Although numerous studies with rats, hamsters, minipigs, goats and chicks have indicated that
arsenic is an essential nutrient, the physiological role of
arsenic is open to conjecture. Recent studies have suggested that
arsenic has a physiological role that affects the formation of various metabolites of
methionine metabolism including
taurine and the
polyamines. The concentration of plasma
taurine is decreased in
arsenic-deprived rats and hamsters. The hepatic concentration of
polyamines and the specific activity of an
enzyme necessary for the synthesis of
spermidine and
spermine,
S-adenosylmethionine decarboxylase, are also decreased in
arsenic-deprived rats. Thus, evidence has been obtained which indicates that
arsenic is of physiological importance, especially when
methionine metabolism is stressed (e.g. pregnancy, lactation,
methionine deficiency, vitamin B6 deprivation). Any possible nutritional requirement by humans can be estimated only by using data from animal studies. The
arsenic requirement for growing chicks and rats has been suggested to be near 25 ng g(-1) diet. Thus, a possible human requirement is 12 μg day(-1). The reported
arsenic content of diets from various parts of the world indicates that the average intake of
arsenic is in the range of 12-40 μg. Fish, grain and cereal products contribute most
arsenic to the diet.