Foods high in fructans and mannitol most commonly trigger IBS symptoms in patients, according to a blinded reintroduction phase trial for the low FODMAP diet.

The Belgium-led study, which included an Australian researcher, also confirmed that symptoms significantly improved by following a low FODMAP diet.

Researchers recruited 117 patients (mean age 36, 84% female) with an IBS diagnosis who followed a six-week strict low-FODMAP diet before responders entered a nine-week blinded randomised reintroduction phase.

The reintroduction phase involved six FODMAP powders (fructans, fructose, galacto-oligosaccharides, lactose, mannitol, sorbitol) or glucose as a control.

Powders were administered in daily amounts in a cross-over order with a two-day wash-out period between each powder at the end of day seven.

Patients completed daily symptom diaries and questionnaires for quality of life and psychosocial co-morbidities. A FODMAP-trigger was defined as a rise of ≥50 points on the IBS Severity Scoring System (IBS-SSS).

Findings published in Gastroenterology [link here] revealed that IBS-SSS improved significantly after the elimination period compared to baseline (150 [mild IBS severity] versus 301 [severe IBS severity], 80% responders).

Symptom recurrence was triggered in 85% of patients who entered the reintroduction phase by an average of 2.5 different FODMAPs per patient.

The most prevalent triggers were fructans (56%) and mannitol (54%), followed by galacto-oligosaccharides (35%), lactose (28%), fructose (27%), sorbitol (23%), and glucose (26%).

There was a significant increase in abdominal pain at day 1 for sorbitol and mannitol, day 2 for fructans and galacto-oligosaccharides, and day 3 for lactose. However, no significant increase was observed for fructose.

Bowel movement frequency significantly increased at day 1 for mannitol, day 2 for galacto-oligosaccharides and fructans, and day 3 for lactose.

Further, scores for abdominal pain duration and severity and bloating were statistically significantly lower during the washout periods compared to the reintroduction for all FODMAPs, but not for glucose, the researchers noted.

“Mannitol and fructans were identified as the most prevalent triggering FODMAPs in this IBS cohort. However, the very heterogeneous and individualised pattern of symptom recurrence patterns precludes the concept of focusing only on these two categories when embarking on a low FODMAP diet,” the authors wrote.

“Selectively eliminating only these FODMAPs would lead to missing out identifying additional FODMAP triggers in patients.”

They concluded: “Our study confirmed the significant improvement of IBS symptoms, somatisation, depression, anxiety and quality of life after following a FODMAP elimination period. While FODMAP reintroduction is often time consuming and highly subjective, we demonstrated that the use of a blinded FODMAP powder reintroduction is an effective approach.

“Using this method, FODMAP triggers can be easily detected in a short and objective manner.”