Protein: you hear a lot about it and you know it’s important. Learn why it’s essential to good health and good eating.

What protein is and what it does

Proteins, along with fats and carbohydrates, are the macronutrients that form the basis of our diets. In our bodies proteins perform a range of duties, from building new cells to regulating metabolism to helping cells communicate. Proteins form antibodies to shuttle oxygen throughout the body in the form of hemoglobin, as well as build muscle.

Protein provides us with energy (calories). Like carbohydrates, protein contributes 4 calories per gram, versus 9 calories per gram in fats.

For many people, upping the amount of protein in the diet may help promote weight loss and improve body composition — learn more about Protein & Weight Loss.

Amino acids

Amino acids, of which there are about twenty, are the LEGOs of proteins. Our DNA directs the body to join various combinations of amino acids in a variety of sequences and three-dimensional shapes for an arsenal of about 10,000 different body proteins, each serving a unique function. Our bodies can make about 11 of these amino acids, leaving 9 that we must get from food. These remaining 9 are called essential amino acids, since it is essential that we get them from our diet.

Protein everyday

While our bodies can store fats and carbohydrates to draw on when needed, they cannot store amino acids. We need a fresh source each day in order to build the body proteins we need. If the body is missing a particular amino acid to form the protein it needs, it will pull that amino acid by breaking down existing muscle protein. If we consistently lack protein we lose muscle weight, energy and, eventually, fundamental functions. For an estimate of how much protein you should be getting each day see our Protein Calculator.

Think you’re not getting enough protein? Find 10 Ways to Eat More Protein.

Protein sources

Many foods contain protein in some form. Here are the main sources of dietary protein:

• Meat, poultry, eggs, dairy, and fish are complete sources of protein because they contain all 9 essential amino acids. Some animal protein sources—most notably red meat and whole dairy products—can also be high in saturated fat, which can raise cholesterol levels. Learn more about lean sources of animal-based protein.
• Soy, often in the form of tofu, or soy milk, is a popular plant-based source of protein since it, like animal-based protein, contains all 9 essential amino.
• Nuts, seeds, beans, peas, and whole grains can be terrific sources of protein. One thing to keep in mind with plant sources of protein, is that not all plant proteins are equal. With the exception of soy and quinoa, plant foods don’t contain all 9 essential amino acids. But certain plant foods complement each other with their amino acid profiles. For example, beans tend to be low in one amino acid that grains have plenty of, so combining these foods forms a complete protein. Learn more about complete plant proteins and vegetarians and protein.

Find out just how much protein different foods contain with our Guide to Protein Sources.