Carbohydrates Debunked: What are they and why do we need them?

Classifying Carbohydrates:

Carbohydrates, as we mentioned before, can be split into two groups: simple, and complex. Complex carbohydrates or polysaccharides are made up of strings of simple carbohydrates, monosaccharides.

To make things slightly more confusing, there also exists a subsection of more simple complex carbohydrates known as oligosaccharides. This is the term for a complex carbohydrate that only contains a few links.

Picture a spider’s web – a complex carbohydrate would look like the whole web. A simple carbohydrate would look like one single string, and an oligosaccharide would look like a small collection of strings joined together. Due to their more simple molecular make-up, oligosaccharides are water-soluble and taste sweet. Whereas polysaccharides are tasteless, but they start to taste sweet as these bonds break down, for example, when they are chewed for a long time.

Despite their scientific sounding names, most people are fairly familiar with the major players in each stratum of carbohydrates. Monosaccharides, for example include, among others, glucose, fructose, galactose and also mannose, which is now receiving more and more recognition as an effective alternative remedy for urinary tract infections.

Among the oligosaccharides are old favorites such as Sucrose (table sugar), Lactose (sugar found in the milk of mammals) and the slightly more obscure maltose. Maltose – think Horlicks – arises in the human body during the digestion of starch.


Starch is the most important of the polysaccharides. You can find it in cereal products, potatoes, nuts and legumes and consists of many firmly interconnected glucose molecules. Compared with the distinctly saccharine tastes of mono- and oligosaccharides, starchy foods do not really taste sweet at all. For example, we all know that a sweet potato has more in common with the humble yucca than it does with a mars bar. But why is that? Especially given they are made of the same thing (broadly speaking).

Place a piece of bread in your mouth and leave it there for a few minutes. You will soon notice that it begins to taste incredibly sweet. This is because of the hard work of an enzyme called amylaze. Amylase is one of many enzymes present in our saliva. Its job is to break down the complex structures of carbohydrates into shorter, sweeter sugars. But before we all rush out to patent the potatoes to leave in our new and improved advent calendars – consider that there are a few factors keeping Cadbury’s & Co. in business.

First of which is the time it takes to chew food down to this, quite literal, sweet spot. Leaving sweet potato in your mouth for 20 minutes just to taste the sugar is simply too long for most of us. This leads me nicely to point number 2: Nobody wants to suck a potato. Potatoes are big. They’re big, solid and won’t break down in your mouth due to the inevitable presence of dietary fibre.


Indigestible, inexhaustible, and for some people, simply intolerable: fibre comes from your vegetables. If we were to plot them on a graph, the vegetables that are highest in fibre would show a strong negative correlation for nostalgia. A list of the most fibrous veg reads like a who’s who of our childhood villains (lentils, broccoli, sprouts, etc).

Nefarious intentions aside, fibre also holds the well-deserved honorific as the most complex of all the carbohydrates. So much so that people barely digest fibre because they lack the proper digestive enzymes. Only a few bacterial strains that live in the human colon can use fibre. Those lucky few that are able to break it down are able to turn it into short-chain fatty acids. This in turn serves as an energy source for the other, more common, intestinal bacteria responsible for the regeneration of the intestinal mucosa (vital for the effective functioning of the gut). Hence why you are always hearing about how important fibre is for your digestion.

Sugar alcohols

Last but not least we come to the issue of sugar alcohols. Still counted among the carbohydrates, they taste almost as sweet as sugar. However, sugar alcohols lead to a significantly lower insulin secretion. The sugar alcohols include xylitol, sorbitol and mannitol. While “normal” carbohydrates contain 4.1 kcal per gram, sugar alcohols are generally around 2.4 kcal per gram, which is why they are so often used in diet products, like sweetener.

Calories (in kcal pro 100g)  Glycemic Index
Sorbitol 260 9
Erythritol 20 0
Xylitol 300 13


400 68

Metabolism of carbohydrates:

In order for carbohydrates to be useful to our bodies, they must first be metabolised. This means that they need to be broken down into their simplest forms. This process starts in your mouth. Saliva contains ptyalin, a carbohydrate-digesting enzyme, whose job it is to convert starch into shorter-chain carbohydrates – first to individual maltose molecules, and subsequently into glucose. This is because glucose is small enough to pass through the intestinal mucus into the blood where it is needed to raise the blood sugar level. Once your body notices an increase in blood sugar, it responds by telling the pancreas to produce insulin.

Insulin is a hormone and it controls the distribution of glucose from our blood to our cells. The concentration of sugar in our blood is extremely important and is finely poised. If the levels ever get too low we run the risk of developing life-threatening complications such as hypoglycemia. Should this fall below an acceptable limit, our liver steps in. By breaking down the glycogen we store in our muscles into glucose, the liver ensures that balance is restored.  During extended periods of intense hunger, the liver will actually devour bodily protein to produce the glucose that we so desperately need.

Blood sugar is the Nile of the body. A life cradling river of nutrients that supplies the brain, and thus the body as a whole.

Storage of carbohydrates:

When carbohydrates are absorbed into the cells via the blood they are used for energy. If this energy goes unused then our bodies first turn is to the trusty liver. The liver, while remarkable, is also usually pretty full and when there is no space left, it turns to the muscles, which store carbohydrates in the aforementioned form of glycogen. Only when all other options have been exhausted, will the body finally resort to storing up all this energy as fat.