Dietary modification can be beneficial for IBS patients and the FODMAP diet can be an excellent alternative/addition to medications. FODMAP is an acronym derived from “Fermentable, Oligo-, Di-, Mono-saccharides And Polyols.” The idea is that the consumption of some common dietary sugars plays a role in fermentation and in osmotic effects in the bowel as well as visceral hypersensitivity.
Fructose is a monosaccharide that, when combined with glucose, forms sucrose or table sugar. Fructose is the sugar most commonly found in fruits and honey. Many processed foods contain high fructose corn syrup. Fructose may cause GI symptoms when the fructose/sucrose balance is offset. If fructose exceeds the sucrose component, malabsorption of fructose occurs.
Fructans are oligosaccharides typically found in vegetables such as asparagus, artichokes and onions, and in fruit such as apples and wheat. Wheat accounts for much of the fructan intake in the typical American diet. Fructan sensitivity may be why patients that test negative for celiac disease can still have improvement in their symptoms with avoidance of wheat.
Lactose is a disaccharide commonly found in milk products. Irregardless of IBS diagnosis, up to 90 percent of people have some degree of lactose intolerance. Dairy foods low in lactose include hard cheeses, sour cream and butter. These foods are considered safe even following the FODMAP diet. Yogurt that contains lactobacillus may be tolerated as well.
Galactan is a polymer of galactose. Galactans are found in certain vegetables such as legumes. Humans lack an enzyme to digest galactans. Consuming these foods creates an osmotic effect along with fermentation, resulting in gas and bloating.
The final part of the FODMAP diet are the polyols or sugar alcohols (sorbitol, mannitol, and xylitol) which are found naturally in fruits such as watermelon and are used in diabetic sweeteners. While these may be the best choice for glucose control, they can cause adverse GI side effects related to the osmotic effects.
The key to management of IBS is not necessarily more medication or eating more fiber. Many foods high in fiber may also be high in fructose, fructans, or galactans, actually exacerbating IBS symptoms.
Using a FODMAP elimination diet, with slow re-introduction of each food back into the diet can help identify specific food intolerances and aid in avoiding future IBS symptoms. For more information on this, I recommend a book called IBS—Free at Last by Patsy Catsos.
Editors Note: This article first appeared in the Birmingham Medical News blog on May, 9 2013.
Allison Duke Bridges, MD practices in the St. Vincent’s East office of Gastroenterology Associates. Bridges is board certified in Internal Medicine and Gastroenterology.