Selenium is an essential trace mineral that helps to build antioxidants in partnership with vitamins such as vitamin E. Together these help to protect to the cellular membranes in the body. Selenium itself, alongside a host of benefits, also increases antioxidant protective enzymes in the cells. Selenium is also vital to the activation and usefulness of the antioxidant Glutathione peroxidase. This antioxidant targets harmful hydgrogen peroxide in the body and helps to convert it to water. This process is important and helps to guard blood cells from damage as well as protecting the heart, liver, and lungs.

Selenium is contained in a variety of plants including garlic, asparagus, and grains, but the level will actually depend on the soil content in which these nutrients are grown. Some of the best means of obtaining Selenium in your diet are from Brazil nuts, meats fish and eggs. Other foods include kidney, tuna, crab and lobster.

Different geographic regions will however, often produce different levels of selenium in the foods based upon the soils quality. As such, some argue that foods grown in the depleted soils of large scale agricultural production farms have very little of this micronutrient. On the other hand though, excessive selenium can be dangerous. Taking over 1000 micrograms (1 milligram) daily can be toxic. Overdoses of selenium can result in selenosis an ailment which affects the hair, nails, and causes fatigue, irritability, and neurological damage.

Some studies have also linked high selenium intake with the possibility of developing type 2 Diabetes. Because high selenium levels are positively associated with the prevalence of diabetes, and due to the fact that deficiency is rather rare in the US, supplementation is not recommended in well-nourished and healthy people living in here.

Despite these findings, some studies have revealed that a selenium deficiency is linked to cancer. In rodent based studies, chemically induced carcinogensis has been prevented by dietary supplements of selenium. It is believed that selenium may have a protective effect by way of acting as an antioxidant or by enhancing immune function. While there are some studies which have not revealed the same correlation, many believe this remains a promising area of research.

Finally, selenium low soils, such as those found in sub-Saharan Africa have also begun to be investigated as a correlate to the epidemic rates of HIV in those areas. Whereas in the selenium rich soils of Senegal there seems to be lower levels of AIDS infection than on the rest of the continent. Low levels of selenium have been directly correlated with decreased immune cell count and disease progression, including risk of death, in patients suffering from AIDS.

Overall, the contradictory nature of the studies thus far suggests that more research is still needed to be done to confirm the exact effects of selenium. While having too little can be a problem and has been linked to the progression of deadly diseases such as AIDS and Cancer, other diseases such as Diabetes have been correlated with too high of levels of selenium. Best bet remains sticking to a diet naturally rich in selenium, and or supplementing at lower levels with other important vitamins and minerals. Tumor suppression was found in one study to result from a mix of Vitamin E (400 IU) and selenium (200 micrograms). These low levels of selenium, well below a harmful dose, should therefore be fine, and perhaps even beneficial.