Protein is essential to your body's proper functioning and survival, which is the short reason for why you need it.
What is protein?
Protein is actually a very broad term for the chains of amino acids found in the foods that we eat and throughout our bodies. There are between 20 and 22 protein-building amino acids – our bodies make more than half of them through the breakdown of proteins or from other amino acids, but nine amino acids are called "essential," meaning we must ingest them because the body cannot produce them on its own.
Our bodies need proteins that vary in their breakdown of essential amino acids, and we need protein every day because, unlike things like glucose, fat and certain vitamins, our bodies have no way to store amino acids. Thus, if we fail to eat enough complete protein every day, our bodies "go catabolic," meaning they break down existing tissues – starting with the muscles – to get the necessary amino acids.
There's a reason that our bodies need protein everyday and will go to great lengths to get it. In fact, there are between 30,000 and 50,000 different proteins in the body. Protein is essential to a majority of the body's functioning, including:
Immune response: Antibodies are proteins that attack a bacterium or virus that has entered the body. Antibodies work to neutralize the impact and prevent the foreign substance from causing infection or disease.
Supporting the tissues: Collagen is the most widespread protein in the body, as it is a part of the tendons, ligaments and bones. Myosin and actin – both proteins – help the muscles function.
Fluid balance: Proteins found in the blood help maintain the proper fluid levels in the body. They act as a buffer, remove excess hydrogen or add more when necessary to maintain the blood's pH levels. Blood proteins also protect against the accumulation of fluid in the tissues by pulling water into the capillaries.
Growth and development: Proteins are especially important for fetuses, infants and children whose bodies are growing rapidly.
Transporting oxygen around the body: The protein hemoglobin pairs with iron to move oxygen through the blood.
Breaking down food: Enzyme proteins break down other proteins into amino acids and work to remove waste.
What to know about eating protein
Protein requirements vary with age, sex, health and level of physical activity, but people rarely need protein supplements unless they're working to build a lot of muscle quickly.