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A chemical compound composed of carbon, hydrogen and oxygen - with the basic formula Cm(HsO)n. Carbohydrates are classified as macronutrients - and as such, known as 'energy foods'.
The simplest carbohydrates are sugars (monosaccharides), such as sucrose, which are soluble compounds, some with a sweet taste. When these basic sugar units are joined in long chains they form polysaccharides, such as starch and glycogen, which often serve as food stores in living organisms; and as such, they form a major energy-providing part of the human diet - fruit, grains and vegetables contain examples of these.
Even more complex carbohydrates are known, including chitin, which is found in the cell walls of fungi and the hard outer skeletons of insects, and cellulose, which makes up the cell walls of plants.
In the human diet, carbohydrates are supplied mainly from plant foods, such as fruits, grains, pulses and vegetables. Sugar is 100% carbohydrate, cornflakes 85%, rice 79%, flour 73%, pasta 70%, oats 61%, bread 47%, potato 20% banana 20% and apple 12% - so you see why pasta is popular with marathon runners! Sugar should be avoided as a long-term energy food, as it quickly raises sugar, and so energy levels, but the body over compensates, and these drop away to be lower than their original state - so lasting energy must come from the complex variety. Sugar, particularly refined white sugar, also has many detrimental effects, ranging from tooth decay and obesity to fatigue, high cholesterol and diabetes.
Carbohydrates yield 4 calories per gram.