Are you frequently experiencing abdominal pain, bloating, diarrhoea, and/or constipation, and you are unsure of the exact cause? So you went to the doctors, undertook all the appropriate tests and was told that you have Irritable Bowel Syndrome (IBS). This new diagnosis made you feel overwhelmed, so you started researching what you could do to improve these symptoms but still felt baffled.
To provide you with some reassurance and guidance, this blog includes clear evidence-based information to help you better understand the current best treatment for IBS and how you may benefit from a low FODMAP diet.
What are FODMAPs?
Before we explore the characteristics of a low FODMAP diet, we first need to know what FODMAPs are. FODMAPs are a group of short-chain carbohydrates (sugars- oligos-, disa-, mono-saccharides, and polyols) that are found naturally in many foods and food additives 1,2. Some individuals tend to absorb them in the small intestine poorly, and subsequently, they ferment in the large intestines1.
Approximately one in five Australians are diagnosed with this chronic gastrointestinal condition3. Although IBS is more common in females than males, the exact cause of IBS is still unknown 1,3. Despite the uncertainty, studies have highlighted potential contributors to causing IBS symptoms such as gut motility, gut sensitivity, the balance of 'good' and 'bad' bacteria (dysbiosis), leaky gut and gut infections (gastroenteritis)1,4.
FODMAPs are abbreviations for
A process where the bacteria in the large intestines break down the undigested carbohydrates and produce gas as a by-product.
Fructans and GOS- found in foods such as wheat, rye, onions, garlic and legumes/pulses.
Lactose- found in dairy products such as milk, soft cheeses and yoghurt.
Fructose- found in honey, apples, high fructose corn syrups, etc.
Sorbitol and Mannitol- found in some fruit and vegetables and used as artificial sweeteners.
Here are examples of High and Low FODMAP foods
High FODMAP Foods
Low FODMAP Foods
Artichoke, asparagus, cauliflower, garlic, green peas, mushrooms, onion, sugar snap peas
Aubergine/eggplant, beans (green), bok choy, capsicum (bell pepper), carrot, cucumber, lettuce, potato, tomato, zucchini
Apples, apple juice, cherries, dried fruit, mango, nectarines, peaches, pears, plums, watermelon
Cantaloupe, grapes, kiwi fruit (green), mandarin, orange, pineapple, strawberries
Dairy and alternatives
Cow's milk, custard, evaporated milk, ice cream, soy milk (made from whole soybeans), sweetened condensed milk, yoghurt
Almond milk, brie/camembert cheese, feta cheese, hard cheeses, lactose-free milk, soy milk (made from soy protein)
Most legumes/pulses, some marinated meats/poultry/seafood, some processed meats
Eggs, firm tofu, plain cooked meats/poultry/eafood, tempeh
Breads and cereals
Wheat/rye/barley-based breads, breakfast cereals, biscuits and snack products
Oats, quinoa/rice/corn pasta, rice cakes (plain), sourdough spelt bread, wheat/rye/barley free breads
Sugar, sweeteners and confectionary
High fructose corn syrup, honey, sugar-free confectionary
Dark chocolate, maple syrup, rice malt syrup, table sugar
Nuts and seeds
Macadamias, peanuts, pumpkin seeds/pepitas, walnuts
**Contact us or your dietitian for more information on modifying your current diet to a low FODMAP diet.
What happens in the bodies of people with IBS?
When we eat foods containing FODMAPs, the short-chain carbohydrates cannot be broken down and absorbed in your small intestines. Instead, they move slowly through the small intestine, attracting water as they move through to the large intestines. In the large intestine, bacteria use the FODMAPs as an energy source to survive, and they rapidly ferment the FODMAPs, producing gas as a result. The excess water and gas produced in the intestines can cause the intestinal wall to stretch and expand. When the intestinal wall stretches, the highly connected nerves around the intestine detect this stretching and send signals to your brain. These sequential events occur in both people with or without IBS, but the difference is that people with IBS have problems with gut motility and gut sensitivity, exaggerating their responses to FODMAP rich foods. Therefore, since people with IBS have a sensitive intestine, these signals become amplified and contribute to the pain, bloating, distension, wind, constipation, and diarrhoea they experience when consuming high FODMAP foods.
IBS Treatment: Low FODMAP diet
A diverse range of IBS treatments mainly focuses on alleviating the symptoms so IBS sufferers can comfortably live with the condition1,2. It does not, however, cure the condition 2. Among the numerous treatments, the best and most effective treatment is the low FODMAP diet researched by Monash University 5. Many studies have shown consistent findings that a low FODMAP diet can improve gastrointestinal symptoms in up to 3 out of 4 IBS sufferers 4. For instance, one study found that the low FODMAP diet provided symptomatic relief in IBS patients than general dietary strategies involving healthy eating principles, incorporating insoluble and soluble fibres, and limiting sugar-free foods and foods containing sorbitol (86% and 49%, respectively) 6.
The low FODMAP diet involves swapping the high FODMAP foods to low FODMAP alternatives for 2-6 weeks 5. This diet should not be used more than the set period as it is quite restrictive and unsustainable. Once your symptoms have improved, the next step is to reintroduce FODMAP rich foods back into your usual diet one by one to identify which FODMAP types trigger your IBS symptoms and which do not 5. It is highly recommended to use a diary or an app to track which foods you have tested caused you to develop any IBS symptoms for 8-12 weeks 5. After identifying your high FODMAP trigger foods, the well-tolerated foods should be incorporated into a diet that works best for you 5. Ultimately, it's all about finding a good balance between tolerated FODMAP foods and the avoidance of other types in the long-term 5. Nonetheless, in most cases, people find themselves reintroducing high FODMAP foods back into their diet, but they cannot eat them as often or in the same quantity as before 5.
Who should follow the low FODMAP diet?
A low FODMAP diet is a therapeutic diet only intended for people who have been medically diagnosed with IBS 2. It is important that you don't self-diagnose yourself with IBS. Instead, you should visit your doctor, who will assess your symptoms, run tests to exclude any other gut conditions (such as coeliac disease, inflammatory bowel disease, endometriosis and bowel cancer) and give you a clear diagnosis of IBS before you start the diet 2.
To undertake a low FODMAP diet properly, make sure you consult a dietitian for a tailored FODMAP elimination and reintroduction plan since it can be complex and challenging to adjust the new changes to your usual diet 4.
1. Nanayakkara WS, Skidmore PM, O'Brien L, Wilkinson TJ, Gearry RB. Efficacy of the low FODMAP diet for treating irritable bowel syndrome: the evidence to date. Clinical and experimental gastroenterology. 2016;9:131–142.
2. Monash University. FOMAPs and Irritable Bowel Syndrome. [Internet]. Available from: https://www.monashfodmap.com/about-fodmap-and-ibs/
3. Better Health Channel. Irritable bowel syndrome (IBS). [Internet] Reviewed 2021 Dec 20; Available from: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/irritable-bowel-syndrome-ibs
4. Monash University. IBS. [Internet]. Available from: https://www.monashfodmap.com/ibs-central/what-is-ibs/
5. Monash University. IBS Diet. [Internet]/ Available from: https://www.monashfodmap.com/ibs-central/diets/
6. Staudacher HM, Whelan K, Irving PM, Lomer MC. Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet. 2011;24(5):487-95.