Carbohydrates are the world’s single most important food type, contributing between 40 and 75% of the dietary food energy (Calories) in human diets. The main sources of carbohydrates are cereal foods, starchy vegetables, fruit, milk (and milk products) and sugars. There are many different types of sugars, including glucose (also known as dextrose), fructose (fruit sugar), sucrose (table sugar), lactose (milk sugar) and maltose. Sucrose is made up of two components - glucose and fructose. Starch is made up of long chains of glucose units.

During digestion, both starches and sugars are broken down in the same way, into glucose, a simple sugar which can be used by all the cells in the body.

Most organs and muscles in the body prefer glucose as their source of energy, but they can, if forced, use proteins and fats as alternative energy sources. However the brain can only use glucose as its fuel and requires 20 - 30% of the body's daily energy requirement.

Nutrition experts across the world recommend that adults and children above the age of two obtain at least 55% of their daily calories from a variety of carbohydrate sources. Foods containing sugar are a useful way of increasing carbohydrate intake especially in those with high energy requirements, such as athletes and people employed in physically demanding jobs.