Mercury. In the form of methylmercury, it is a very harmful biological toxin. It is a threat to our brains and nervous systems and our livers and our kidneys. Too much exposure to methylmercury is likely to cause brain damage and nerve damage.
Fortunately, selenium supplements can help. And they do help. The relationship of mercury and selenium is a story with an ironic twist. To the extent that selenium binds with mercury in the body and de-toxifies the mercury – a very good thing for us – to that extent the body is robbed of selenium that could be used for the production of beneficial selenoproteins with other important biological functions.
Protecting us against the toxic effects of mercury means fewer selenoproteins to act as antioxidants neutralizing harmful free radicals, fewer selenoproteins to strengthen immune system function and thyroid function, and fewer selenoproteins to help reduce the risk of cancer.
Let’s take a closer look at the relationship between mercury and selenium.
Where does the mercury come from?
Our exposure to mercury comes from a variety of sources:
- additives in processed foods
- fish and seafood
- industrial pollution (coal plants, cement plants, and pulp and paper plants, for example)
- leakage of mercury vapor from amalgam fillings in our teeth
What does the selenium do?
Mercury, left to itself, binds strongly to fatty tissue in the body. It accumulates in the tissues and organs and ties up receptors that should be available for essential vitamins and minerals and other nutrients.
Mercury, fortunately, is strongly attracted to selenium and will make a strong bond with selenium compounds.
This bond between mercury and selenium will neutralize the reactivity of the mercury. Furthermore, the mercury and selenium complex that is formed will not be absorbed by the body. The body will eliminate the mercury and selenium complex.
Depletion of selenium stores in the body
It is, of course, a very good thing for us that the mercury and the selenium are attracted to one another and form strong bonds before the mercury can be absorbed in fatty tissues where it can do us harm.
But, you can see, the necessary consequence of binding mercury tightly to selenium is the depletion of the available selenium in the body. There is less selenium for forming selenoproteins for other essential biological functions:
- antioxidant protection
- anti-inflammation protection
- anti-viral protection
- cancer prevention and protection
- successful fertility and reproduction
- thyroid regulation
Need to maintain a surplus of selenium
Who needs a good selenium supplement?
- those of us who have amalgam fillings
- those of us who like to eat fish
- those of us who are exposed to industrial pollution
I repeat myself: it is a great irony that protection against the toxicity of methylmercury – a good thing – is accompanied by a depletion of our bodies’ selenium stores – not a good thing.
Mercury and selenium in fish
Fish are not just known sources of mercury. Fish and shell fish are also a good source of selenium. But the two elements cancel one another out by combining together.
Studies have shown that many fish actually contain as much or more selenium as mercury [Ralston]. This may be true of salmon, for example.
It is not likely to be true of pilot whale, tarpon, shark, king mackerel, and tilefish, however. So, caution is needed.
It is not without good reason that the Environmental Protection Agency and the Food and Drug Administration have issued a joint advisory about the danger of mercury concentrations in fish.
It is not without good reason that women are warned not to eat too much tuna during pregnancy. Increased mercury absorption has been associated with reduced IQ levels in children.
A further word about mercury and dental fillings
Fortunately, the use of amalgam fillings is on the decline, but there are still many people who have amalgam fillings. The danger is that chewing and brushing could result in the slipping out of mercury vapor from the fillings. The mercury vapor would likely be absorbed in the lung tissue and other tissue.
To test the hypothesis that mercury vapor from amalgam fillings can be dangerous, Dr. Magnus Nylander and a team of researchers measured the concentrations of mercury in autopsy samples of human brains and kidneys. Their data showed that people with more amalgam fillings had had higher mercury concentrations. People with no amalgam fillings had lower mercury concentrations [Nylander].
Similarly, a study comparing blood and urine samples from dental personnel who regularly handled amalgam materials with blood and urine samples from matched control individuals showed higher mercury concentrations in the dental personnel’s urine and blood [Akesson].
Replacing amalgam fillings
Some people are asking the dentist to replace their amalgam fillings with composite fillings. If you are considering doing so, please talk to your dentist about taking selenium supplements in the period prior to, during, and following the dental work.
If there is mercury vapor slipping out into your mouth and lung tissues during the replacement, you want to have an adequate reserve of selenium to neutralize the mercury, isn’t that right?
Clinical trial results: selenium and mercury
At least two clinical studies have investigated the effect of selenium supplementation on the accumulation of mercury in the body.
The study data showed that supplementation with 100 micrograms of a yeast-based selenium preparation daily for four months resulted in significant increases in serum selenium levels and in significantly reduced levels of accumulated mercury [Seppänen].
The results of a three-month study in which the active treatment group received 100 micrograms daily of a patented organic SelenoPrecise® high-selenium yeast preparation showed significantly increased elimination of mercury (in the urine) and significantly reduced levels of bio-markers of oxidative stress [Li].
The bottom line on mercury and selenium
What does the current state of research say to us?
We should not be afraid to eat fish as a regular component of our diets. The omega-3 fatty acids in fish are beneficial to our health. However, we should ensure that we have adequate intakes of dietary and supplemental selenium to counteract the mercury that is in fish.
If we have amalgam fillings, we want to make sure we have adequate intakes of selenium to capture the mercury vapor that may be escaping from the fillings. And, if we choose to have our amalgam fillings replaced, we need to think about taking a good selenium supplement.
Those of us who live near coal plants, cement plants, and other plants that might possibly release mercury into the air or water will want to take care to get adequate amounts of selenium in our diets.
The greater our exposure to mercury is, the greater is our need for selenium supplementation.
Li, Y., Dong, Z., Chen, C., Li, B., Gao, Y., Qu, L., & Chai, Z. (2012). Organic selenium supplementation increases mercury excretion and decreases oxidative damage in long-term mercury-exposed residents from Wanshan, China. Environmental Science & Technology, 46(20), 11313-11318.
Nylander, M., Friberg, L., & Lind, B. (1987). Mercury concentrations in the human brain and kidneys in relation to exposure from dental amalgam fillings. Swedish Dental Journal, 11(5), 179-187.
Ralston, N.V. & Raymond, L.J. (2010). Dietary selenium’s protective effects against methylmercury toxicity. Toxicology, 278(1), 112-23.
Seppänen, K., Kantola, M., Laatikainen, R., Nyyssönen, K., Valkonen, V. P., Kaarlöpp, V., & Salonen, J. T. (2000). Effect of supplementation with organic selenium on mercury status as measured by mercury in pubic hair. Journal of Trace Elements in Medicine and Biology, 14(2), 84-87.
Disclaimer: The information presented in this review article is not intended as medical advice and should not be used as such.