Carbohydrates: what are they and what do they do?
Carbohydrates are the body’s main source of energy. They form the basis of our diet, along with proteins, fats, vitamins, minerals and water.
Carbohydrates provide the whole organism with energy, especially the brain.
There are different types of carbohydrates. Simple carbohydrates (glucose, fructose, sucrose etc.) which have one or two units of sugars and complex carbohydrates (starch, glycogen, inulin, fibre etc.) which are made up of a string of at least ten sugar molecules.
Carbohydrates give some foods their sweet taste (fruit for example). But they are also found in starchy foods such as potatoes, pulses (lentils, peas, chick peas, beans etc.), cereals (pasta, rice, wheat, oats, corn, quinoa, buckwheat, barley, millet, rye etc.).
Carbohydrates, metabolism and blood sugar levels
When we eat, the carbohydrates in the food are broken down by the enzymes in our saliva and our digestive system. Simple carbohydrates (including glucose) are absorbed into the bloodstream via the intestine wall. Glucose is then distributed throughout the body as energy and the surplus is stocked in the liver as glycogen.
When we fast, the glycogen stored in the liver gradually enters the bloodstream to ensure the organism has a constant supply of energy. Blood sugar levels are regulated by two hormones: insulin and glucagon. Insulin is secreted by the pancreas and lowers blood sugar levels by storing glycogen in the liver. Glucagon, also secreted by the pancreas, increases blood sugar levels by releasing glucose into the bloodstream.
A drop in the blood sugar level (hypoglycaemia) can cause fainting, fatigue, dizziness, sweating, trembling, headaches, palpitations or neurological dysfunction.
These symptoms may appear in pancreatic or hepatic pathologies, tumours or following a dose of hypoglycaemic medicine.
On the other hand, a rapid increase in blood sugar levels can lead to a deregulation and have harmful consequences in the long term: weight gain and even obesity, type 2 diabetes, cardiovascular disease (excess carbohydrates having been turned into fat).
The role of carbohydrates
Complex carbohydrates (cereals, pasta, rice, pulses, potatoes, etc.) are digested slowly. Our enzymes gradually break them down into single units. They release energy gradually and and do not spark a rapid increase in blood sugar levels
Simple carbohydrates (sugar, sweets, sugary drinks, fruit, fruit juice etc.) are digested much more rapidly. They provide the organism with a quick boost because they contain nutrients that can be used immediately. However, they cause blood sugar levels to rise rapidly. This can destabilise the metabolism if it happens too often.
Some carbohydrates, i.e. fibre, are not digested at all. They therefore provide no energy but have a positive effect on digestion.