OTHER TRACE ELEMENTS

Numerous mineral elements have been suggested to be essential nutrients for humans based on a few gross observations in one or two species of animals by one or two research groups. However, many of the changes described as evidence for essentiality were not very marked, were not necessarily indicative of a suboptimal biological function, or were obtained under less than satisfactory experimental conditions. Specific biochemical functions have not been defined for any of these elements. Most likely none of these mineral elements, which include the following, are of nutritional concern if intakes are near those in a typical, well-balanced diet.

Aluminum: Even without considering pharmaceutical sources, the typical daily dietary intake of aluminum varies widely, from 3 to 100 mg. Significant sources of aluminum include baked goods prepared with chemical leavening agents (i.e., baking powder), processed cheese, grains, vegetables, herbs and tea. Aluminum toxicity apparently is not a concern for healthy individuals. Cooking foods in aluminum cookware does not lead to detrimental intakes of aluminum. Ingestion of high dietary aluminum most likely does not cause Alzheimer’s disease, but may exacerbate this disease. Moreover, high intakes of aluminum through such sources as buffered analgesics and antacids by susceptible individuals (i.e., those with impaired kidney function including the elderly and low-birth-weight infants) may lead to pathological changes.

Bromine: The typical daily dietary intake of bromine is 2 to 8 mg. Foods high in bromine are grains, nuts and fish. Bromine is normally ingested as the bromide ion which has a low degree of toxicity; thus bromine is not of toxicological concern in nutrition. Limited findings suggest that bromide may be nutritionally beneficial; (e.g., insomnia exhibited by some hemodialysis patients has been associated with bromide deficiency).

Cadmium: The typical daily dietary intake of cadmium is 10 to 20 µg. Significant sources of cadmium include shellfish, grains (especially those grown on high cadmium soils) and leafy vegetables. Cadmium has a long half-life in the body and thus high intakes can lead to accumulation resulting in damage in some organs, especially the kidney. The Reference Dose (RfD) (safe daily intake over a lifetime) for cadmium is 0.5 µg per kg body weight.

Germanium: The typical daily dietary intake of germanium is 0.4 to 1.5 mg. Foods high in germanium include wheat bran, vegetables, and leguminous seeds. Germanium as an organic complex has been touted, but not proved, as having anticancer properties in humans. Some organic forms of germanium are less toxic than inorganic forms. Inorganic germanium toxicity results in kidney damage. Some individuals consuming high amounts of organic germanium supplements contaminated with inorganic germanium stores have died from kidney failure.

Lead: The typical daily dietary intake of lead is 15 to 100 µg. Significant sources of lead include seafood and plant foodstuffs grown under high lead conditions. In rats and pigs, lead deficiency reportedly has adverse effects including depressed growth and disturbed iron metabolism. Although lead may have beneficial effects in small amounts, lead toxicity is of more concern than lead deficiency. Lead toxicity results in anemia, kidney damage and central nervous abnormalities. Ingestion of high amounts of lead from the environment by children, particularly when anemic, has been associated with reduced intelligence and impaired motor function.

Lithium: The typical daily dietary intake of lithium is 200 to 600 µg. Rich sources of lithium include eggs, milk, processed meat, fish, milk, milk products, potatoes and vegetables. Lithium deficiency has been reported to result in depressed fertility and birth weight in rats and goats. Lithium is best known for its pharmacological properties; it is used as an anti-manic agent. Mild lithium toxicity, which has been observed with anti-manic use, results in gastrointestinal disturbances, muscular weakness, tremor, drowsiness and a dazed feeling. Severe toxicity results in coma, muscle tremor, convulsions and even death.

Rubidium: The typical daily dietary intake of rubidium is 1 to 5 mg. Foods high in rubidium include coffee, black tea, fruits, vegetables (especially asparagus), poultry and fish. Rubidium is a relatively nontoxic element and has not show to be of toxicological concern from the nutritional point of view. Rubidium deficiency apparently depresses growth and life expectancy in goats.

Tin: The typical daily dietary intake of tin is 1 to 40 mg. A significant source of tin is canned foods. Inorganic tin is relatively nontoxic. Tin deficiency has been reported to depress growth in rats.

For further information:

Nielsen, F. H. (1996) Other Trace Elements. In: Present Knowledge in Nutrition (Ziegler, E. E. and Filer, L. J. Jr., eds.), 7th ed., pp. 353-377. International Life Sciences Institute Press, Washington, DC.

Prepared By:

Forrest H. Nielsen, PH.D.
Director
USDA, ARS Grand Forks
Human Nutrition Research Center
P.O. Box 9034, University Station
Grand Forks, ND 58202-9034
Phone: 701-795-8456
FAX: 701-795-8395
Email: fnielsen@gfhnrc.ars.usda.gov

Michael Dunn, Ph.D.
Associate Professor
Department of Food Science and Human Nutrition
University of Hawaii
Honolulu, HI 96822
Phone: 808-956-3837
FAX: 808-956-4024
Email: mdunn@hawaii.edu