Macronutrients are the components of food from which we get energy: protein, carbohydrate, and fat. They are called that because we consume them in relatively large quantities, grams, tens of grams, and sometimes hundreds of grams a day. Alcohol also provides calories, but it is not (hopefully) a nutrient from which you are deriving a large percentage of your calories each day. We will talk about alcohol at some point in the future.
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The macronutrients provide us with energy. In nutrition, the unit of energy is the calorie. The calorie is defined as the amount of energy it takes to raise 1 gram of water 1ºC. But this is where it gets interesting: in nutrition, we do not usually talk about the calorie; we talk about the Calorie.
One Calorie is equal to the energy it takes to raise 1 kilogram (1000 grams or 2.2 pounds) of water 1ºC. So, one Calorie is equal to 1000 calories. Often it is abbreviated to Cal or kcal. Sometimes notation can be confusing.
Fortunately, whenever someone is talking about Calories in food, they are referring to the big ‘C’ Calorie. The details are not very important, but the concept is: it takes a lot of energy to run your body.
The Calories that you get from food are responsible for maintaining your body temperature, performing the metabolic reactions that keep you alive, and for your activity, to name a few things.
Besides providing the energy that you need to stay alive and do the things that you want to do on a daily basis, each macronutrient has other functions: they can affect hormones, transport vitamins, be structural components of cells and organs, protect and insulate the body, etc. We’ll talk about each macronutrient and its functions in upcoming posts.