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A long chain of amino acids joined by peptide bonds, proteins are essential to all living organisms and regulate all aspects of the metabolism.
Twenty-two amino acids are linked together in various forms to create the many varied types of proteins, such as bone, hair or nails, and these processes are supervised by the nucleic acids RNA and DNA, the specific proteins that contain our genetic blueprint.
Eight of these amino acids, which can't be produced by the body, are classified as 'essential amino acids' - namely: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan; and a fully-balanced diet is needed to maintain optimal levels of these.
Symptoms of protein deficiency are many, but include anaemia, brittle nails, fatigue, hair loss and low sex drive.
Proteins, common in are diet, are found in greatest quantities in soya beans and other grain legumes, meat, eggs and cheese. See 'Amino Acid'; 'Peptide';