The term FODMAP was coined to give a name to the 4 categories of short-chain carbohydrates which all irritate the gut, one way or another.

In order to properly understand the FODMAP diet, the ways it works and why not sticking to the diet causes so many symptoms, we need to begin by understanding what the various parts of the word FODMAP mean. Today we’re taking a closer look at the second to last category: monosaccharides.

Monosaccharides

In order to understand how disaccharides irritates the gut, we need to take a closer look at what monosaccharides are and how the human body digests them. I highly recommend reading our article about monosaccharides. But in case you missed it: monosaccharides are the basic building blocks from which all carbohydrates are built.

Disaccharides

When two monosaccharides are bonded to one another, by a so-called glycosidic linkage, they form a disaccharide. Disaccharides are the type of short chain carbohydrates for which the third letter of the word FODMAP stands. There are a variety of different disaccharides, including:

● Sucrose;

● Lactose;

● Maltose.

‘The joining of monosaccharides into a double sugar, called a disaccharide, happens by a condensation reaction, which involves the elimination of a water molecule. […]’ 1

Disaccharidases

Breaking apart a double sugar into its two monosaccharides is accomplished [by a process called] hydrolysis with the help of a type of enzyme called a disaccharidase. Each disaccharide is broken down with the help of a corresponding disaccharidase’ 1:

Sucrase is needed to break down sucrose;

Lactase is needed to break down lactose;

Maltase is needed breaking down maltose.

Lactose is one of the six subcategories of short-chain carbohydrates that need to be avoided on a low-FODMAP diet.

Lactose intolerance is the result of a lack of lactase enzymes in the small intestines. This results in the inability to break down lactose into glucose and galactose.

Just like with undigested fructose, undigested lactose gets transported into the large intestine. There it gets fermented by the gut bacteria, also referred to as colonic flora. During this process of fermentation the colonic flora releases a combination of hydrogen, carbon dioxide and methane, leading to symptoms like bloating, diarrhea, flatulence and gastrointestinal pain.

Symptoms typically start thirty minutes to two hours after eating or drinking milk-based food. Their severity typically depends on the amount a person eats or drinks. For more information about lactose, click here.