Calories and Food
The usefulness of a food for the body is proportional to the amount of energy that can release when burned. Therefore, the energy value is measured in calories. A calorie is the amount of heat required to raise one degree temperature of one gram of water. As its value is very small, in physiology is taken as unit the kilocalorie. So when we talk about calories, we always refer to the kilocalorie, and when we do the caloric value of food, we will refer to its ability to produce or deliver energy.
The caloric value of food is different, so, one gram of sugar and one gram of protein developed to burn four calories, while one gram of fat produces nine calories, which is why we say that the caloric value of sugars and protein is four, while the fat is nine.
Vitamins and minerals, and trace elements, water and fiber, does not contribute calories.
At this point a question arises. We calculate, as we said, the utility of food as energy may be released, but while part of the diet is used to produce energy, another is used to rebuild the structures of the body (for serving, plastic , non-energy). It might seem that there is a contradiction between the first and the second claim, but in fact only apparent.
The body, to have need for some amount of daily energy to live, burning an appropriate proportion of substances that constitute the “sea” rich molecules that react with each other and are called intracellular fluid.
We have to replenish every day in this “sea” as many molecules with the same energy capacity, so that the body is kept intact. Since some energy has been spent by destroying a number of molecules, we must rebuild the body’s energy assets, providing adequate amounts of molecules, which is calculated by the energy that can liberate, ie according to their caloric value .
The transformation of food by humans do not result in any change in basic nutrients (proteins, fats, carbohydrates or carbohydrates), which means that a gallon of milk or boiled water preserved contains the same amount of protein, fat and carbohydrates that a fresh milk. However, there is a fundamental difference between them that affects their vital substances contained in the more intense the changes to the structure undergoes a meal, the greater the threat to remove, destroy, damage or destabilizing vital substances contains. So to have a scale for comparing the biological value of food, not only should be taken into account in their nutrient content but also the vital.