Getting the FODMAP diet balance right

Meet the researchers who helped develop the most powerful dietary treatment for IBS yet

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The low FODMAP diet is a useful diagnostic tool, but it’s not a healthy long-term diet, Monash University researchers say.

“It’s not like gluten-free for coeliac disease, where it’s a strict, life-long diet,” Associate Professor Jane Muir, a nutrition scientist and dietitian, said.

“It’s a three-step diet and you are actually only on a low FODMAP intake for two to six weeks and then you start to bring foods back in, identify what are your trigger FODMAPs, and then you personalise the diet, so you end up with a much less restrictive diet.”

Patients should only undertake the low FODMAP diet if they had received a diagnosis of irritable bowel syndrome (IBS) and they were under the supervision of a dietitian, Professor Muir said. “We do not want people going on this diet who do not need to go on this diet,” she said.

Cutting down on FODMAPs can have implications for some important biological functions. Fructans have been shown to promote healthy gut bacteria. A healthy gut microbiome is believed to suppress the growth of potential pathogens in the colon, increase calcium absorption and ease diarrhoea.

“We actually want people to have as many FODMAPs as they can possibly tolerate, but everyone will have their own level of tolerance,” Professor Muir said.

Gluten-free diets have risen in popularity in recent years as a way to self-treat irritable bowel syndrome.

But it’s probably the lesser-known sugars inside wheat products that are causing most gut problems, researchers say. “It is the FODMAP component that is probably triggering symptoms, not the gluten at all,” Professor Muir said.

Professor Muir is part of a team at Monash University that has been studying the effect of FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) on people with IBS for over a decade.

The team has discovered that personalised, low FODMAP diets improve symptoms in a majority of patients with IBS. FODMAPs are poorly absorbed, short-chain carbohydrates that are rapidly fermented by bacteria in the large intestine.

Most people poorly absorb these chemicals, but for a variety of reasons, for people with IBS the fermentation of FODMAPs can lead to gas production, abdominal discomfort, pain, bloating, diarrhoea or constipation.

The FODMAP family includes nine different short-chain carbohydrates, including fructose in excess of glucose, lactose, sorbitol, mannitol, fructans, galacto-oligosaccharides.

People with IBS can be sensitive to one or several of these FODMAPs.

Malabsorption of fructose, lactose and sorbitol can be identified through a breath test, which measures the amount of gas in the breath in people who have consumed a set portion of each sugar.

However, breath testing is an unreliable method to determing FODMAP sensitivities.

“We instead recommend the three phases of the FODMAP diet: 1) low FODMAP diet to induce IBS symptom control, 2) FODMAP reintroduction to identify which FODMAPs trigger symptoms and which do not, 3) FODMAP personalisation,” said Dr Jane Varney (PhD), a research dietitian at Monash University.

“Well-tolerated FODMAPs are brought back into the diet and poorly-tolerated FODMAPs [are] rerestricted but only to a level required to maintain adequate symptom control.”

Around 75% of patients with IBS benefited from a low-fructose diet in an Australian study of 62 people published in 2006. Since then, a number of studies have expanded those findings to other FODMAPs. “The low FODMAP diet has a very strong scientific evidence base,” Professor Muir said.

“It’s becoming more popular as first-line therapy now to treat IBS in many countries. Patients like it because it gives the control back to them.”

Unfortunately, there are no hard and fast rules to help patients sort the high-FODMAP foods from the low-FODMAP foods.

FODMAPs are found in high concentrations in all sorts of products, including garlic, mushroom, onions, wheat products, marinated meats, cow’s milk, yogurt, soy milk, legumes, honey, cashews and pistachios.

Low FODMAP foods includes carrots, cucumbers, lettuce, potatoes, tomatoes, grapes, oranges, strawberries, pineapple, some cheeses, eggs, tofu, oats, dark chocolate, peanuts, walnuts and macadamias. (Plain meat, oils and fats don’t contain FODMAPs.)

Monash University has individually tested the FODMAP content of many staple Australian foods, and conveniently packaged that information into a smartphone app, which also contains over 80 low-FODMAP recipes.

The app costs about $13, and the proceeds go towards further IBS research.