Carbohydrates represent the main source of energy necessary for the metabolism, the functioning of the brain and the central nervous system. They are also one of constituent elements of cellular membranes. Because they are quickly digested, carbohydrates release their energy of a significantly faster way than proteins and lipids.
It exist two main sorts of carbohydrates: simple carbohydrates (before called quick-burning sugars) and complex carbohydrates (slow-buring sugars)
Simple carbohydrates are in fruits, honey, in small quantity in most of the plants, in beets, cane sugar, syrups of maple and agave, milk. After transformation, we find them in pastry, croissants and similar products, ice creams, candies, sodas and fruit juice, ready-made meals, ketchup and industrial sauces.
Complex carbohydrates are in cereal (corn, wheat, rice, spelt...), tubers (potatoes, manioc, sweet potato), leguminous plants (peas, beans, lentils, buckwheat), in certain fruits (banana, mango, apple) and in vegetables.
In the West, we consume too many transformed cereal, as bread and pastas. It is recommended to limit our consumption of carbohydrates by favoring those containing many fibers, as fruits and vegetables with low glycemic index.
The glycemic index is the measure of the importance and the speed of the rise of glycemia after absorption of food containing a carbohydrate. A carbohydrate which passes fast in the blood has high glycemic index. The longer time it takes, the more its glycemic index falls. The rate of sugar (glucose) circulating in the blood is regulated by the insulin, hormone made by the pancreas. More food with a high glycemic index we absorb, more our pancreas will have to work. People affected by diabetes have a pancreas which does not produce enough insulin to metabolize glucose and that lead to hyperglycemia.
Food rich in complex carbohydrates (starch and fibers) is desirable and recommended, because it would have an effect in the prevention of certain diseases like cancer of the colon or hyper-cholesterominy. Food rich in simple carbohydrates should be consumed in moderation, to prevent tooth decay and because they contain little or no nourishing elements.