Selenium - how much do you need?

Selenium is a very important micro nutrient. I have been doing some reading about selenium and vitamin E and vitamin C and stumbled across this very important information. It was my understanding that the RDI for selenium was set to give a selenium level of 1.0 micro mol per liter in blood. This level was supposed to give maximum levels of glutathione peroxidase. However as the graph below shows, blood levels of more than 1.0 μmol per litre can often result in higher levels of glutathione peroxidase (GPx).


So when I found out that selenoprotein-P was a better indicator of selenium levels in the body, thus making it a better indicator of selenium status I was not surpised. The key results from this study was that:

• NZers have low levels of selenium. Even though our bread is mostly made from Australian wheat which has increased our selenium levels, our intake is still low being an average of 28μg a day (the US RDI is 55μg).
  
• That selenium iun Selenomethionine is almost twice as bioavailable than selenite. This shouldn't surpirse us as selenomthionine is selenium bound to a protein (methionine) and this is the form that is found in plants and animals. Where as selenite is a rock.
  
• Glutathione peroxidase is maximized in blood with 50 μg of selenomethionine but took 80μg of selenite
• That intake at 70 μg selenomethionine (10μg in diet at 60μg in suppliment) did not maximize the selenoprotein-P levels in blood.
  
• You can measure your selenium status with a blood test. If your total selenium in your blood is appromiatly 80 μg/l then your body has enough selenium.
  

So if taking this data an applying it to NZ situation. We on average eat 28μg of selenium a day, so we need to suppliment with 40 μg a day. (I would be slightly more than this to maxamize the blood levels, however can't conclude from this study what that level would be). Make sure you suppliment with a chelated (protein bound) form of selenium eg selenomthionine.

Picture credit: Unfortuately I can't find the paper that this was orginally taken from! When I find it in my filing system I will upload the credit.
Paper credit: Xia,Y., Effectiveness of selenium supplements in a low-selenium area of ChinaAmerican Journal of Clinical Nutrition, Vol. 81, No. 4, 829-834, April 2005
© 2005 American Society for Clinical Nutrition