<Tr> <Td> Suggested function from deprivation effects or active metabolic handling, but no clearly - identified biochemical function in humans </Td> </Tr> <Tr> <Td> Limited circumstantial evidence for trace benefits or biological action in mammals </Td> </Tr> <Tr> <Td> No evidence for biological action in mammals, but essential in some lower organisms . (In the case of lanthanum, the definition of an essential nutrient as being indispensable and irreplaceable is not completely applicable due to the extreme similarity of the lanthanides . Thus Ce, Pr, and Nd may be substituted for La without ill effects for organisms using La, and the smaller Sm, Eu, and Gd may also be similarly substituted but cause slower growth .) </Td> </Tr> <Table> <Tr> <Td> </Td> </Tr> </Table>

Most abundant element in earth's crust and mantle