Fibre, fermentation, FODMAPs and flatus: The ever expanding story of gas bloat


‘I have had IBS for years,  but I am completely confused as to what sort of diet to follow?

It always used to be high fibre; wheat bran and lots of fruit and veg,   Now my consultant tells me I should have a low residue diet, no cereal fibre, little fruit and veg and just rice and chicken, yet many places advocate lots of insoluble fibre as found in porridge oats.  Then there is the fruit issue; some say apple juice is out, yet we are told to eat more fruit – I am OK with bananas, that is about it!  I have ended up eating porridge and eggs, but today I went mad and ate a lamb stew and feel OK at the moment. I am utterly flummoxed. Please help!’

I sympathise with Jane.  It has become so confusing these days and just the worry about whether you are eating the right thing can make it all so much worse. The Bran Wagon has come to a grinding halt by patient studies showing that insoluble fibre such as coarse wheat bran and wholemeal bread can make the symptoms of IBS worse, whereas soluble fibre is kinder to the sensitive gut. But now we have the problem of FODMAPS.  What a dreadful name.  It stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols or to put it in normal speak, those sugars that are not absorbed in the small intestine but are fermented by colonic bacteria generating the gas that causes symptoms of pain and bloating – so best avoided! But hang on a minute, oats contain FODMAPS, so do many fruits and vegetables, including bananas and especially beans and cold cooked potatoes.

So FODMAPS are soluble fibre

So FODMAPS are soluble fibre. They are also prebiotics.  But at least one proprietary probiotic has been shown to reduce bloating. There’s more than one way to stop the bloat, however.  It seems that the poorly absorbed antibiotic Rifamixin, described in an issue of Gut Reaction, might allow you to consume fruit, vegetables, soluble fibre, prebiotics and their associated FODMAPS with impunity by suppressing the bacteria that do the fermentation. But this would drastically alter the colonic ecosystem with what consequences.

Professor Peter Whorwell, who has conducted many  clinical studies on dietary fibre,  would approve of Jane’s mad moment.  In a talk of his that I attended, he told how he advised patients with a flare up of IBS to avoid all types of dietary fibre and fermentable carbohydrate and take a very bland diet. My advice to patients always includes instructions to reduce fatty foods such as meat and dairy and to cut down on coffee, since these foods tend to cause colonic spasm.

You pay your money … and take your choice.  But here’s the rub!  There’s no definitive answer, just evidence, and the evidence changes with time.  Twenty five years ago, gastroenterologists advocated bran for everything. All this has changed!  Was the research flawed?  Is it flawed now?  Research not only directs fashion, it also supports it.  A common sense approach might be understand what effects different components of the diet have on the gut, and to eat what seems to suit you as long as your diet is balanced and contains enough of the essential nutrients to maintain optimal  health. When you are having a bad time and your IBS has flared up, eat a more bland diet, but don’t regard this as a life sentence.  As soon as you’re feeling better reintroduce some of the foods you like and carry on.  Remember, food and mood interact, and if you are upset, your gut will be much more sensitive to what you eat, but this will go when you feel better.  So Jane, I’m glad you enjoyed the lamb stew.  There’s a moral in that. Eat what you like without fear, and your gut may well like it too!

To Read More Join today to access Members' Exclusive Content
Join Login Donate