Carbohydrate

Carbohydrate, any of a group of chemical compounds—including sugars, starches, and cellulose—containing carbon, hydrogen, and oxygen only, with the ratio of hydrogen to oxygen atoms usually 2:1. Carbohydrates provide the chief source of energy in most diets; about 50% of the total calories in the diet of a prosperous industrial community come from carbohydrates. In a poor agricultural community, living largely on cereals, the proportion is higher and may be as much as 85%. The chief dietary carbohydrate is starch, which is present in all cereal grains, roots, and tubers.