Selenium is a mineral that is required in very low doses for the body to function normally. It is an antioxidant, meaning that it prevents oxygen from damaging cells and reduces inflammation. These actions have led to speculation that it might also protect persons from chronic diseases that can develop from cell damage and inflammation, such as heart disease and cancer. Many people in North America get enough selenium in their diet. But many other people, particularly those in Europe, do not. Selenium is included in many multivitamins and is sold as a supplement itself, which many persons take to stay healthy. For example, some evidence links low blood selenium levels to heart disease, suggesting that receiving selenium supplements would prevent disease. However, it is not clear if such supplements are entirely safe. Other evidence suggests that high blood selenium levels are associated with higher cholesterol levels, implying that receiving selenium supplements could promote rather than prevent heart disease.