Friday, 8 April 2016

Research update: FODMAPs alter symptoms and the metabolome of patients with IBS: A randomised controlled trial in Canada

By Marina Iacovou (Accredited Practising Dietitian and PhD Candidate)

The evidence supporting the use of a low-FODMAP diet to reduce symptoms of IBS is gaining momentum around the world.  Last month an article was published by the Journal of Neurogastroenterology of a single-blinded, randomised controlled study, conducted at a teaching hospital – Queens University, Kingston General Hospital, in Ontario, Canada 1.

The study found that 72% of IBS patients responded to the low FODMAP diet, they had a marked decrease in abdominal pain, and tended to have less abdominal distension. The study also provided a high FODMAP diet to a separate group of IBS patients, who reported having significantly more days of abdominal pain, but overall their IBS symptoms were not significantly different to that of their usual diet.

Evidence is also growing that the low FODMAP diet has effects on the gut microbiota. This latest study found that participants following a low FODMAP diet had an increase in the richness and diversity of a bacterium called Actinobacteria, and the study participants following a high FODMAP diet, the bacteria family Bifidobacteriaceae and Lachnospiraceae increased.

However, it still remains unclear what effects these changes in the gut microbiota have in the longer-term. This is why the low-FODMAP dietis not recommended for life, and the re-introduction of higher FODMAP-containing foods is recommended in quantities that are well-tolerated. 

An interesting observation made during this study, was that in a sub-group of patients changes were found in the metabolites measured in urine samples – histamine, p-hydroxybenzoic acid and azelaic acid. These metabolites can be found in food and some may be the result of gut bacterial action.  In particular, in a subset of patients histamine levels were significantly reduced in the low FODMAP group, and unchanged in the high FODMAP group. It is already known that in patients with IBS, histamine levels in the gut mucosa are increased2.  

However, these findings pave the way for larger studies, to understand if the collection of urine samples can be a practical means of testing patients with IBS.  It also highlights that multiple pathways can lead to symptoms of IBS. Therefore, it is very important to seek the advice of a medical specialist anda dietitian, to ensure a proper diagnosis and correct management of your symptoms.  

If the low FODMAP diet doesn’t work for you, there are other alternative treatments for IBS

1)      Keith McIntosh, David E Reed, Theresa Schneider, Frances Dang, Ammar H Keshteli, Giada De Palma, Karen Madsen, Premysl Bercik, Stephen Vanner. FODMAPs alter symptoms and the metabolome of patients with IBS: a randomised controlled trial. Gut 2016;0:1-11. Doi:10.1136?gutjnl-2015-311339

2)       Barbara G, Cremon C, Carini G, Bellacosa L, Zecchi L, De Giorgio R, Corinaldesi R, Stanghellini V. The immune system in irritable bowel syndrome. J Neurogastroenterol Motil 2011;17:349–59.

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