Together with fat and protein, carbohydrates are one of the main components of nutrition. They are contained in cereal products, vegetables, potatoes and fruit. They are the most important source of energy for humans and therefore 55 to 60% of total energy requirements should come from carbohydrates.
Carbohydrates are classified as:
In the industrial world, diets almost always contain too little carbohydrate (replaced by fat). The "wrong" sort of carbohydrates i.e. sugars dominate instead of starch and fiber.