The Lowdown on Low FODMAPS For IBS

The Lowdown on Low FODMAPS For IBS

Without doubt the most common gut disorder we see in our GP Surgery in Fulham is Irritable Bowel Syndrome, or IBS. It can be immensely frustrating for patients who suffer from it. People often find that despite trying a multitude of elimination diets, pills and potions, symptoms such as wind, bloating, pain and altered bowel habit intrude on their lives with infuriating unpredictability.

To an extent the unsatisfying response to treatment is a result of doctors not knowing exactly what the cause of IBS is. A number of factors have been implicated. Medical studies have suggested that infection could be a trigger, that over sensitivity of the gut nervous system has a role, that inflammation of the lining of the gut may be involved and that disordered function of the muscle of the bowel may be a factor. The inevitable consequence of these multiple theories is a variety of disappointing treatments for increasingly frustrated patients.

One almost universal aspect of IBS is that patients notice that symptoms are often worsened by certain foods. The idea of altering diet to improve medical problems is always appealing to both doctors and patients. In the past patients would find it difficult to recognise a unifying theme that tied together often seemingly disparate foods such as apples and cows milk which could provoke symptoms. In the 1980s and 1990 researchers noticed that certain sugars such as fructose and sorbitol could cause IBS symptoms. By 2005 Professor Peter Gibson at The Alfred and Monash University in Australia suspected that a group of short-chain carbohydrates were integral in in the development of bowel disease. The group of carbohydrates were given the acronym FODMAPs which stands for fermentable Oligosaccharides, Disaccharides, Monosacchairdes And Polyols.

These short-chain carbohydrates are thought to cause symptoms in IBS because they are poorly absorbed in our guts and are quickly fermented. Given that the process of fermentation produces both acid and gas it is ideally a process that would occur before we put the food in our mouths. The rapid production of gas likely leads to bloating, abdominal discomfort and may also have a laxative effect.

An early study into the effectiveness of reducing consumption of FODMAPs showed promise for patients with IBS. In this study of 66 people there was good adherence to the dietary modifications and an impressive reduction in abdominal symptoms in three quarters of patients who undertook the diet. A limitation of this study was that it was retrospective. Patients were asked at the end of completing the diet whether it had helped symptoms. This introduces the possibility of recall bias where the participants when contacted about the diet are biased towards overstating its’ effectiveness. It is also subject to placebo effect. As there was not placebo control group in this study patients are more likely to state that the intervention had a positive effect. Placebo effect has been found to be very marked in patients suffering from IBS. Because of these limitations the same group of researchers undertook a randomised placebo controlled trial. Patients who had seen improvements in a low FODMAPs diet were then given a controlled dose of FODMAPs or placebo at meals. The researchers found that the re-introduction of FODMAPs resulted in a worsening of IBS symptoms in the study participants.

In the UK researchers decided to evaluate how the low FODMAPs diet compared to the standard dietary advice. The study lasted three weeks and was a high quality randomised control trial. Almost 70% of patients had “adequate symptom control” on the low FODMAPs diet. In terms of medical interventions, this is pretty good. Interestingly symptoms actually got worse in the standard advice group. The study was limited by the fact that it was carried out under the supervision of a dietician who had many years of experience in the low FODMAPs diet. The effect of an experienced, enthusiastic expert on the low FODMAPs diet will undoubtedly have had some impact on the results. Obviously plenty of people will not want to wait to see a dietician before starting a potentially beneficial diet.

More recently, a study in Denmark investigated low FODMAPs in 123, mainly young female, patients with IBS. This study again showed that low FODMAPs was helpful in reducing IBS symptoms but when the results are examined closely it is evident that the most significant improvement was only in patients who tended to have symptoms of loose bowel motions.

IBS is a condition with a multitude of potential triggers and numerous exacerbating factors. Diet is one, albeit very important, aspect of the management. It is important that if you think you have IBS that you have seen a good doctor to confirm the diagnosis and that other potential serious causes of similar symptoms have been excluded, or at the very least, deemed highly unlikely. Many patients do seem to benefit from a low FODMAPs diet, particularly if they tend to get loose bowel motions. Stanford University have produced a very helpful extensive guide to the foods to enjoy and avoid on the diet. The original research group at Monash University have also produced an excellent app to help explain and guide people through the diet.

Dr Hugh Coyne

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