Carbohydrates (mainly sugars) occur in pure form in our food and are used as binders or sweeteners. They can also be added to industrially prepared or home-made dishes as a binder, preservative, sweetener or bulking agent.

A distinction is made between added sugars and sugars naturally present in food. However, their chemical structure is virtually the same. If "sugar" is mentioned in the list of ingredients of a foodstuff, this indicates the addition of sugar or sucrose.

In healthy eating, a distinction is often made between refined and unrefined carbohydrates. The unrefined carbohydrates contain more dietary fibre. Examples: brown rice, nuts, seeds, legumes, etc.

Functions of carbohydrates

As a carbohydrate, glucose is the main source of energy for our bodies. When burned, 1 g of carbohydrates provides 4 kcal or 17 kJ of energy.

Glycogen serves as an energy reserve for humans and animals and is stored in the liver and muscles.

Galactose is important for brain development and is part of the galactolipids in the brain.

Inulin and oligofructose act as prebiotics.

Dietary fibres play an important role in the gastrointestinal system. Their function depends on the nature and structure of the dietary fibre:

  • In the mouth, they stimulate the chewing function and increase the secretion of juices.
  • In the stomach, they increase the feeling of satiety. Insoluble dietary fibres increase the volume by binding with water; soluble dietary fibres slow down gastric emptying.
  • In the small intestine, soluble fibres slow down the passage times and ensure the gradual absorption of simple carbohydrates.
  • In the large intestine, fermentable fibres form short-chain fatty acids, improve the intestinal flora and lower the pH. In addition, they increase peristalsis (movements of the intestine to propel the contents) and reduce pressure in the colon.
  • In the rectum, they ensure that the stool is excreted from the body more quickly.

Connection to health

If too few carbohydrates are ingested, the body will start to use amino acids, which results in the breakdown of tissue proteins. With prolonged fasting, the body switches to burning ketones.

Ketones are produced naturally by our liver when we run out of carbohydrates and start burning fat.

Consuming too many carbohydrates leads to obesity and tooth decay.

Over-consumption of added sugars can affect the risk of type 2 diabetes and jeopardise the supply of essential micronutrients (vitamins, minerals and trace elements).

Metabolism of carbohydrates

Glucose circulates in the bloodstream and determines the blood sugar level. During and immediately after the meal, the blood sugar level rises. Afterwards, it falls back to its initial values. If glucose is not absorbed sufficiently by the cells, hyperglycaemia occurs and the excess is excreted via the kidneys.

Fasting induces a state of hypoglycaemia where the blood sugar values are lower.

The pancreas secretes insulin. This substance ensures that glucose is absorbed by the cells. This causes the blood sugar level to return to its initial values.

Glucagon, the counterpart of insulin, has an increasing effect on the blood sugar level in hypoglycaemia.

Glycogen is stored as a reserve in the liver and in the muscles. Glycogen from the liver serves mainly to maintain the blood sugar level. Glycogen from the muscles mainly supplies energy.


Carbohydrates are the most important fuel for our body. With a healthy diet, it is of course important to pay attention to:

  • The amount of carbohydrates we consume (in relation to the amount of calories we burn)
  • The proportions of the different types of carbohydrates we consume (simple or complex, natural or added, etc.)

If you have health problems (e.g. diabetes), it is best to seek guidance from a doctor and/or a qualified nutritionist.

- Translated from Dutch by Tamara Swalef -