Calories are the conventional name of the unit expressing the energy value of food, the demand and energy expenditure in human body, which in fact is 1 kilocalorie (1 kcal). 1 kilocalorie is the amount of thermal energy required to heat 1 g of water and 1 degree Celsius. The SI unit of thermal energy is 1 joule (1J), equal to approximately 4,185 kcal.
The energy value is determined by the chemical composition of the food product, by means of the so-called. physiological equivalents. Most often Atwater equivalent is used: ratio for protein 4 kcal / g, for carbohydrates 4kcal / g, and for fat - 9kcal / g.
The energy value carried out with the so-called. "Caloric bomb" is equivalent to the physical energy, amounting to 4.1 kcal per 1 g carbohydrate to 5.65 kcal per 1 g protein, 9.45 kcal per 1 g of fat.
Nutritional value, determines the suitability of a food product for realizing life functions of human, the higher it is - the higher bioavailability and lower quantity for consumption for obtaining the effects.