Doctor’s Analysis: The Dangers of Selenium Supplementation

Up until recently, selenium was widely touted for its ability to reduce the risk of diabetes and prevent certain forms of cancer. This idea developed on the basis of studies conducted in the early 1970’s which showed that selenium might reduce the effects of oxidative damage to cells thus prolonging cell life and reducing the risk of chronic disease. Recently, the potential dangers of selenium in high doses have become apparent.

What exactly is selenium? Selenium is a trace mineral which is needed only in small quantities by the body. It’s incorporated into the structure of certain proteins producing complexes which have antioxidant properties. On the basis of this, it was thought that selenium might play an active role in preventing the type of cell damage which leads to chronic disease.

It appears that selenium does function as an antioxidant at low levels but when levels are increased, it appears to have the opposite effect. At these higher levels it becomes a pro-oxidant and may actually accelerate cell damage by oxidation.


A trial carried out in 2007 first pointed out the potential dangers of selenium supplementation. This study looked at the effects of selenium supplementation on the incidence of type 2 diabetes. Subjects were given 200 micrograms of selenium per day and followed over a seven year period.

Surprisingly, at the end of the seven year period, the subjects taking selenium supplements were fifty percent more likely to have developed type 2 diabetes. This was sobering news to people who had taken the supplement to help prevent the health consequences of diabetes.

Deficiency of selenium is quite uncommon. The recommended intake per day is around fifty-five micrograms per day for adult which is usually readily obtained from the diet.

Foods high in selenium include cereals, meats, nuts, and seafood. Due to these studies which highlight the dangers of selenium at higher dosages, it’s recommended that you not exceed two hundred micrograms per day.

If you take a daily multivitamin, it’s recommended that you check the bottle to see how much selenium it contains. Some multivitamins contain up to seventy micrograms of selenium in supplemental form. When combined with dietary sources, you could go easily go beyond the two hundred microgram upper limit.

If your multivitamin contains more than twenty micrograms of selenium, it may be best to switch to a multi-vitamin without this supplement added due to the possible dangers of selenium supplementation.



Due to the results of this large, randomized study and the fact that selenium appears to act as a pro-oxidant at high doses, selenium supplementation isn’t recommended. Most people will get sufficient amounts of this trace mineral through diet.

Also be aware of how much selenium is contained in your daily multivitamin if you take one. Avoid getting more than two hundred micrograms per day to avoid the potential dangers of selenium and its ability to increase cell damage at high levels.