Low FODMAP Diet Effective for Irritable Bowel Syndrome

Traditional wisdom has been that patients with digestive disorders should consume more fiber, since fiber reduces constipation and keeps food from sitting in the intestines for too long and rotting.  And constipation might mean that certain chemicals, like estrogens are reabsorbed back into the blood stream rather than being excreted, which can raise the risk of breast, endometrial, and ovarian cancer. Insoluble fiber in particular, such as found in wheat bran and other whole grains and also in many vegetables, improves intestinal transit and reduces constipation.  And certainly there are certain patients who will do well with a higher fiber diet that helps the healthy bacteria (probiotics) in the colon to grow. But fiber can also be irritating and certain types of fiber (fermentable fiber) can lead to gas and bloating as some forms of fiber serve as fuel for bacteria in the intestines. The low FODMAP diet is a lower fiber diet that has been shown to be effective as part of a treatment plan for patients with Irritable Bowel Syndrome (IBS) or with Small Intestinal Bacteria Overgrowth (SIBO).

FODMAPs is an acronym that refers to fermentable oligosaccharides, disaccharides, monosaccharides, and polyols,  FODMAPs are a collection of short-chained carbohydrates and sugar alcohols found in a very wide variety of common foods.  The FODMAP category includes fructose, a sugar present in high quantities in honey, apples, and pears; lactose, which exists in milk and other dairy products; and fructo- and galacto-oligosaccharides, contained in wheat, rye, onions, garlic, and legumes. FODMAPs also includes sugar polyols, which occur in some fruits and vegetables and are used as artificial sweeteners like sorbitol and xylitol in gums, sugar free candies, and many other foods.  Keep in mind when trying to sort out which foods have which type of fiber, it can be very confusing, since many foods, such as beans and wheat, contain quite a bit of both soluble and insoluble fiber.

Studies show that the low FODMAP diet is effective for reducing the symptoms of and helping to heal Irritable Bowel Syndrome (IBS) and even Inflammatory Bowel Disorders (IBD) patients, such as those with Crohn’s and Ulcerative Colitis.(1,2)  It is my experience that using this diet for a limited period of time while healing the gut is often a good strategy.  Staying on the FODMAP diet for too long is not healthy, since it stops you from eating too many healthy foods, like cruciferous vegetables.

FODMAPs share three common functional properties.  First, they are poorly absorbed in the small intestine.  They are also rapidly fermented by intestinal bacteria, contributing to excess gas production.  And finally, FODMAPs are small and therefore highly osmotic molecules which, when mal-absorbed, can cause an influx of water into the colon, resulting in diarrhea.  I usually recommend trying the Low FODMAP diet for a 2 to 3 months while trying to eradicate unwanted bacteria in the small intestine or pathogenic bacteria or yeast or parasites in the colon with natural anti-microbials or in some cases, prescription antibiotics (such as Rifaximin) or anti-fungals.


1. Maagaard LAnkersen DVVégh Z, et al. Follow-up of patients with functional bowel symptoms treated with a low FODMAP diet. World J Gastroenterol. 2016 Apr 21; 22(15): 4009-4019.
2. Halmos EP, Power VA, Shepherd SJ, et al.  A Diet Low in FODMAPs Reduces Symptoms of Irritable Bowel Syndrome. Gastroenterology2014;146:67-75.
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