What is protein?

Calories are made up of three macronutrients: carbs, proteins, and fats which yield energy for the body.

  • Carbs yield 4 calories per gram and is mostly used to help your bodily functions and movements.
  • Fats yield 9 calories per gram meaning you get more energy per gram. That’s why it’s important to eat a moderate amount of fats in your foods.
  • Proteins yield 4 calories per gram and is mainly used in rebuilding your bodies daily breakdown from stress applied on it.
Jim White
Nutrition & Dietetics
Proteins are an essential part of every cell in the body. They serve several purposes: they are the major components of muscles, skin, tendons, blood vessels, and hair. They can also help to speed up reactions in the body (enzymes), provide structure for our bodies which help in our everyday movements from walking to digestion. These body proteins are constantly being broken down and replaced especially when put under stress such as exercise. The replacement of these broken down proteins comes from the protein in the foods we ingest, which is why incorporating protein into your daily diet is very important for healthy body function.
Alberta Scruggs
Nutrition & Dietetics
Protein is a macronutrient and one of the six nutrients needed for a healthy diet. Protein is an organic molecule (containing carbon, hydrogen, oxygen, nitrogen and sometimes sulfur), and is composed of one or more chains of amino acids in specific order.

Protein can be found in plant or animal tissue and is considered a food source (Providing 4 kcalories per 1 gram in the diet). It supplies essential amino acids to the body and is vital for the structure, function and regulation of the body's cells, tissues and organs. Examples of protein molecules include enzymes, hormones and antibodies.
Laura Motosko, MSEd, RD
Nutrition & Dietetics

All food is composed of three macronutrients: protein, fat and carbohydrate. Protein is used to build and repair tissue, form enzymes and hormones, and antibodies to fight infection. Good sources of protein include tofu, nuts, seeds, lentils, beans, beef, chicken, turkey, fish, pork, eggs, milk, cheese and yogurt.

Ms. Ashley Koff, RD
Nutrition & Dietetics
Proteins are organic compounds comprised of amino acids; as such, one often refers to an amino acid as the 'building block' of proteins. Considered a macronutrient, proteins, along with carbohydrates and fats, are a core part of our daily intake. Ideally, we look to consume the entire array of amino acids (21), but there are some (8) that the body doesn't make -- these are called essential and thus we need to consume them from our dietary choices (note: there are a few that certain populations -- due to their genetic makeup or injury -- may require from the diet so they are often termed 'conditionally essential'). Proteins are found in both animal and vegetable sources; however, each food source contains differing numbers and amounts of amino acids. The terms "complete" or "high quality" protein are used to refer to those that provide all of the essential amino acids in a proportion needed by the human body.
Michael T. Murray, ND
Naturopathic Medicine
The word "protein" is derived from the Greek proteios, or "primary." The name is fitting, because after water, protein is most plentiful component of our body. The body manufactures proteins for the production of hair, muscles, nails, tendons, ligaments, and other body structures. Proteins also function as enzymes, hormones, and important components of other cells, such as our genes. The human body contains between 30,000 and 50,000 unique proteins. The building blocks of all proteins are molecules known as amino acids.
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Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Proteins are complex molecules. They comprise a combination of different amino acids, which are important building blocks that your body uses to build important structures, like healthy cells, enzymes, antibodies and muscle. Protein is also an important source of energy for the body. One gram of protein provides four calories of energy.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.