Cautions for the low FODMAP diet

April 15, 2019

Irritable bowel syndrome (IBS) affects 15% of people worldwide.  If you’re one of them, you are probably well familiar with the fluctuating severity of symptoms and how they affect your life, both at home and at work.  IBS can last a lifetime and has no cure, but there are a number of treatment options to reduce and manage symptoms.  Dietary change is one of those options and can be highly effective.  The trick is finding the diet that works for each person!

One diet for IBS that is being recommended more and more is low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.  It’s known as the low FODMAP diet.  The low FODMAP diet is different from pure elimination diets like a gluten free diet.  On a gluten free diet, all gluten containing foods are avoided.  In the low FODMAP diet, the first phase may feel like an extreme elimination diet.  FODMAP consumption is kept as low as possible for two to six weeks.  That means no lactose containing dairy products, no pistachios, no onions, no garlic, no asparagus, only oyster mushrooms, only green bananas, and no apples, just to name a few of the restrictions of the elimination phase.  The elimination phase is followed by the reintroduction or challenge phase where different classes of foods are reintroduced into the diet in small quantities to see how the gastrointestinal system handles them.  Next comes the final phase, the personalization phase.  In the personalization phase, each individual hones in on how much he/she can tolerate of which foods.  Unfortunately, or perhaps fortunately, the “safe” or tolerated foods will likely change with time.  This means that it is important to occasionally re-challenge with small amount s of poorly tolerated foods because they have moved to the “safe” list.  The opposite is also true though, which may warrant going back through all three phases if the troublesome foods or categories of foods cannot be easily identified.

Not only is it exciting when a food is added to the “safe” list, but it is also helps in eating a diverse diet.  It is important to eat as diverse a diet as your gastrointestinal system can handle.  The long-term effects of staying on a restrict low FODMAP diet are unknown.  Researchers speculate that the consequences include nutritional deficiencies, increased risk of depression and anxiety, and increased risk of eating disorders.  Such a drastic change in diet is likely to affect energy levels and the microbiome too.  The potential effects on the microbiome are compounded by the fact that many prebiotic foods, foods that feed the helpful bacteria in the gut, are high in FODMAPs.  More research is needed in all of these areas, so that we can fully understand the long-term effects of the low FODMAP diet.

If the low FODMAP diet sounds complex and difficult to navigate, you are not alone.  There is specific FODMAP training for dietitians as well as web-based and app-based resources with up-to-date information on FODMAPs.  A lot of the training and resources available focus on the elimination phase of the low FODMAP diet, the first phase.  That was a great place to start, but now we need more research and accompanying resources to help with phases two and three.  There is a small but growing collection of resources for the reintroduction phase, but the personalization phase has not been given much attention yet.

Clinical trials showed that 50 – 80% of people with IBS feel better after reducing FODMAPs in their diet, but many patients are understandably leery of trying the low FODMAP diet because of its restrictive nature and complexity.  To address this issue, researchers are looking into correlations between the different subtypes of IBS and responsiveness to the low FODMAP diet.  So far, the studies suggest that the low FODMAP diet is more effective against IBS-D symptoms, but more studies need to be done with IBS-C to know for sure.  Researchers are also looking for more tests, more accurate tests, to predict if the low FODMAP diet will alleviate a particular individual’s IBS symptoms.  Currently, we know that there is a correlation between a positive fructose breath test and a positive response to the low FODMAP diet.  The same is true of the lactose breath test.  These breath tests are unreliable through, and not everyone with a positive fructose or lactose breath test will feel better on the low FODMAP diet.  Future tests may also involve profiling the gut microbiome and its metabolites.

Without these types of tests to support the low FODMAP diet, it can feel like a huge undertaking without a guarantee of alleviating any symptoms.  To successfully follow the low FODMAP diet, a few skills are necessary.  1) An understanding of how to read ingredient lists on packaged foods.  Sounds easy, but it takes practice to spot the ingredients that are to be avoided.  2) Knowing what questions to ask the server when eating out.  3) Being comfortable cooking mostly from scratch.  There is an increasing number of low FODMAP products available.  Since the prices tend to be double that of the FODMAP containing equivalent, cooking from scratch is often more economical.  To make the low FODMAP diet easier, there are programs like the ETP Food Coaching Program to help individuals build these necessary skills.

The low FODMAP diet has helped many people and will help many many more.  With better tests to predict if the low FODMAP diet will alleviate a person’s IBS symptoms, an understanding of the long-term health effects, tools to help individuals customize the diet in the personalization phase, and support to build the necessary confidence in the kitchen, the low FODMAP diet will be safer and easier.

If you’re interested in more details, check out the following scholarly article.

Mitchell H, Porter J, Gibson PR, Barrett J, Garg M. Review article: implementation of a diet low in FODMAPs for patients with irritable bowel syndrome-directions for future research. Aliment Pharmacol Ther. 2019 Jan;49(2):124-139.

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