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, which seems pretty detailed. Should I try it?

Katie

Dear Katie,

The low FODMAP diet was created by a research team at 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 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. 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.

In the FODMAP diet, the 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, which is 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 certain 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. FODMAP foods are removed from the diet in the first stage, lasting six to eight weeks. 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 mentioned, Katie, your IBS symptoms are under good control, and you are correct in saying this diet is very detailed. Also, remember 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 try it, contact a Registered Dietitian Nutritionist for proper instruction. 

Until next time, be healthy!

Dear Dietitian

References

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