular meals, avoiding long gaps between meals, avoid rushing meals and chewing each mouthful well before swallowing (roughly 20 chews per mouthful).

For those who suffer with constipation it can be helpful to gradually increase fibre intake, while also drinking plenty of fluid. Consuming golden linseeds can also be helpful for those with constipation and bloating.

Whereas some people with IBS who mainly experience diarrhoea may benefit from reducing their intake of wholegrain cereals and bran.

However, diet triggers for IBS can vary a lot, so it can be useful to keep a food and symptom diary to try to identify your triggers. A Registered Dietitian can support you with this process.

Probiotics can sometimes be helpful, but this is very individual so it is best to try one type of probiotic at a time and to consume this every day for at least four weeks.

For more information on the first diet steps to take with IBS the British Dietetic Association (BDA) has a food fact sheet called ‘Irritable Bowel Syndrome and Diet’.

The Low FODMAP Diet

If first-line changes don’t lead to much of an improvement in IBS symptoms, the next option is to try a low FODMAP diet with support from a Dietitian – this should not be attempted alone as it is a specific and restrictive diet.

FODMAPs are a group of poorly-digested carbohydrates which are associated with worsening IBS symptoms by drawing water into the small intestine and producing gas in the large intestine (3).

FODMAP stands for:

Fermentable (i.e. able to be fermented and used as food for gut bacteria)
Oligosaccharides (i.e. a type of carbohydrate which usually contains 3-10 simple sugar molecules, this refers to fructans which are found in onions, garlic, wheat, rye and barley; and GOS which is found in beans and lentils)
Disaccharides (i.e. a type of carbohydrate which contains 2 simple sugar molecules, this refers to lactose which is found in milk and yoghurt)
Monosaccharides (i.e. a type of carbohydrate which contains 1 sugar molecule, this refers to fructose which is found in honey, apples and pears)
And
Polyols (also known as ‘sugar alcohols’, this refers to sorbitol and mannitol which are mainly found in sugar-free sweets, mints and chewing gum, as well as certain fruit and vegetables)

There are 3 stages to the low FODMAP diet:

Elimination phase: FODMAPs are excluded for 4-6 weeks.
Reintroduction phase: High FODMAP foods are introduced one at a time to find out which FODMAPs, and which amount of these, trigger IBS symptoms.
Personalisation phase: The diet is personalised to avoid the main IBS triggers, in the least restrictive way possible.

This diet has been found to improve gut symptoms in those with IBS 70-80% of the time, and seems to be most effective for those with diarrhoea, pain and bloating (3).

However, it isn’t clear whether this improvement continues after 18 months, this diet isn’t suitable for everybody and the restrictive phase of the diet shouldn’t be followed for more than 6 weeks (3).

It is also important to re-test FODMAP triggers every few months as tolerance can change over time.

If you are interested in trying the low FODMAP diet it is really important to seek support from a Registered Dietitian who has training and experience in this area.

References

Khanbhai & Singh Sura (2013) “Irritable Bowel Syndrome for Primary Care Physicians”. BJMP 2013;6(1):a608.
Saha (2014) “Irritable bowel syndrome: Pathogenesis, diagnosis, treatment, and evidence-based medicine” World J Gastroenterol. 20(22): 6759–6773.
Altobelli et al. (2017) “Low-FODMAP Diet Improves Irritable Bowel Syndrome Symptoms: A Meta-Analysis” Nutrients. 9(9): 940.

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