Treating SIBO: What is the Low FODMAP Diet?
For a primer on SIBO (Small Intestinal Bacterial Overgrowth), start here.
Modifying the diet is one of the most critical components of effective SIBO treatment, and there is a simple reason for it: bacteria are living organisms and they need to eat to survive. When we have an overgrowth of bacteria, we want to starve them of their food sources. Luckily, we have a good amount of control over what they eat, because they eat what we eat. There are a few different options when it comes to special diets for SIBO, but they are all centered around this basic principle– the principle of the low FODMAP diet, our focus for this post.
The “F” in “FODMAP” stands for “Fermentable”. This defines the essential principle of the diet: FODMAP foods (to be avoided) are not completely absorbed by our bodies, and are fermented in the gut. Once fermented, they act as food– as fuel— for the bacteria running rampant in the small intestine.
The “ODMAP” portion of the acronym refers to the four groups of fermentable carbohydrates that are to be eliminated during the diet: Oligosaccharides, Disaccharides, Monosaccharides, (And) Polyols. Knowing what to eat and what to avoid on a low-FODMAP diet is not necessarily intuitive, as a number of foods in the “avoid” category are generally regarded as healthy foods (and they are, if you don’t have a specific digestive concern like SIBO). Here we provide an overview of some common foods to cut out, but we recommend keeping on hand a more comprehensive food guide if you are taking this diet on.
High FODMAP Foods
–Fructose: Avoid ALL processed sugars; honey; maple syrup; agave; apples; cherries; pears; mangoes
-Lactose: This is the sugar found in cow, goat, and sheep’s milk, therefore, you will want to avoid most dairy products– unless they are lactose-free.
–Fructans: This one is a bit trickier. Fructans are a type of carbohydrate found in a number of fruits, vegetables, and grains, in varying levels. Some common foods high in fructans are gluten & wheat products; barley; rye; broccoli; asparagus; grapefruit; plums; watermelon; garlic; onions; and leeks.
-Galactans: Galactans (along with fructans) are another “oligosaccharide” (carbohydrates consisting of multiple sugars). Many legumes are high in galactans, including chickpeas, lentils, kidney beans, and soy. Some vegetables, including brussels sprouts and cabbage, are also high in galactans.
-Polyols: Polyols, also known as sugar alcohols, are often found in low-calorie/sugar-free food products, and in some medications. This is one that you may need to be checking ingredient labels for. Common polyols include mannitol, sorbitol, and xylitol.
Following a low FODMAP diet can, quickly, lead to an improvement in digestive symptoms caused by fermentation, such as excess gas. The longer-term goals of the diet are to heal and repair the intestinal lining, and of course, reduce the overgrowth.
It is also critical that the foods we do eat during this time provide us with an abundance of the nutrients that we haven’t been properly absorbing. It’s important to eat a good variety of allowed foods, which include leafy greens, carrots, cucumbers, tomatoes, blueberries, strawberries, pineapple, wild-caught tuna and salmon, almond milk, coconut milk, quinoa, squash, zucchini, bell pepper, tofu, poultry, and eggs.
There is a third important component of eating properly to conquer SIBO: reducing intake of inflammatory foods (many of these are already taken care of with the FODMAP index, however, for your reference: common dietary sources of inflammation include processed sugars, refined flour, dairy products, saturated fats, and grain-fed meats). Inflammatory foods are hard on the whole system starting with the digestive lining, and they decrease the production of stomach acid. Without adequate amounts of stomach acid, we are left with more undigested food particles for bacteria to feed on.
There has been a good deal of promising research on the low FODMAP diet for IBS (Irritable Bowel Syndrome), including one double-blind crossover trial which found that digestive symptoms significantly improved for all participants while following the diet (1). With SIBO thought to be the cause of IBS in many sufferers, and as many as 84% of IBS patients found to have SIBO (2), it stands to reason that these benefits would carry over, and many practitioners and patients have found this to be the case.
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