ABSTRACT
The essentiality of arsenic has been demonstrated for several animal species, including rats, chicks, and goats. Rat studies indicate that boron may be beneficial for optimal calcium metabolism, and therefore, for optimal bone formation. Fluorine has not been demonstrated to be an essential nutrient for the human or animals. The essentiality of nickel has been reported for the chick, rat and other animals, but its importance in human health has not been well established. Silicon appears to be an essential element for the chick and rat, but a corresponding need for the human has not been established. The majority of the sulfur present in the body exists as the sulfur-containing amino acids; methionine, cystine, cysteine, and homocystine. Vanadium is considered essential for chicks and rats. Specific biological functions of vanadium are unclear, but it may be involved in lipid metabolism and in bone development.
