A food that contains all of the essential or non dispensable amino acids is know as a complete protein. If this food contains adequate amounts of the amino acids to maintain nitrogen balance and growth, the food is called a “high quality protein” Meats (chicken, beef, pork, lamb, veal, rabbit and seafood) are high quality proteins. If a food does not contain one or more essential (non dispensable) amino acids or the amount is insufficient for optimal protein synthesis is food is called “a low quality protein” Nuts, legumes (beans) and grains are low quality proteins.
Proteins provide 4kcal/gram. The amount of protein needed is dependent on age and growth (body size) and is based on the assumption that essential (non dispensable) amino acids are obtained in adequate amounts. The daily recommendation of protein is 10-35% of a 2000 kcal diet for an average person.
Proteins sources include meats, dairy products, eggs, nuts, seeds and soy products. Milk is a good source of protein but lacks some of the vitamins associated with other protein rich foods including iron, niacin, and vitamins E and B6. The Canada Food Guide recommends that a ¼ of the plate be proteins.