Although most commonly known for its toxic properties, arsenic (As) has been shown to have beneficial actions when fed in very small amounts to laboratory animals. Numerous studies with rats, hamsters, minipigs, goats, and chicks have provided circumstantial evidence suggesting that arsenic is essential, but its physiological role has not been clearly defined. However, there is evidence that arsenic intake affects taurine and polyamine concentrations in plasma and tissues.
Deficiencies: The most impressive reported sign of arsenic deficiency is decreased growth of goats, impaired success of the first service and conception rates, greater absorption of fetuses during pregnancy, and higher mortality rate during the second lactation. There is often sudden death, and the mitochondria of the cardiac muscle showed ultrastructural changes in deficient goats. The most consistent signs of arsenic deprivation in rodents are decreased growth, higher death rate of young, rougher and yellowish hair coats (in white rats), elevated erythrocytes osmotic fragility, elevated spleen iron and splenomegaly. However, the severity and variation of these deficiency signs depend upon several dietary factors including the zinc, arginine, choline, methionine and guanidoacetic acid content. These substances are interrelated because they are effectors of methionine metabolism. Arsenic-deprived chicks drank and excreted more water, exhibited slower growth, usually had leg abnormalities, and arginine-supplemented deficient chicks had elevated hepatic zinc levels but depressed content of arsenic, iron and manganese in this tissue. Arsenic may be important under certain circumstances in humans. For example, arsenic, independent of omega-3 fatty acids, increases bleeding time. This implies that it may be a plausible candidate for the unknown factor in fish responsible for increased bleeding time. In addition, a recent human study suggested that arsenic homeostasis is altered by hemodialysis, and that low serum arsenic is correlated with central nervous system disorders, vascular disease, and "possibly" cancer.