Molybdenum

Is cofactor for xanthine, sulfide,

and aldehyde oxidases.

D eficiency difficult to produce;

growth depression.

Not known.

Excessive exposure in parts o f the

Soviet Union associated with

goutlike syndrome.

Nickel

Interacts with iron absorption;

may be a structural component

or cofactor o f a m etalloenzyme.

Depressed growth, hem atopoiesis,

and reproduction; disturbed

metabolism o f iron, copper,

and zinc; uitrastructural

changes in liver.

Not known.

Not known.

Selenium **

Is glutathione peroxidase cofactor;

in type 1 dciodinase; interacts

with heavy metals.

Depending on species, muscle

degeneration, pancreatic

atrophy.

Endemic cardiomyopathy

conditioned by selenium

deficiency.

D eficiencies and excesses known

in parts o f China; deficiency

due to total parenteral nutrition.

Silicon

Involved in calcification and as

cross-linking agent contributing

to the architecture and resilience

o f connective tissue.

Growth depression; structural

abnormalities o f the skull and

long bones; decreased amounts

o f collagen and hexosam ine

in bone.

Not known.

Not known.

Vanadium

Perhaps involved in regulation

o f a phosphoryltransferase

enzyme.

Growth depression; impairment

o f reproduction and lipid

metabolism; none o f these are

reliably reproducible.

Not known.

Not known.

Zinc

Is cofactor for enzym es

o f energy metabolism,

transcription, and translation.

Failure to eat; severe growth

depression; sexual immaturity;

skin lesions.

Growth depression; sexual

immaturity; skin lesions;

change of taste acuity;

decreased immunocompétence.

D eficiencies known in Iran and

Egypt; with total parenteral

nutrition; due to genetic disease,

traumatic stress.

‘Modified and reproduced, with permission, from W. Mertz: The essential trace elements,

S c i e n c e ,

213, 1332 (1981); and F, H. Nielsen: Ultratrace elements in nutrition.

A n n u . R e v . N u t r .

.

4,21 (1984).

f Bromine, cadmium, lead, and tin are not listed here because the evidence ft* their being essential is weak.

¥Probably essential, but farther studies are needed to establish this.

% is uncertain whether fluorine should 1» considered an essential element or a pharmacological agent. A fluoride concentration in drinking water of 0.9-1.0 mg/L is prophylactic for dental caries: consumption of

water with fluoride concentration greater than 1.5 mg/L, during the years of tooth development, produces mottling.

"Discussed in Chapter 30.

'iron and iodine are not true “trace" elements because of their relatively high daily requirements and their high concentrations in the body.

“Discussed in Chapter 29.

“ Interactions with vitamin E may also be important.

fu n ction s for arsenic, boron, fluorine, lithium, nickel, silicon, and vanadium are still partially or completely hypothetical. They are based on the symptoms of the deficiency diseases produced.