Food sources of protein

During digestion, large molecules of proteins are broken down into simpler units called amino acids.

Amino acids are necessary for the synthesis of complete body proteins and many others tissue constituent.

Proteins are described as essential and nonessential proteins or amino acids. The human body requires approximately 22 amino acids in specific patterns for the synthesis of its proteins.

All the essential amino acids must be present simultaneously in the diet in order for the other amino acids to be utilized – otherwise, the body remains in negative nitrogen balance.

A lack of vital proteins in the body can cause problems ranging from indigestion to depression to stunted growth.

The body can make only 13 of the amino acids -- these are known as the nonessential amino acids.

They are called non-essential because the body can make them and does not need to get them from the diet.

The nine of these amino acids can be produced are called essential amino acids, and they must be supplied in the diet.

They are methionine, threonine, tryptophan, leucine, isoleucine, lysine, valine, phenylalanine and histidine.

If the protein in a food supplies enough of the essential amino acids, it is called a complete protein.

If the protein of a food does not supply all the essential amino acids, it is called an incomplete protein.

All meat and other animal products are sources of complete proteins. Spirulina contains all the essential amino acids. Soy comes close to being a complete plant protein.

These include beef, lamb, pork, poultry, fish, shellfish, eggs, milk, and milk products.

Protein in foods (such as grains, fruits, and vegetables) are either low, incomplete protein or lack one of the essential amino acids. These food sources are considered incomplete proteins.

To obtain a complete protein form incomplete protein foods, one must combine them carefully so that those foods that are low or missing an essential amino acid will be balanced by another food that supplies that amino acid.
Food sources of protein