Do different FODMAPs have different effects?

Figs have a very high excess fructose rating
& pomegranates are rated 'red' for fructans

By Caroline Tuck (APD, PhD Candidate, Department of Gastroenterology)

Do different FODMAPs have different effects?

FODMAP is an acronym for a group of carbohydrates that have been shown to cause symptoms in people with irritable bowel syndrome (IBS). The acronym stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols and includes the following carbohydrates:

• fructose
• lactose
• sugar polyols (including sorbitol and mannitol)
• fructans
• galactooligosaccharides

Although these five sugar subgroups have been grouped together, they appear to have a different effects on the gut. A 2013 study compared the effects of fructose and fructans.

Sixteen healthy volunteers participated in the study. Subjects were given four different solutions: glucose (a well-digested/absorbed sugar) which acted as a control (or placebo); fructan; fructose or fructose with added glucose. After consuming each solution, subjects underwent MRI scans to assess the water content of the small intestine and the gas content of the large intestine.

The study showed that fructose caused an increase in the water content of the small intestine (probably due to osmosis), while fructans increased the gas content of the large intestine. The study highlights that different FODMAPs behave differently, even within the same gut. It also helps us to understand why different FODMAP may contribute to different IBS symptoms. The study suggests that dietitians should tailor a person’s low FODMAP diet to mitigate specific IBS symptoms.

Reference: Murray, K., V. Wilkinson-Smith, C. Hoad, C. Costigan, E. Cox, C. Lam, L. Marciani, P. Gowland and R. C. Spiller (2014). "Differential effects of FODMAPs (fermentable oligo-, di-, mono-saccharides and polyols) on small and large intestinal contents in healthy subjects shown by MRI." Am J Gastroenterol 109(1): 110-119.