Some evidence suggests that selenium supplementation is also helpful in reducing menopausal symptoms. In addition, it has been suggested, with vitamin E, for male impotency. Although these uses need further study, it is certainly possible that selenium can increase sexual potency and fertility by improving sperm production and motility and by protecting against oxidative damage in the testes and related organs. (Fertility, potency, and sexuality are, however, more intricate than just these physiological processes.) I am sure that we will find more uses for selenium in the near future.
Deficiency and toxicity: Just 20 years ago, selenium was considered a nonessential toxic mineral. There is still justifiable concern over elemental selenium toxicity, but we are finding that the value of inorganic selenium salts, such as sodium selenite, and organically bound selenomethionine at appropriate levels far exceeds the potential to cause problems. Actually, selenium can be tolerated for short periods in higher amounts than was previously thought. Inorganic selenium, usually as sodium selenite, is the common form found in nature and can be more toxic in the short term than the organically bound selenium in the form of selenomethionine. While more than 1 mg. per day of sodium selenite is likely to produce symptoms, we may tolerate several milligrams daily of organic selenium without toxicity problems occurring. However, it is possible that the organic forms of selenium accumulate in the body and may be of long-term concern. Different authorities provide different figures for selenium intake and divergent viewpoints as to the question of toxicity; some sources state that toxicity is possible when 2,000 mcg. (2 mg.) are taken daily by people who already have total body stores of over 2.5 mg. (the normal level is 1 mg.), or when the water or food regularly contains over 5-10 ppm. Selenium is thought to interfere with sulfur compounds and even replace the sulfur in the body, as these two minerals are very similar biochemically, and thus may decrease a number of enzyme actions. The complexity of these issues in regard to selenium point out the importance of individual assessment and monitoring when taking certain supplemental products.
There is no clearly defined syndrome of selenium toxicity. Cattle that graze on selenium-rich soil have exhibited visual, muscular, and heart problems. Similar symptoms of toxicity have been found in humans living in high-selenium areas. Long-term ingestion of high amounts may cause problems with tooth enamel and strength, as higher selenium levels seem to increase tooth decay. One highly speculative theory is that selenium competes with fluoride in teeth, decreasing their strength. Other problems may include loss of hair, nails, and teeth, as well as skin inflammation, nausea, and fatigue. Some subtle symptoms that have been experienced include a garlic odor, metallic taste, or dizziness. Acute selenium poisoning can lead to fever, anorexia, gastrointestinal symptoms, liver and kidney impairment, and even death if the levels are high enough.
None of these symptoms should occur when selenium is taken in a therapeutic amount. There has been some fear of mutagenicity (that is, ability to cause developmental defects) of selenium in higher amounts. This might be true of the sodium selenite form, which may have both mutagenic and antimutagenic properties, depending on the amount. This theory needs further detailed study.