Concept of carbohydrates
Carbohydrates
The carbohydrates are the compounds which provide energy to living cells. They are compounds of carbon, hydrogen and oxygen with a ratio of two hydrogen’s for every oxygen atom. The carbohydrates we use as foods have their origin in the photosynthesis of plants. They take the form of sugars, starches, and cellulose.
The name carbohydrate means "watered carbon" or carbon with attached water molecules. Many carbohydrates have empirical formula which would imply about equal numbers of carbon and water molecules. Carbohydrates are so named because the structural formula is typically (CH2O) n, where n is an integer such as 5 (C5H10O5), 6 (C6H12O6), etc. Although this formula might suggest that carbon atoms are joined to water, the actual molecules are more complicated.
For example, the glucose formula C6H12O6 suggest six carbon atoms and six water molecules. Carbohydrates, which include the sugars and polysaccharides, have many important functions in biological systems.

Like most classes of biological molecules, carbohydrates occur as both monomers and polymers. Small carbohydrates are called sugars, which commonly include monosaccharaides (single sugars) and some disaccharides (two sugars linked together). Larger carbohydrates are called polysaccharides (many sugars linked together).

Functions of carbohydrates include:

• serving as precursors for building many polymers

• storing short-term energy

• providing structural building materials

• serving as molecular "tags" to allow recognition of specific cells and molecules

Carbohydrates are classified as simple or complex. The classification depends on the chemical structure of the food, and how quickly the sugar is digested and absorbed. Simple carbohydrates have one (single) or two (double) sugars. Complex carbohydrates have three or more sugars.
Examples of single sugars from foods include:
Fructose (found in fruits)
Galactose (found in milk products)
Double sugars include:
Lactose (found in dairy)
Maltose (found in certain vegetables and in beer)
Sucrose (table sugar)
Honey is also a double sugar. But unlike table sugar, it contains a small amount of vitamins and minerals. (Note: Honey should not be given to children younger than 1 year old.)
Complex carbohydrates, often referred to as "starchy" foods, include:
Legumes
Starchy vegetables
Whole-grain breads and cereals

Simple carbohydrates that contain vitamins and minerals occur naturally in:
Fruits
Milk and milk products
Vegetables
Simple carbohydrates are also found in processed and refined sugars such as:
Candy
Regular (non diet) carbonated beverages, such as soda
Syrups
Table sugar

All food that you eat turns to sugar in your body. Carbohydrate-containing foods alter your sugar levels more than any other type of food. Carbohydrates are found in starchy or sugary foods, such as bread, rice, pasta, cereal, potatoes, peas, corn, fruit, fruit juice, milk, yogurt, cookies, candy, soda, and other sweets.

Refined sugars provide calories, but lack vitamins, minerals, and fiber. Such simple sugars are often called "empty calories" and can lead to weight gain.
Also, many refined foods, such as white flour, sugar, and white rice, lack B vitamins and other important nutrients unless they are marked "enriched." It is healthiest to get carbohydrates, vitamins, and other nutrients in as natural a form as possible -- for example, from fruit instead of table sugar.

Side Effects
Getting too many carbohydrates can lead to an increase in total calories, causing obesity.
Not getting enough carbohydrates can cause a lack of calories (malnutrition), or excessive intake of fats to make up the calories.
Recommendations
Most people should get between 40% and 60% of total calories from carbohydrates, preferably from complex carbohydrates (starches) and natural sugars. Complex carbohydrates