Energy equivalents, calories, values – what they are?
What does energy equivalent mean, energy value, and what does calorie mean?? Many of us wonder what are the basic concepts that we encounter every day in websites and blogs about healthy eating, such as. calories. To put it simply one A calorie (inch) is the amount of heat needed to heat 1 gram of chemically pure water by one degree Celsius at a pressure of one atmosphere. The basic unit of energy in the international SI system is Jul (Joule) – [J]. It is worth to have a look at the diagram below:
1 kilocalorie [kcal] = 1000 [cal]
1 kilojoule [kJ] = 1000 [J]
1 [kcal] = 4.184 [kJ]
The energy value of food, which determines how valuable a given food is for us, is determined with the help of the so-called. energy equivalents: physical and physiological. We often come across this concept in the field of dietetics, but not many of us think about what it really means.
Physical energy equivalent
When we talk about physical energy equivalent, we mean the amount of energy that is released when burning one gram of protein, one gram of fat, one gram of carbohydrate under conditions of, let’s call it, extracorporeal, in the so-called. calorimetric bomb. As a result of burning all organic substances contained in food (in humans, the combustion process does not take place completely), we get the following physical equivalents:
for 1 g of protein – 5.65 [kcal]
for 1 g fat – 9.45 [kcal]
for 1 g carbohydrate – 4.1 [kcal]
Physiological energy equivalent
The physiological energy equivalent is the amount of energy that the human body releases from one gram of protein, one gram of fat, one gram of carbohydrates.
For the calculation the following is used:
Okay, so we already know what energy equivalents are, but now let’s consider, How to calculate how valuable food is, which we supply to our body. With this knowledge, we will be able to successfully prepare such meals that will be really nutritious for us! For this purpose, we use two equivalents: Atwater and Rubner, whose description you will find below.
Atwater equivalent, i.e. one that relates to net energy, i.e. energy assimilated by the human body, obtained from food after taking into account digestibility and assimilability. And so:
for 1 [g] protein – 4.0 [kcal]
for 1 [g] fat – 9,0 [kcal]
for 1 [g] carbohydrate – 4.0 [kcal]
So as we can see according to Atwater’s equivalence, 1 gram of protein is about 4 calories. Similarly with 1 gram of carbohydrates, and 1 gram of fat is as much as 9 calories. So it is certainly worth paying attention to what we eat.
Another equivalent that is used in calculations is the Rubner equivalent. This is nothing else but a notation that relates to gross energy. Thus:
for 1 [g] protein – 4,1 [kcal]
for 1 [g] of fat – 9.3 [kcal]
for 1 [g] carbohydrate – 4.1 [kcal]
Furthermore, the following ingredients are determined for counting the energy value of a meal:
for 1 [g] ethyl alcohol – 7 [kcal]
for 1 [g] organic acids – 3 [kcal]
for 1 [g] polyols – 2.4 [kcal]
As you can see, the differences between Rubner’s and Atwater’s equivalents are slight, but nevertheless present. For example, 1 gram of protein is, as we mentioned earlier, 4 calories in Atwater’s case and 4.1 calories in Rubner’s equivalent. These differences are due to the way calories are calculated, in the case of Rubner’s methodology we calculate gross energy, i.e. the total energy delivered to the body without taking into account the process of combustion and excretion.
As you can see by knowing energy equivalents we can provide our body with an adequate diet to provide as many calories as we really need.