Carbohydrates are one of the central nutrients to living organisms. They are a type of macronutrient found in both natural and processed food. Important carbohydrate sources in the diet are bread, potatoes, rice, pasta. The term is most common in biochemistry, where it is a synonym of saccharide. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
The most common building block of carbohydrates is glucose. Carbohydrates perform numerous roles in living organisms. Some carbohydrates, such as sugars and starch, are easily digested and absorbed. Other, more complex carbohydrates, also known as dietary fibres, are less well absorbed and end up in the large intestine, as food for our gut microbiota. In our bodies, glucose is an important source of energy, and polysaccharides (in the form of glycogen) serve for the storage of energy. Besides, carbohydrates play key roles in many other processes in our body.