Selenium helps control these specific prostaglandins by controlling the free-radical damage that stipulates their production. Vitamin E is a partner with Selenium in protecting the body components against oxidative free radicals. Both Selenium and Vitamin E have their own specific modes of stopping free radicals, plus they have common modes. The two are synergistic, which means that the activity of both together is greater than the sums of the activity of each by itself. There are many other selenium supplements on the market.
Selenium can be toxic at very high doses.
This was first observed in animals that eat plants with toxic levels of Selenium. Toxicity in humans is rarely seen. However, toxicity has been reported in parts of the world where dietary Selenium levels are extremely high. In the Nutritional Prevention of Cancer trial, no evidence of Selenium toxicity has yet been observed with either 200 or 400 mcg per day, as indicated by routine examination of patient's nails and hair and liver function tests.