Calories: the energy we need

The human body needs energy to carry out all its functions,and this energy is obtained by eating food.

 

Calories are a way of measuring energy.

 

A calorie (cal) is defined as the quantity of calorific energy required to increase the temperature of one gram of water by one degree centigrade.A kilocalorie (kcal) is equal to 1,000 cal.Therefore,1 kcal is the quantity of calorific energy required to increase the temperature of one kilogram of water by one degree centigrade.

 

Even though the calorie is a very commonly-used unit of measurement,the unit used by the International System of Units is the Joule (J),one cal being equal to 4.19 J.

 

The foods we eat contain nutrients,and these are transformed into energy.The amount of energy provided by the different nutrients is calculated in kilocalories.However,in everyday speech in general,the term calories is used to refer to what are,in actual fact,kilocalories.

 

The energy provided by the different nutrients is as follows:

• 1g of protein provides approximately 4 kcal
• 1g of carbohydrate provides approximately 3.75 kcal
• 1g of fat provides approximately 9 kcal

 

These main nutrients also provide other nutrients.There are other elements in food that do not provide energy but are no less important,such as vitamins or mineral salts.

 

The energy required by human beings is obtained from macronutrients and transformed into kilocalories (thousands of calories).In Biology,Medicine and Nutrition the symbol Cal (with a capital C) is still used to denote a kilocalorie (kcal):

 

1 Cal = 1 kcal = 1,000 cal = 4.184 kJ = 4,184 J