What is a low-FODMAP diet?
FODMAP is an acronym for a certain class of carbohydrates, called fermentable short-chain carbohydrates. The low FODMAP diet has been shown to reduce symptoms in around 70% of those with irritable bowel syndrome (IBS)1
It stands for:
Oligosaccharides (e.g. wheat, onion, garlic, pulses)
Disaccharides (e.g. milk, yohgurt)
Monosaccharides and (e.g. honey, mango)
Polyols (e.g. cauliflower, celery, avocado, sweetcorn)
FODMAPs are not easily digested in the gut and thus entice water into the small intestine, and when they move down into the large intestine they are fermented by gut microbes, which can increase gas production. For some people with IBS, they appear to be extra sensitive to these effects. This is most likely due to what is called visceral hypersensitivity.
Visceral hypersensitivity is an increase in pain sensation experienced in internal organ such as the bowel. Essentially an internal stimulus (e.g. FODMAP, but also common triggers such as coffee, alcohol, high fat foods, stress, anxiety) can register to you as severe pain, bloating, flatulence, change in bowel habit, which is non-IBS sufferers would maybe only be mild discomfort.
Are FODMAPs bad for everyone?
This is 100% false! These foods are in fact some of your gut microbes favourite foods or mostly prebiotics. If you can include them in your diet it appears very important for long term gut health to do so.
What does a low-FODMAP diet consist of?
The diet has three phases:
The elimination phase: restrict high FODMAP foods for 2-6 weeks (average 4 weeks). If you look at the list of foods to avoids you may feel initially overwhelmed, but there are still lots of foods you can still eat. Your dietitian is also able to tailor the plan to your individual needs.
The reintroduction phase: If you respond to the elimination phase, you’ll then begin the reintroduction phase, in which you systematically add foods back in to understand your personal tolerance to each high FODAMP group (it’s mostly some rather than all FODMAPs that you need to avoid long term and there is a great deal of difference in individual tolerance levels). This can take anywhere from 4-10 weeks to complete.
The maintenance phase: This will be the threshold of total FODMAPs you can consume whilst keeping your symptoms at bay.
What should I do before starting the low-FODMAP diet?
Consult a reliable healthcare provider! Whether you’ve already been diagnosed with a gastrointestinal (GI) disease or you are just beginning to explore possible causes and cures for your symptoms, your doctor and a registered dietitian can help set you in the right direction. They may have alternative ideas to test before you try the diet. They can also help guide you through the nuances of the diet, provide shopping and menu guides and troubleshoot when questions or problems arise. There’s a lot to keep track of with this diet, including different quantities and portion sizes for different foods. It’s easier to follow successfully if you have a guide who knows the way around. And nearly all published studies have shown the benefits of the low FODAMP diet when the diet was followed with guidance form a dietitian.
Is the low FODMAP diet the best choice for you?
The truth is that the low FODMAP diet is quite a complex diet can be difficult to follow solo. It may also not be for everyone. In fact, you should only try and low FODMAP diet when you have found the following first line interventions to not give you satisfactory relief: 2
A recent study found that first line interventions are just as effective as the Low FODMAP (and gluten free!) diet and people found it cheaper, easier to follow and more socially acceptable, as show here:
|Source: Rej et al, 2022|
What are the unforeseen consequences and risks of following a low FODMAP diet?
These are generally unseen when you first hear of the low FODMAP diet but are manifold and include:
1.some psychosocial implications including social isolation, perceived difficulties with travel and eating out.
2.the additional cost of specialty food items with some estimates of foods being 20% more expensive and so your budget may not allow for it.
3.the risk of increasing food fear or disordered eating behaviours, particularly if these are an ongoing issue or there is a history of issues in the past.
4.putting all your eggs in the ‘diet basket’ – thinking that your IBS symptoms are all related to food, when we know that this is usually not the case (stress, anxiety, hydration, alcohol, physical activity, sleep hygiene, meal pattern and how you eat can all play active roles in triggering symptoms)
5.increased risk of nutrition deficiencies. In my Gut Health Clinic, I frequently observe lower than recommended intakes of a range of nutrients and in particular fibre and calcium!
6.Likely negative effects on your microbiota should you stay on the restrictive phase too long
Following the low FODMAP diet with support from a dietitian can make it much easier to follow the diet and overcome most of the risks and challenges and help you interpret the results. This infographic clearly defines the role of your dietitian – and I hope you’ll agree that it’s more than giving out a list of yes and no foods!
Source: Gibson, et al. 2022
Unfortuantely, I have witnessed so many people who have ventured into the low FODMAP territory alone and have not been able to reintroduce high FODMAP foods back into their diet, have become more malnourished and lack enjoyment and pleasure from eating. And to top it off, still suffer with a whole raft of gut symptoms and the bowel is still erratic. In fact, in a study with people who followed the diet without a dietitian highlighted ‘low compliance to the diet and a wish for dietician support’ 5
An individual assessment will helps decide the best intervention for you and support you along each step. If it’s not the low FODMAP diet, remember that there are many other avenues to take!
1.Halmos et al. Gastroenterology 2014; 146: 67–75.e5.
2.National Institute for Health and Care Excellence (NICE). Irritable bowel syndrome in adults. 3rd ed. London: National Institute for Health and Care Excellence (NICE); 2017.
3.Rej et al, Clinic Gastro & Hep, 2022, 20 (12), p2876
4.Gibson, et al. Journal of Gastroenterology and Hepatology, 2022; 37: 644– 652.
5.Hill et al. Gastroenterol Hepatol (N Y). 2017;13(1):36–45