Less is more, even for FODMAPs

October 8, 2018

Two common approaches to treat functional gastrointestinal (GI) disorders like IBS are adding fiber to the diet and restricting certain types of carbohydrates.  If you’ve been to the doctor for your GI symptoms, this advice probably sounds familiar.  Both methods have reduced or alleviated symptoms for countless individuals.  Unfortunately, the right treatment is often times found through a trial and error process.  Does that also sound familiar?  The reason is because the science behind the symptoms is complex.  It depends on many factors like what type of fiber you ate, how much water you drank, what foods you ate at the same time, how much of each food you ate, if there were any probiotics (and which kind) in the food you ate, how long it takes for the food to reach your small intestine, how long it takes for the food to reach your large intestine, and the composition of your gut microbiome.

With all of those contributing factors, it’s difficult to pinpoint the exact issue and determine the best treatment.  The bad news is that it’s going to take researchers and doctors some time to learn how all of these factors work together.  The good news is that there’s something you can do!  You can learn about the different factors that contribute to symptoms and pay attention to how they affect you.  Then, when you go to see your doctor, you’ll have useful insights that he/she can use to narrow in on the best treatment plan for you.

Let’s dive into the details of the types of carbohydrates that may be aggravating your GI system.  They are referred to as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) and are the source of some food intolerances.  Of the FODMAPs, lactose, fructans, and fructose are the most well understood in terms of how they contribute to GI symptoms.

Lactose is broken down by the enzyme lactase into two different sugars, glucose and galactose, which are readily absorbed in the small intestine.  If left as lactose, it causes GI symptoms.  For more about lactose, check out the last week’s ETP blog post.

Fructose is another FODMAP that can trigger food intolerances.  It’s naturally found in foods like honey and apples and also added to processed foods in the form of high fructose corn syrup.  A fructose restricted diet has been shown to reduce GI symptoms in children with fructose malabsorption and is also beneficial for adults who are sensitive to FODMAPs.

Fructans are FODMAPs that are commonly found in wheat, a major part of the Western diet.  Fructans are not digested by enzymes in your stomach and small intestine.  They make it all of the way to the large intestine before being digested by enzymes that are produced by the microbes in your gut.  If the fructan digesting bacteria are not present, fructans may cause some GI upset.

Generally, a restricted diet that eliminates or significantly reduces the amount of FODMAPs consumed will reduce GI symptoms and may be more effective than eliminating a single type of carbohydrate.  In testing out restricted diets to see if they improve your symptoms, it is important to work with a GI specialist and a registered dietician to make sure you are eating a well balanced diet.  The long-term effects of a low FODMAP diet are not yet known.  Research is pointing to changes in the gut microbiome.  There is much more to learn!

If you’re interested in the scientific details of the different types of FODMAPs, check out the following scholarly journal article.

Chumpitazi BP, Shulman RJ. Dietary Carbohydrates and Childhood Functional Abdominal Pain. Ann Nutr Metab. 2016;68 Suppl 1:8-17.


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