Selenium supplements are supplements taken by those who have difficulties getting enough selenium in their diets or who have conditions that make it difficult for them to absorb selenium. Selenium is extremely important to human and animal health; small amounts of selenium are needed to ensure certain proteins and enzymes function properly. Selenium deficiency can cause problems in human growth and health, but deficiency is very rare, so the health effects are not particularly well documented. Some studies have suggested that selenium supplements could be used to reduce one's risk of cancer and that selenium deficiency could increase one's chance of getting HIV/AIDS, but there is not enough evidence to conclusively state that the results of these studies are factual.
The amount of selenium an individual needs to take in each day is generally measured in micrograms; one microgram is several orders of magnitude smaller than a milligram. The amount of selenium required in the human diet, then, is very small. Almost any healthy, balance diet contains enough selenium to render selenium supplements unnecessary. Typically, only those with specialized conditions, such as intestinal problems that severely limit the absorption of selenium, are advised to take selenium supplements.
Excess selenium can actually cause selenium toxicity, so those who do take selenium supplements must be careful to ensure they do not take too much. Generally speaking, one should not take in more than 400 micrograms of selenium each day; doing so can cause a condition known as selenosis. Selenosis can cause a wide range of problems, from bad breath and hair loss to liver damage, neurological damage and even death. Other possible symptoms include gastrointestinal disorders, loss of fingernails and toenails, irritability, and pulmonary edema. Few people need selenium supplements, and those who do must take great care to avoid consuming too much selenium.
Selenium supplements come in several forms. Some come in tablets, and some come in capsules. Extended-release tablets are also an option; these release the selenium into the body over the course of a few hours.
The recommended dosages for selenium vary based on an individual's age and gender, but are generally between 10 micrograms and 80 micrograms. Males generally need more selenium than females, but nursing or pregnant females need the most selenium in their diets. It is usually not difficult to meet or exceed these recommended daily values through a normal, healthy diet.