Selenium
Benefit
Selenium is able to play such a protective role in the body because it increases antioxidant capabilities and the quality of blood flow, therefore enhancing the body’s resistance against diseases and stress. Selenium is often praised for its role in antioxidant activity, which lowers free radical damage and inflammation. This is thought to be due to different types of selenoprotein found in selenium.
This means that selenium benefits your body by potentially helping prevent common forms of cancer, fight off viruses, defend against heart disease, and slow down symptoms correlated with other serious conditions like asthma.
Harm
Keshan disease is a cardiomyopathy, which is characterized by abnormalities in the ECG, cardiomegaly and eventually cardiac failure. The essential pathological feature of the disease is the presence of multiple necrotic areas in the myocardium. It is usually seen in children and in women of reproductive age. It seems to be linked to stress, such as viral infections, in people who are selenium deficient. This syndrome has been successfully controlled with the government-introduced supplementation of selenium in the affected areas.
Another disease which has traditionally been linked to selenium deficiency is Kashin-Beck disease, which is a disfiguring form of arthritis resulting from cartilage atrophy, breakdown and death, usually occurring in children between 5 and 13 years of age, seen in some parts of China, Tibet and Siberia. The incidence of this condition has also been brought down by supplementation of selenium.
Again, it is suspected that selenium deficiency predisposes to a higher risk of cretinism by aggravating the effects of iodine deficiency. Male infertility has also been thought to have some links to low levels of selenium in the body.