Dissecting dietary solutions to IBS


Dear Dietitian,

I have irritable bowel syndrome (IBS) and appreciated your column on a high fiber diet to manage IBS. My symptoms are usually pretty well-controlled, thank goodness. I’ve been reading about the low FODMAP diet, and it seems pretty detailed. Should I try it?



Dear Katie,

The low FODMAP diet was created by a research team at the Monash University in Melbourne, Australia, as a treatment for irritable bowel disease (IBS) (1). As you know, IBS is an intestinal disorder that requires a diagnosis by a physician or other qualified clinician. Sufferers of this condition may experience abdominal pain, flatulence, diarrhea, or constipation.

FODMAP is an acronym that stands for “Fermentable Oligo-, Di-, Mono-saccharides And Polyols. These are short-chain carbohydrates that are not easily absorbed in the small intestine. They draw water into the gut and are broken down by gut bacteria, creating gas in the process. Their digestion can cause abdominal discomfort, bloating, and excess gas. These short-chain carbohydrates are not bad for you. On the contrary, they are found in delicious, nutritious foods like fruits, vegetables, and milk.

When you think of fermented food, you may think of sauerkraut or hard cider. Fermentation is the process by which the body converts a saccharide (sugar) into an alcohol or acid. When we think of sugar, we often think of white sugar (sucrose), but a saccharide is simply some form of glucose or fructose (fruit sugar). The different saccharides in this case just indicate the number of sugar molecules: mono-one, di-two, and oligo-a few.

In the FODMAP diet, oligosaccharides of concern are fructans and galactans. Fructans are found in onions, garlic, and wheat, to name a few foods. Galactans are found in chickpeas, beans, and cabbage (2). The main disaccharide of concern is lactose, found in milk and other dairy products.

Fructose is a monosaccharide. People with IBS may have trouble tolerating fruits with high fructose content, such as watermelon and mangoes. Other problematic foods include honey, agave, and high fructose corn syrup (3).

Polyols are sugar alcohols that occur naturally in some fruits like apples and pears and some vegetables, such as mushrooms and cauliflower (4). Sugar alcohols are also manufactured commercially and are used as sugar substitutes. These include sorbitol, mannitol, xylitol, and maltitol.

The low FODMAP diet has two stages. In the first stage, lasting six to eight weeks, FODMAP foods are removed from the diet. In the second phase, each FODMAP food is added back to the diet. The slow reintroduction of foods makes it possible to identify which ones are causing problems.

As you mention, Katie, your IBS symptoms are under good control, and you are correct in saying this diet is very detailed. Also, keep in mind that, as with any diet, there are risks. While many IBS sufferers have found relief from their symptoms with a low FODMAP diet, risks include unnecessary food restrictions and nutrient deficiencies. If you decide to give it a try, contact a Registered Dietitian Nutritionist for proper instruction.

Until next time, be healthy!

Dear Dietitian


1. Gibson, PR. History of the low FODMAP diet. J Gastorenterol Hepatol. 2017 Mar; 32 Suppl 1:5-7.

2-4. King, Kristi. (2019, August 2). What is the Low FODMAP Diet? Retrieved from URL https://www.eatright.org/health/allergies-and-intolerances/food-intolerances-and-sensitivities/what-is-the-low-fodmap-diet


By Leanne McCrate

Leanne McCrate is an award-winning dietitian based in Missouri. Her mission is to educate the public on sound, evidence-based nutrition. Do you have a nutrition question? Email her at [email protected].

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