The re-challenge phase of a low FODMAP diet is crucial to establishing a nutritionally adequate diet in patients with IBS as well as providing some certainty regarding the food triggers responsible for their symptoms.

According to an article in the Journal of Gastroenterology and Hepatology, the goal is to find a balance between IBS symptom control and optimal expansion of the diet.

Coauthor Ms Caroline Tuck, an accredited practising dietitian and PhD candidate at Monash University, said having more food choices could also relieve anxiety and help patients enjoy occasions such as eating out.

“Despite the fact patients might be feeling great if they have responded to the strict low FODMAP diet, we don’t want people to stay on it long term, ” she said.

“Re-challenging helps identify the specific food triggers for patients and deliver them an individualised, modified version of the low FODMAP diet. “

Ms Tuck said an initial re-challenge program – one food group at a time, with 2-3 day wash-out periods, and gradual increases in quantity or frequency of foods – can take 6 to 8 weeks.

She told the limbic patients’ food preferences and suspicions about their triggers often guided which foods to introduce first.

“The evidence is limited on how to reintroduce food and which are more or less likely to cause symptoms. Foods with higher FODMAP content such as onion and garlic may be more likely to cause symptoms but we need more long-term studies, ” she said.

However dieticians can help reassure and encourage patients by explaining they were now better equipped to cope with food challenges because their symptoms had been brought under control by the restriction diet.

She said dietitians could also manipulate the re-challenges to be less anxiety provoking by providing practical tips.

“It is a bit of a trial and error approach but patients are usually understanding. For example, in patients who are particularly anxious, we might start them with really small amounts of food such as a splash of milk in their cup of tea.”

 She said leveraging the community interest in the microbiome and prebiotic foods was another way to explain to patients the importance of re-challenges and expanding their diet.

Patients with additional dietary requirements such as vegetarians or people living with diabetes may need to preferentially introduce foods of the highest nutritional concern.