In fact it survive when the body is able to carry out many chemical reactions due to a few raw materials for that to stay alive, but of course between surviving and being in good shape an abyss far. The agency extract from the foods we eat chemicals it needs to function properly and to recover from daily activities and to regenerate its own structures, not in vain are deteriorating and constantly building. The cells die and come back to breed in an endless cycle. So much so, it is estimated that in about a year we changed to 100 of our cells. With the exception of the oxygen we get from the air, all raw materials that form every cell of our body, are obtained through food, so we can ensure that a portion of each piece of food we eat will end up being part of our own tissues , which fulfills the sentence: we are what we eat. What substances are needed in food Proteins, fats, carbohydrates and other nutrients The human body uses food basically two main functions, energy production and the formation of tissues and structures, ie for a function and another plastic energy. The energy comes from energy substrates where the key is glucose, which is obtained from the digestion of carbohydrates. Protein and fat can play a secondary role with energy producers, but that’s only if the body is forced to resort to, in the absence of carbohydrates, because it’s slow and metabolically expensive to produce energy from these two macro nutrients of carbohydrates. Therefore, carbohydrates play the role of providing the necessary glucose. Meanwhile proteins constitute the material that removes the amino acids are the building blocks with which the body forms most of its structures from the skin, nails, muscles, bones to the blood, enzymes and hormones. Therefore, their presence in the diet is also essential. Fat can serve both as energy substrate and plastic, and that can be used to produce energy as well as a constituent of various structures such as the brain, nerves, bone marrow and cell walls. It is therefore the third element of the diet. All three provide calories, four grams in the first two, while fat provides nine, meaning that the body uses to supply the production of body heat and energy as fuel. These macro nutrients needed in large quantities, tens and hundreds of grams, but others are also very necessary, to the point of being ESCENCIALES despite its necessity in the diet is negligible (minimal or low) of only milligrams or micrograms that are known as micronutrients. These vitamins and minerals your body needs to obtain and use energy from the first, plus multiple reactions involved in the cellular level.