The human body uses amino acids to build proteins, which it then uses to build and repair tissues. Protein is also an important building block of bones, cartilage, skin, muscles and blood, and is used to make hormones and enzymes too. There are some amino acids for which the body is able to synthesise (non-essential), however for those that it cannot (essential amino acids) then consumption of amino acid rich foods, such as spirulina, leafy greens or avocados, must be sought. Alternatively, a supplementation with rich amino acid formulas may be necessary to maintain sufficient protein production. A lack of amino acids in the diet may result in the poor growth of finger and toenails, or the skin and hair.