I dont know if this has been posted before but here is one doctors opinion from acu-cell.com
"Selenium supplementation is an effective way to reduce excessive mercury levels. I have monitored
on a number of occasions a sharp drop in selenium levels when dental Amalgams
were removed, and
where subsequently Se lowly returned to previous levels again over a three to four week time period.
When people have no heavy or toxic metal concentrations in their body (that bind to selenium), most
of the time there are no negative symptoms when taking about 200mcg per day of selenium, however
when selenium is very low when first supplemented (perhaps due to toxic / heavy metal storage), and
larger amounts are taken, adverse effects are very commonly experienced the first few weeks due to
the heavy or toxic metals being eliminated by the body. In that case, I always urge my patients to slowly
increase their selenium dose from as low as 25mcg per day (or even lower), up to eventually the full
dose, which generally is around 100mcg or sometimes higher, depending on circumstances.
Organic forms of selenium (selenium yeast and selenomethionine, or selenocysteine) are always
preferable to inorganic forms such as sodium selenite because of their better absorption and lower
toxicity, even when ingested at much high amounts. In contrast, due to its free-radical promoting
oxidative nature, inorganic selenium is mutagenic and has caused cataracts at high doses in animal
studies, while organic selenium is less toxic, and does not have mutagenic or oxidizing activity.
Deficiency of selenium leads to lowered glutathione peroxidase activity (cardiovascular disease) and
it is implicated with a higher risk for cancer of the liver (particularly from hepatitis B), lungs, breast, skin,
colon, rectum and prostate.
It is still not clear whether the lowered risk of developing certain cancers from taking about 200mcg of
selenium per day also applies to individuals who previously exhibited normal levels of selenium, or only
to those with lower levels before supplementing that amount.
Although selenium and Vitamin E work together synergistically in that they carry out antioxidant and
immunostimulating functions, they compete with each other on a biochemical level, where increasing
the one requires an increase of the other, otherwise ratio problems occur. The same effect happens
to Vitamin E when higher amounts of Vitamin C are supplemented, despite both being antioxidants.
Although there are reports that Vitamin C inhibits selenium absorption by inactivating it in the stomach
or small intestine, this is not supported by my own findings or those of most other researchers. In fact,
Vitamin C supports selenium uptake by preventing the inhibitory action of zinc on selenium (making
Vitamin C synergistic to selenium instead), particularly when organic forms are used.
On a similar note, while sulfur and molybdenum compete for uptake in plants, supplementing either
one in humans helps uptake of the other by inhibiting copper, which is an antagonist to sulfur and
molybdenum, so for practical purposes (and confirmed in thousands of clinical applications), they work
as synergists with one another. There is an identical relationship between vanadium and selenium
against chromium, resulting in the same synergism.
Some people - because of media hype (more is better) - take several hundred mcg of selenium a day,
but I usually advise my own patients against higher amounts - not so much because of selenium toxicity
(although that does become a concern at higher amounts), but because of its antagonism to chromium,
zinc, magnesium, and other nutritional factors. Long-term excessive intake of selenium increases the
potential risk of triggering shingles, or developing trabecular osteoporosis"