| Element
|
Description
|
Excess
|
| Bromine
|
Possibly important to basement membrane architecture and tissue development, as a needed catalyst to make collagen IV.
|
bromism
|
| Arsenic
|
Essential in rat, hamster, goat and chicken models, but no research has been done in humans.
|
arsenic poisoning
|
| Nickel
|
Nickel is an essential component of several enzymes, including urease and hydrogenase. Although not required by humans, some are thought to be required by gut bacteria, such as urease required by some varieties of Bifidobacterium. In humans, nickel may be a cofactor or structural component of certain metalloenzymes involved in hydrolysis, redox reactions and gene expression. Nickel deficiency depressed growth in goats, pigs, and sheep, and diminished circulating thyroid hormone concentration in rats.
|
Nickel toxicity
|
| Fluorine
|
Might have a role in biologic mineralisation, and fluoride deficiency symptoms have been found in goats, but there is no clear evidence of essentiality in humans. Research indicates that the primary dental benefit from fluoride occurs at the surface from topical exposure. However, even if not essential, fluorine would still be a beneficial element for this reason. Of the minerals in this table, fluoride is the only one for which the U.S. Institute of Medicine has established an Adequate Intake.
|
Fluoride poisoning
|
| Boron
|
Boron is an essential plant nutrient, required primarily for maintaining the integrity of cell walls. Boron has been shown to be essential to complete the life cycle in representatives of all kingdoms of life. In animals, supplemental boron has been shown to reduce calcium excretion and activate vitamin D.
|
No acute effects (LD50 of boric acid is 2.5 grams per kilogram body weight)
|
| Lithium
|
Based on plasma lithium concentrations, biological activity and epidemiological observations, there is evidence, not conclusive, that lithium is an essential nutrient.
|
Lithium toxicity
|
| Chromium
|
Proposed to be involved in glucose and lipid metabolism, although its mechanisms of action in the body and the amounts needed for optimal health are not well-defined
|
chromium deficiency / chromium toxicity
|
| Silicon
|
Deficiency symptoms have been found in chickens and rats, though not humans. Circumstantial evidence suggests that it is an essential nutrient, probably having an effect on the function and composition of brain and bone.
|
|
| Vanadium
|
Has an established, albeit specialized, biochemical role in other organisms (algae, lichens, fungi, bacteria), and there is significant circumstantial evidence for its essentiality in humans. It is rather toxic for a trace element and the requirement, if essential, is probably small.
|
|
| Tin
|
Rats fed a tin-free diet exhibited improper growth, but the evidence for essentiality is otherwise limited.
|
Tin poisoning
|
| Other
|
Tungsten, the early lanthanides, and cadmium have specialized biochemical uses in certain lower organisms, but these elements appear not to be used by mammals.
|
|