Sources of protein, human protein requirements, and obtaining protein within specific diet patterns.

Protein is a macronutrient consisting of amino acid structures. Amino acids are molecules made up of nitrogen, oxygen, carbon and hydrogen, and are used for building most body tissues. Amino acids are needed for all kinds of growth and repair and the production of enzymes and hormones. Some amino acids are termed "essential" as they cannot be synthesised in the body and must be obtained from dietary sources.

In some cultures, meat and fish are considered the main or best source of protein, and it is sometimes assumed that vegetarian and vegan diets will lack sufficient protein, especially if they also exclude eggs and dairy products. Fortunately, plant-based foods can provide all the essential amino acids and it is not necessary to eat meat or fish to obtain sufficient protein. Nonetheless, many people interested in transitioning diets are concerned about obtaining sufficient protein to maintain good health.