Essential amino acids

Amino acids are formed of an amino group, a carboxyl group, and a side chain. Human body is unable to synthesize 9 essential amino acids. These essential amino acids must be obtained from food. The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Such amino acids as arginine, cysteine, and tyrosine may be required in particular situations for premature babies and in people suffering from liver disease. Meat, fish, eggs, and dairy products are important sources of high quality proteins. Essential amino acids in these products can satisfy human requirements. The food proteins such as egg albumin, milk casein, and wheat gluten are digested into their constituent amino acids and then absorbed from intestine. Amino acids in the body are connected by peptide chemical bonds forming proteins such as enzymes, hormones as well as structural, transport, and contractile constituents of the body. Plant foods taken separately are less suitable protein sources. However, balanced vegetarian diets can also satisfy human protein needs if they harmonize each other with essential amino acids.