The quantitatively by far largest component of human nutrition besides fat and protein the carbohydrates. The various cereals (e.g. oats, rice, maize, wheat, millet, rye) – as well as products made from them, such as pasta, bread and other bakery products – form the basis of our diet due to their high carbohydrate content and are therefore also called staple foods.
But also pulses like beans, peas and lentils, as well as potatoes are rich in carbohydrates. Carbohydrates are found in various forms in fauna and flora. We know many of these forms, but not as carbohydrates. Or did you know that the chitin shell of insects is a form of carbohydrate?
A small selection of carbohydrate forms
carbohydrates occur in various forms. Here is a list of the most common:
- Glucose (glucose or more rarely dextrose)
- Fructose (fructose)
- Sucrose (beet sugar or cane sugar)
- Lactose (lactose)
- lactulose (synthetically modified lactose).
- Starch (food ingredient)
- cellulose (supporting substance in the plant kingdom). Indigestible for humans. Can be used by ruminants such as cattle, sheep and goats, as these contain bacteria in their stomachs (rumen) that help digest cellulose.
- Glycogen (energy storage in muscles and liver)
- Chitin (supporting substance of the exoskeleton of arthropods and insects)
Digestion and utilization of Carbohydrates
The universal energy carrier and transporter of our body is adenosine triphosphate (ATP), which drives all biological processes, including muscle contraction, and is involved in almost all energy-consuming processes as an energy supplier. ATP is only present in low concentrations in our cells and must be replenished by aerobic and anaerobic degradation of our food (fat, carbohydrates, proteins).
Carbohydrates are the main source of energy, as they can be used relatively quickly in contrast to fats. The most important carbohydrate for our body is glucose. The acute energy supply of our body is essentially guaranteed by the glucose dissolved in the blood. Their concentration in the blood, the so-called blood sugar level, is kept within narrow limits.
In the cells of the various organs, glucose provides energy for muscle work, for example, through metabolism (aerobic via the citric acid cycle in the mitochondria and anaerobic via glycolysis in the cytoplasm). For more information see “The cell – structure and function”.
Carbohydrates are present in food in more or less long chains. These must first be broken down into glucose in the digestive tract. If starchy foods such as bread or potatoes are eaten, the digestive enzymes break down the carbohydrate chains of the starch into smaller and smaller individual fragments down to glucose.
Depending on the length of the carbohydrate chains, this happens at different speeds. The individual glucose molecules then gradually enter the bloodstream. The faster glucose is released in the digestive tract, the faster the blood sugar level rises.
When it is absorbed in the form of sugar, i.e. directly as glucose, the blood sugar level rises very quickly. We can make use of this effect in endurance sports. During the physical and/or mental activity, the body is quickly supplied with energy, e.g. through a sugary drink.
If the supply of glucose to the tissues is greater than their consumption, the excess is first stored in the liver and skeletal muscles. This means that about 200 grams of glucose can be stored in the liver and about 300 grams in the skeletal muscles. Once these glucose stores are full, the remaining glucose is converted into fat and stored as depot fat.
Fats have a higher energy content per mass than carbohydrates (1 gram of fat has 9.3 Kcal, 1 gram of carbohydrate 4.1 Kcal). They are therefore more space-saving than carbohydrates for long-term energy storage and provide better thermal insulation of the body.
Carbohydrates in sports
Contrary to popular belief, the fat depots are constantly accessed for energy production and not only when the glycogen storage in the muscle is reduced. In fact, the proportion of fat burning for energy production is highest at rest with approx. 70 %!
It is also wrong that fat burning only starts after approx. 30 minutes of endurance training. In fact, the adenosine triphosphate (ATP) for intensive muscle work is constantly supplied by several energy sources, including fat.
The more intense the effort, the more the anaerobic portions increase and the aerobic portions decrease. As a result, the relative (= percentage) percentage of fat burning decreases with an increased pulse rate, but the absolute amount of fat used does increase as the power conversion also increases.
In addition, there is a glucose deficiency in the blood after training. The fats are therefore burned after the training in order to refill the empty energy stores.
If, however, carbohydrates are supplied to the body directly after a workout, this effect does not occur. If a lot of glucose is burned during training, the more fat is burned during the recovery phase. With increasing training the muscle mass increases, the oxygen intake improves and the basal metabolic rate increases.
This post is also available in: German