Before research on the low FODMAP diet began at Monash University close to 14 years ago, there were inconclusive findings on which food components impacted irritable bowel syndrome.
With consistent findings that “70 to 80 per cent of individuals with IBS will respond positively to a low FODMAP diet,” it has become “first-line therapy for IBS,” in Australia, according to Sydney-based gastroenterologist Dr Adrian Sartoretto.
“Led by Professor Peter Gibson, Monash has done [important work] in figuring out what people are responding to in their diets,” with the low FODMAP diet gaining international recognition.
What are FODMAPs?
“FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are groups of diverse carbohydrates naturally occurring in all sorts of foods, often healthy foods,” Dr Sartoretto said.
Fructose is one type of FODMAP, found in foods including apples, dried fruit and honey.
“Humans don't absorb fructose particularly well, so [foods naturally] rich in this sugar tend to be incompletely digested. This leads to fermentation of the sugar by gut bacteria, producing gas and leading to fluids shifts within the intestine. In sensitive people, this manifests as bloating, excess gas, abdominal pain and either diarrhoea or constipation, depending on their bowel's reaction to the stimulus.”
Other FODMAPs, such as lactose in milk, and polyols in stone fruit can have a similar effect.
“Monash has also found that it’s often not gluten, but a common FODMAP group called fructans - found in wheat, onions and garlic - that tend to drive symptoms in what was previously referred to as non-coeliac gluten sensitivity.”
What does the diet involve?
“The first stage…is quite strict, [excluding] all FODMAP sources; an important phase because it tells if you will respond to the diet,” Dr Sartoretto said.
“The first phase isn’t balanced or nutritionally adequate (high FODMAP foods are often high in fibre and prebiotics, which encourage good gut bacteria), and it’s hard to have a meal out with friends.”
In the second stage, “foods are reintroduced one by one to figure out which foods are causing problems, and in what quantity. Excluding FODMAPs completely is not the aim of this dietary approach.”
The role FODMAPs play in IBS differ to a food allergy, where a small amount of an allergen can cause an allergic reaction, Dr Sartoretto said.
“FODMAPs have a threshold effect. Keep the FODMAPs you’re sensitive to below your [personal] threshold and you won’t have symptoms.”
The input of an accredited practising dietitian is important because it is a “very complex diet,” Dr Sartoretto said.
Monash’s Low FODMAP Diet App can assist in identifying the FODMAP content of numerous foods, and help to identify thresholds.
What if the low FODMAP diet doesn’t work?
“There are a number of supplements [with] proven benefit in IBS…peppermint oil and Iberogast®, both available over-the-counter, can help with [stomach] pain and bloating,” Dr Sartoretto said.
“Probiotics may help in some cases, but they should only be used for a month or so as use beyond this period does not confer additional benefit.
“Cognitive Behaviour Therapy and low dose anti-depressants can reduce symptoms due to the link between anxiety and IBS.
“Antibiotics are a lot further down the list of treatment options due to side effects and antibiotic-resistance.”
Energast®, a new over-the-counter supplement contains butyrate, “a fermented product [important for nourishing the bowel lining and reducing] bowel inflammation. This may have a role in improving symptoms of IBS in some,” especially for diarrhoea that isn’t alleviated with a low FODMAP diet, Dr Sartoretto said.
“If symptoms are not adequately controlled with these measures, a gastroenterologist should be consulted to exclude other pathology (causes), if not already done.”
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