What is Protein?

Protein is an important part of life and nutrition; it is the substance that composes a large portion of your body’s structure.

Next to water, protein is the most abundant substance in the human body. It is part of all body cells and is a vital building block in the growth, maintenance and repair of the body tissue.

Proteins are made up of amino acids arranged in different combinations. Think of amino acids as the building blocks. There are 20 different amino acids that join together to make all types of protein. Some of these amino acids can’t be made by our bodies, so these are known as essential amino acids. It’s essential that our diet provide these.

A complete protein source is one that provides all of the essential amino acids. You may also hear these sources called high quality proteins. Animal-based foods; for example, meat, poultry, fish, milk, eggs, and cheese are considered complete protein sources.

An incomplete protein source is one that is low in one or more of the essential amino acids. Complementary proteins are two or more incomplete protein sources that together provide adequate amounts of all the essential amino acids. They are generally found in vegetable products like fruits, vegetables, pulses, grains and nuts.

However, by combining two or more of the “incomplete” proteins, a complete supply of essential amino acids is available. For example, baked beans on toast or rice and beans will form a complete protein and give the body all the essential amino acids.


  • Protein is needed for building, maintaining and repairing all body cells.
  • Protein is an important part of red and white blood cells. It aids in the clotting of blood.
  • Enzymes are important protein-containing substances in your body. They initiate essential chemical reactions.
  • Many hormones are made by proteins and help your body fight infections.


Animal Protein Sources: All meat and other animal products are sources of complete protein.

  • beef, lamb, pork
  • poultry, eggs, cheese, yogurt
  • fish, shellfish
  • milk and milk products

Vegetarian Protein Sources: Plant protein sources can be combined with other plant or animal products to form a complete protein; rice and beans, milk and wheat cereal, corn and beans. Protein in foods such as most grains, fruits, and vegetables are considered incomplete proteins, being either low in, or lacking, one of the essential amino acids, where as, these plant foods are considered complete proteins:

  • Nuts
  • Soy foods (tofu, tempeh, miso, and soy milk)
  • Sprouted seeds (each type of sprout differs in nutrient proportions, so eat a variety)
  • Grains (rice, breads, pastas; especially amaranth and quinoa, highest in protein)
  • Beans, legumes. and lentils
  • Hummus
  • Veggie Burgers
  • Baked Potato
  • Peanut Butter
  • Spirulina and chorella or blue-green algae (over 60% protein)


Check out these additional references:
Visit www.everydiet.org and www.webmd.com for additional information.