Selenium is an essential mineral that a healthy body needs to function normally. This mineral is incorporated into several different proteins, called selenoproteins, which require selenium to function properly. Much scientific research has gone into how proteins use selenium and how these proteins function to prevent cancer.
Antioxidants and Reactive Oxygen Species
When oxygen is processed during metabolism, a normal byproduct is reactive oxygen species, which can cause cellular damage and might ultimately contribute to cancer. Antioxidants process reactive oxygen species into molecules that are harmless to the body, like water, thus limiting the exposure of the body to cancer-causing reactive oxygen species. Oregon State University reports that some selenoproteins, such as Sep15, function as antioxidants and have been shown to help prevent cancer.
Cancer Research
Several clinical studies have been conducted investigating the health effects of selenium supplementation. These studies were conducted based on the finding that people with low levels of selenium in their blood were at an increased risk of cancer death, according to the University of Maryland Medical Center. For men who had low levels of selenium in their blood, taking this mineral as a supplement lowered their risk of prostate cancer by more than 60 percent. Of course, selenium is not a cure-all for every case of cancer. Although it has been shown to be significantly effective in a large population of patients, it is not certain that it will be effective in every individual case.
Dietary Sources
The best dietary sources of selenium, according to Oregon State University, are meat from animal organs, such as liver, and shellfish. Grains and vegetables do not need selenium to grow but often incorporate it if it is present in the soil. However, because plants do not need it to survive, the levels of selenium present in grains and vegetables can vary widely. For plants grown in the United States, grain tends to be a better source of selenium than vegetables. Brazil nuts, depending on the soil in which they are grown, also can be a great source of selenium, notes the Office of Dietary Supplements of the National Institutes of Health.
Daily Requirements and Toxicity
Adults over 19 require about 55 micrograms of selenium per day, according to the Office of Dietary Supplements, which is enough for its anti-cancer effects. A healthy diet for women who are pregnant includes 60 micrograms per day, and women who are breastfeeding should get about 70 micrograms per day. It is important to note that, like other essential minerals, too much selenium can be toxic. Exceeding a dose of 400 micrograms per day might result in selenosis, an illness with symptoms such as stomach upset, loss of hair and white blotches on the nails.
