Understanding IBS: Foundations, FODMAPs and other approaches
Bloating, tummy pain and unpredictable bowel habits can make everyday life hard. If you have been told you have IBS, or think you might, you have probably heard of the low FODMAP diet. Here is a simple guide to what IBS is, what FODMAPs are, and where the low FODMAP diet fits in.
There is no one size fits all approach to IBS. Many people find relief with simple foundations and an approach tailored to their symptoms, without needing a strict diet.
Irritable bowel syndrome (IBS) is a common gut condition. Depending on how it is defined, it affects around 4 to 9% of people worldwide, and it is more common in women.1 Symptoms can include abdominal pain, bloating, wind, diarrhoea, constipation, or a mix of both.
IBS is now described as a "disorder of gut brain interaction".2 This means the gut and brain communicate differently, and the gut can become more sensitive. Normal sensations, such as gas or stretching after a meal, may be felt more strongly. It also explains why stress so often makes symptoms worse.
Many women also notice their IBS symptoms change across their menstrual cycle, and are often worse around their period. This is thought to be linked to changing hormone levels, which can make the gut more sensitive.3
IBS should always be diagnosed by a doctor
Many other conditions can cause similar symptoms, such as coeliac disease or inflammatory bowel disease. A doctor will look at your symptoms and history and may do some tests to rule these out.4 It is important not to self diagnose, and to see your GP if you notice new or changing symptoms.
IBS guidelines recommend starting with simple diet and lifestyle changes before trying the low FODMAP diet.5 For many people, these alone make a real difference:
- Eat regularly, without skipping meals, and eat slowly in a relaxed setting
- Drink enough fluid, around 8 cups a day
- Adjust your fibre, as soluble fibre (such as oats, chia, linseed and psyllium) is often better tolerated than insoluble fibre (such as wheat bran)4
- Keep caffeine and alcohol moderate
- Move regularly, as increasing physical activity has been shown to improve IBS symptoms6
- Manage stress and support sleep, given the strong gut brain connection
FODMAPs are a group of carbohydrates found in many everyday foods. The name stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols. They are not absorbed well in the small intestine, so they move into the large intestine, where gut bacteria ferment them and produce gas.7
Common sources include onion, garlic, wheat, legumes, milk, apples, pears, honey and some sugar free products.7 FODMAPs are not bad for you. In fact, many are great for gut health. In a sensitive gut, though, the gas and water they create can trigger symptoms.
The low FODMAP diet has three steps:7
- Reduce: FODMAPs are limited for a short period, usually 2 to 6 weeks
- Reintroduce: FODMAP groups are tested one at a time to find your personal triggers
- Personalise: tolerated foods are added back, and only the true triggers are limited
No food groups are cut out
It is important to note that the low FODMAP diet is not about cutting out whole food groups. All food groups stay in, and lower FODMAP options are simply chosen within each one. For example, lactose free milk instead of regular milk, or oats and rice instead of wheat based foods. Without careful planning, it is easy to miss out on nutrients such as calcium, iron and fibre.7 This is one of the main reasons it is so important to work with a dietitian.
How well does it work?
Around 3 in 4 people with IBS find the low FODMAP diet improves their symptoms.7 That also means around 1 in 4 people do not notice much benefit, which is why it is not the answer for everyone.
Why is it only short term?
Many FODMAPs feed the beneficial bacteria in your gut. Following the reduce phase for too long can lower levels of helpful bacteria, such as bifidobacteria, reduce diet quality and make it harder to meet your nutrient needs.8 The reintroduce and personalise steps are what restore variety, and most people can eat many FODMAP foods again.8
Who is it not suitable for?
The low FODMAP diet is not recommended for everyone. It may not be suitable if you:8
- Have a current or past eating disorder
- Already follow a very restricted diet
- Have unexplained weight loss or are underweight
- Mainly experience constipation
A gentler option
A full low FODMAP diet is not always needed. Often, a modified or "gentle" low FODMAP approach can be trialled instead, where only a few of the most likely trigger foods are reduced rather than all FODMAPs at once.8 Working with a dietitian can help you decide which approach, if any, is the best fit for you.
Gut directed hypnotherapy is an alternative, evidence based approach for IBS that works by calming the gut brain connection. In a Monash University trial, it improved IBS symptoms as much as the low FODMAP diet.9
Nerva is an app that uses this approach at home over six weeks. It was developed from Monash University research, and clinical studies have shown it can meaningfully improve IBS symptoms.10 It can be a helpful alternative to the low FODMAP diet.
Nula Nutrition is trained in using Nerva with clients and can provide a referral for 25% off the program. Nula Nutrition receives no financial benefit from this referral.
Want support with IBS?
Nula Nutrition can help you work through the foundations, decide whether the low FODMAP diet is right for you, and guide you through each step. The approach is always evidence based and tailored to you. Registered dietitian consultations are available for women's health in Calgary and online across Alberta, including Canmore, Banff, Edmonton, and Cochrane.
Ready to get personalised nutrition support?
Book a Free Discovery CallWritten by Madison Hows RD APD
References
1. Oka P, Parr H, Barberio B, Black CJ, Savarino EV, Ford AC. Global prevalence of irritable bowel syndrome according to Rome III or IV criteria: a systematic review and meta-analysis. Lancet Gastroenterol Hepatol. 2020;5(10):908-917.
2. Drossman DA, Hasler WL. Rome IV: functional GI disorders: disorders of gut-brain interaction. Gastroenterology. 2016;150(6):1257-1261.
3. Heitkemper MM, Chang L. Do fluctuations in ovarian hormones affect gastrointestinal symptoms in women with irritable bowel syndrome? Gend Med. 2009;6(Suppl 2):152-167. PMID: 19406367
4. Lacy BE, Pimentel M, Brenner DM, et al. ACG clinical guideline: management of irritable bowel syndrome. Am J Gastroenterol. 2021;116(1):17-44.
5. McKenzie YA, et al. British Dietetic Association systematic review and evidence-based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update). J Hum Nutr Diet. 2016;29(5):549-575. PMID: 27272325
6. Johannesson E, Simrén M, Strid H, Bajor A, Sadik R. Physical activity improves symptoms in irritable bowel syndrome: a randomized controlled trial. Am J Gastroenterol. 2011;106(5):915-922.
7. Canadian Digestive Health Foundation. Understanding the low FODMAP diet: foods, phases and tips for managing IBS.
8. Lomer MCE. The low FODMAP diet in clinical practice: where are we and what are the long-term considerations? Proc Nutr Soc. 2024;83(1):17-27.
9. Peters SL, Yao CK, Philpott H, Yelland GW, Muir JG, Gibson PR. Randomised clinical trial: the efficacy of gut-directed hypnotherapy is similar to that of the low FODMAP diet for the treatment of irritable bowel syndrome. Aliment Pharmacol Ther. 2016;44(5):447-459. PMID: 27397586
10. Anderson EJ, Peters SL, Gibson PR, Halmos EP. Comparison of digitally delivered gut-directed hypnotherapy program with an active control for irritable bowel syndrome. Am J Gastroenterol. 2025;120(2):440-448. PMID: 38940439
