Carbohydrates

Carbohydrates are a main dietary component and considered a macronutrient (1). The liver breaks down carbohydrates into glucose (blood sugar) which contributes energy to the body, particularly the brain and the nervous system (2). Carbohydrates are classified in two groups, simple, which are sugars, and complex, which are starches and fibre (2). Complex carbohydrates include whole grain breads and cereals, starchy vegetables and legumes. Simple carbohydrates naturally contain vitamins and minerals and include fruits, vegetables, milk and milk products. Simple carbohydrates are also found in refined sugars (2). The healthiest diet obtains carbohydrates, vitamins, and other nutrients in as natural a form as possible (example: from fruit instead of table sugar) (2).

Linus Pauling http://lpi.oregonstate.edu/infocenter/glossary.html#carbohydrate
U.S. National Library and the National Institute of Health
http://www.nlm.nih.gov/medlineplus/ency/article/002469.htm#Definition