Polarized light micrograph of methionine crystals, one of nine essential amino acids in humans, with a key role in the absorption of selenium and zinc, in angiogenesis, and in tissue growth and repair. As a dietary supplement it may be beneficial in cases of Parkinson's, schizophrenia, depression, alcoholism, radiotherapy, asthma, and allergies. It is involved in many detoxifying processes, as the treatment of paracetamol poisoning, and it protects cells from pollutants, slows cell aging, and is a cytoprotectant against cisplatin, an anticancer agent. Chelating toxic heavy metals such as lead, copper, and mercury, it aids their excretion. Methionine is a precursor of two other amino acids, cystine and cysteine, and is also an intermediate of several phospholipids. It acts as a lipotropic, but the improper conversion of methionine can lead to atherosclerosis. Field of view size: 1.49 x 2.23 mm (0.059 x 0.088 in)