When a low FODMAP diet doesn't work. Part 1 of 2

If you responded poorly to a low FODMAP diet, you may be wondering why. We know that a low FODMAP diet is effective in the majority of patients (~60-80%), but this leaves a considerable portion (20-40%) who would not be expected to respond, despite their best efforts complying with the dietary restrictions. If you followed a low FODMAP diet for 2-6 weeks and experienced what you consider an inadequate response, it is worth checking back in with your dietitian to understand why. 

Your dietitian may consider the following:

1. Did you follow the diet properly? By taking a detailed diet history, your dietitian will be able to assess whether you implemented the diet properly, or whether (perhaps unknowingly) you included high FODMAP foods that accounted  for your ongoing symptoms.
2. Have other causes of gastrointestinal symptoms (i.e. other than IBS) been ruled out? This should have occurred before your IBS was diagnosed, but your dietitian may check for alarm features (such as blood in the stool or unexpected weight loss) that may signal the presence of conditions other than IBS and require further investigation.
3. Are your expectations regarding symptom response to a low FODMAP diet realistic? Many patients will find their symptoms improve on a low FODMAP diet, but do not disappear completely. Your dietitian can help you to consider whether the diet has helped to reduce distressing/uncomfortable symptoms to a tolerable level. Your dietitian may also remind you that some degree of symptoms (such as some flatulence) is normal, and a sign of fermentation in your large intestine (a normal, healthy process). In the case of flatulence, your aim would be to reduce troublesome flatulence, but not to achieve zero flatulence.
4. Have you seen a dietitian? A dietitian will consider whether a low FODMAP diet was sufficiently targeted to the underlying cause of your IBS symptoms. A number of pathophysiological abnormalities are thought to account for IBS symptoms including visceral hypersensitivity; enhanced gut-brain communication; altered gastrointestinal motility, and an altered gut microbiome. A low FODMAP diet is thought to primarily help when visceral hypersensitivity is present, but is less helpful when other factors are causing IBS symptoms. 

In next week’s blog we will talk more about working with your health professional to understand the cause of your IBS symptoms, and how doing so may help you to identify therapies that more selectively target the underlying problem.