Learn the differences between essential and non-essential amino acids.
The difference between essential and non-essential amino acids depends on whether they can be made from the body itself.
There are 20 different amino acids that make up all the proteins in humans. These are needed to replenish tissue, red blood cells and enzymes. Of these, 12 can be made by the body. They are known as non-essential amino acids because they do not need to be obtained from one's diet.
The other eight (some authorities say nine), the essential amino acids, cannot be made by the body and must be obtained from one's diet. Proteins in meat have all the essential amino acids; vegetables, with the exception of soybeans, are incomplete proteins in that they don't have all the essential amino acids.
By combining certain foods collectively, all essential amino acids can be ingested. For example, whole grain cereal combined with legumes and eaten together as complimentary foods form a complete source of essential amino acids.