Selenium is an essential mineral found in minute amounts in the body. It works closely with vitamin E in some of its metabolic actions and in the promotion of normal body growth and fertility. Selenium is a natural antioxidant and appears to preserve elasticity of tissue by delaying oxidation of polyunsaturated fatty acids.
It is necessary for the production of prostaglandin, substances that affect blood pressure. A prostaglandin deficiency also results in a deficiency of other compounds necessary for keeping the arteries free from platelet aggregation.
Selenium improves certain energy-producing cells, including those of the heart, by ensuring adequate oxygen supply.
The selenium content of food is dependent upon the extent of its presence in the soil, whether directly, as in plant foods, or indirectly, as in animal products whose selenium levels are derived from feed. Even if selenium levels are adequate in the soil, the sulfur contained in widely used fertilizers and sulfuric compounds found in acid rain inhibit plant absorption of the mineral.
Selenium compounds in foods are easily reduced by heat, processing, and cooking. Refining of grains reduces selenium content by 50 to 75 percent, boiling by 45 percent.
Good food sources of selenium are brewer's yeast, f organ and muscle meats, fish and shellfish, grains, cereals, and dairy products.
The liver and kidneys contain four to five times as 1 much selenium as do the muscles and other tissues. | Selenium is normally excreted in the urine; its presence I in the feces is an indication of Improper absorption. Because it binds with toxic metals, the selenium that is ingested may not be assimilated.
The National Research Council recommends 50 to 200 micrograms of selenium daily. Doctors studing selenium suggest 250 to 350 micrograms may be needed. The average "good" diet may contain only 35 to 60 micrograms per day. Doses should not exceed 700 to 1110 micrograms daily for long periods of time unless under the supervision of a physician.
Male sperm cells contain high amounts of selenium. Substantial amounts are lost during sexual intercourse. For this reason, selenium requirements may be higher \ for men than for women.
The different selenium compounds have varying degrees of toxicity. For example, dimethyl selenium is nontoxic; sodium selenite is more toxic than organic selenium; and selenium yeast is one-third as toxic as I sodium selenite.
High levels of selenium in soil have caused toxicity | and some deaths in animals who grazed on the grains. Selenium also contaminates water supplies located near irrigated irrigated land. Selenium intoxication has been reported as a result of industrial inhalation.
Toxic symptoms are loss of hair, teeth, and nails; dermatitis; lethargy; and paralysis. Severe overdose produces fever, an increased respiratory and capillary rate, gastrointestinal distress, myelitis, and sometimes death.
Selenium overdoses can interfere with fluoride assimilation, which helps to prevent tooth decay.
Deficiency Effects and Symptoms
A deficiency of selenium may lead to premature aging. This is because selenium preserves tissue elasticity.
A defective selenium absorption mechanism can result in neuronal ceroid lipofuscinosis, a disease that accumulates pigment in nerve cells and is characterized by mental retardation, diminished vision, nerve disorders, and eventually death.
Selenium is essential for reproduction. Animal tests reveal that selenium-deficient rats produced immobile sperm and most of the sperm were broken near the tail. Other studies show that a selenium deficiency results in infertility.
Studies in Australia show that a selenium deficiency may relate to crib death.
Beneficial Effect on Ailments
Selenium when combined with protein is beneficial in treating kwashiorkor, a protein-deficiency disease.
Silicon is present in the connective tissues of the body such as tendons, cartilage, and blood vessels, and it is possible that the mineral is essential for their integrity. Silicon may work with calcium to make strong bones, therefore being an not given the trace element.
Dr. Julian E. Spallholz of the Veterans Administration Hospital in Long Beach, California, has demonstrated through experiments with mice that selenium may increase resistance to disease by increasing the number of antibodies thet neutralize toxins. Selenium supplements enabled mice to produce significantly more than those that were not given the trace element.
.Archives of Environmental Health, September/October 1976, reports that in a study of the relationship between cancer incidence and soil distribution of selenium in the United States, areas with high selenium levels showed significantly lower overall male cancer death rates. Also in these areas, in both men and women, fewer cancers were noted in those organ systems involved with the assimilation, metabolism, and excretion of selenium.