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

Even though monosaccharides are what the fourth letter of the word FODMAP stands for, it’s important to start the explanation of the low-FODMAP diet here, because monosaccharides are the most simple short-chain carbohydrates that irritate the gut and in order to understand the more complicated short-chain carbohydrates one needs to be able to fully understand the science behind monosaccharides.

Monosaccharides form the building blocks, from which all carbohydrates are made. Monosaccharides are simple sugars which are usually:

 · Colorless;
· Water-soluble;
· Solid crystals.

Contrary to what their name – sugars – might suggest, not all monosaccharides have a sweet taste.

There are a variety of monosaccharides, including:

· Glucose (also known as dextrose);
· Fructose (also known as levulose);
· Galactose.

Disaccharides

When two monosaccharides are joined together their name changes. It becomes a disaccharide.

Disaccharides are the type of short chain carbohydrates for which the third letter of the word FODMAP stands.

We’ll get to disaccharides in another blogpost, since lactose is a disaccharide, but let’s first get familiar with monosaccharides.

The Science

The monosaccharide glucose (arguably) plays the most important role in the human metabolic system.

In order to use food as fuel, the body needs to breaks down any and all foods into smaller pieces.

Some foods turn into amino or fatty acids, but most carbohydrates are broken down into the previously mentioned monosaccharide: glucose.

But why do monosaccharides cause so many symptoms?

Monosaccharides are one of the four categories of short chain carbohydrates which that may cause symptoms in people with Irritable Bowel Syndrome (IBS) and / or Small Intestinal Bacterial Overgrowth (SIBO). These symptoms can include abdominal pain, bloating, constipation, diarrhea and nausea.

But the question remains, why do these short chain carbohydrates cause so many problems? Well, the first letter of the term FODMAP stands for fermentation and that chemical process of fermentation is exactly what causes your symptoms. So what exactly does fermentation do?

‘You may have heard of fermentation in connection with yeast. Yeast performs fermentation to produce energy by converting sugar into alcohol and carbon dioxide. Fermentation turns fruit juices into wine and grain mash into beer or whiskey.

The carbon dioxide produced by fermentation makes the bubbles in beer and some kinds of wine, and causes bread to rise.

Bacteria in our colon extract energy by fermenting carbohydrates, but the fermentation process also yields gasses. In the case of glucose [the monosaccharide into which fructose needs to be broken down, in order to digest it] the fermentation process leads to hydrogen, carbon dioxide and methane.

In addition to accumulating gasses, polyols, monosaccharides, disaccharides and small undigested remnants of oligosaccharides cause what is called an osmotic effect.’ 1

Osmosis explained

Osmosis refers to the movement of water molecules from a solution with many water molecules, to a solution with little water molecules.

In the digestive system, osmosis occurs as the result of compounds like (1) salt, (2) poorly digested or (3) completely undigested remnants of FODMAP’s.

These three compounds all attract water like a magnet, resulting in a more watery stool than it would have been without the occurrence of osmosis.

This osmotic reaction leads to bloating, gas, diarrhea and pain. Thus osmosis – also known as an osmotic reaction – is an important process to understand, to gain a better understanding of where your symptoms come from. That being said, osmosis is quite shit – literally and figuratively – to experience.