Carbohydrates are sugars, starches and fibres, and the word ‘carbohydrate’ gives a bit of a clue about their structure. The ‘carbo’ part stands for carbon (C), while the ‘hydrate’ bit refers to water, in the form of hydroxyl groups (OH-). They have the simple formula Cx(H2O)y.
Carbohydrates are divided into four major categories based on their size. The simplest are monosaccharides, or ‘simple sugars’. These single blocks are made up of a small number of carbon
atoms, attached to hydrogen and oxygen atoms, and include glucose, fructose and galactose. Then there are the disaccharides, or ‘double sugars’, like sucrose and lactose. These are made from two simple sugars bonded end-to-end.
Finally, there are the oligosaccharides and the polysaccharides, meaning few and many sugars respectively. Oligosaccharides are chains of between three and six simple sugars, and polysaccharides are even longer, with chains of simple sugars that can be linked together in their thousands.