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Selenium protects against mercury – provided you get enough

Selenium protects against mercury – provided you get enoughWe all get exposed to mercury, a neurotoxin that is found to a great extent in nature and in our environment. According to an EU report, mercury is a large economic burden to society because of the costs related to lowered IQ levels. For that reason alone, we should aim to limit our exposure to mercury and also take a closer look at how selenium protects against the harmful heavy metal – provided our selenium levels are adequately high.

When it comes to mercury, leading Danish scientists such as the two environmental toxicologists, Philippe Grandjean and Lisbeth E. Knudsen, call for lower threshold levels and more warnings. Mercury is able to cause an array of harmful effects, and fetuses are particularly vulnerable due to the development of the brain. Danish and British research suggests that mercury increases the risk of permanent brain damage in 25% of all children. This type of brain damage is not necessarily noticeable, yet it impairs the mental skills of those affected. The researchers discourage pregnant women in particular from eating predatory fish like tuna.

Mercury sources

  • Fish (especially predatory fish like tuna)
  • Amalgam fillings and wastewater from dental clinics
  • Vaccines (thimerosal)
  • Burning of coal
  • Incinerators, crematoriums, and church yards
  • Gold mining (mercury vapors are spread globally)
  • Electric bulbs, thermometers, and other types of measuring equipment

Why is mercury so dangerous?

Mercury generates free radicals and inhibits the trace element selenium that is an integral part of around 30 essential selenoproteins. Because of that, mercury is able to inflict serious damage upon our cardiovascular system, brain, nervous system, thyroid gland, and other tissues that are dependent on various selenoproteins. Mercury gets stored in the organs and is able to cross the blood-brain barrier. Fetuses are particularly vulnerable, as their cell division is enormous, and because selenium has vital influence on the development of the brain and nervous system.

Typical symptoms of mercury poisoning (where all other factors are excluded)

  • Lower IQ (especially if the mother has been poisoned during her pregnancy)
  • Metabolic disorders
  • Abnormal fatigue
  • Depression and anxiety
  • Headache
  • Poor concentration
  • Muscle and joint pain
  • Frequent infections and inflammation
  • Metallic taste in the mouth and periodontal disease

The higher the mercury exposure, the more selenium is needed to avoid poisoning

The selenium compound selenide binds mercury by forming mercury selenide, which neutralizes the harmful effect of mercury. However, once that bond is made, selenium is no longer available to react with the selenoproteins that depend on it. In other words, mercury increases our need for selenium, as we need selenium both to neutralize the dangerous heavy metal and to support the many essential selenoproteins at the same time.
A Chinese study showed that selenium yeast with many different selenium compounds effectively binds mercury. In China, researchers are aware of the problems with massive pollution and are currently investigating if selenium yeast can possibly help protect the Chinese population.

Selenium protects the thyroid gland and other tissues against free radicals

Mercury gets stored in the thyroid gland, among other places, which may increase the risk of both too low and elevated metabolism. This is a result of mercury inhibiting those selenoproteins that convert passive T4 thyroid hormone into active T3 thyroid hormone.
Other selenoproteins work as antioxidants that protect the thyroid gland against free radicals and inflammation. A Nordic report of dentists’ exposure to mercury mentions that people with low selenium status are more vulnerable when it comes to mercury and its harmful effect on thyroid hormones and the kidneys.

Selenium counteracts mercury accumulation

An American study of mice reveals that selenium supplementation may prevent mercury from accumulating in nerve cells, thereby limiting dysfunctions of the nervous system and muscles which are early signs of a poisoning. Selenium supplementation improved the animals’ running skills, their lifespan increased, and this discovery may have significant clinical importance. Based on their observations, the researchers concluded that selenium helps prevent mercury poisoning and has no side effects.

Purified fish oil for the brain and IQ of your child

Health authorities worldwide have increased their warnings to pregnant women when it comes to consumption of tuna and other types of predatory fish. Then again, it is exactly this type of fish that contains the most EPA and DHA, which are important for the development of brain and intelligence in children and have numerous other essential functions throughout all phases of life. Pregnant women and others who want to increase their EPA/DHA intake can opt for high-quality fish oils but should stick with products that are purified and contain extremely low levels (or none at all) of heavy metals.

More official information

Besides the common warnings against overconsuming predatory fish (especially if you are pregnant), we need more official information about how selenium can counteract mercury toxicity. This knowledge has been available since the 1960s and documented in mammals, birds, and fish – but we humans need to benefit from it as well.

Selenium protects against other heavy metals

Selenium has the potential to bind to various toxic heavy metals, including cadmium that is found in polluted air and tobacco smoke. Cadmium gets stored in the kidneys, and breathing cadmium-polluted air and smoke increases the risk of lung cancer in particular.
Selenium is also able to bind to the environmental toxin, arsenic, that is found in pesticides and polluted groundwater, among other things.
In other words, our need for selenium increases in step with our exposure to various environmental toxins.

Warning to smokers

Every day, smokers breathe in large amounts of cadmium and other harmful toxins. They should therefore make sure to get adequate amounts of selenium – both so they can avoid poisoning and oxidative stress caused by free radicals.

Compensating for the reduced selenium intake

European soil is generally low in selenium. This combined with low consumption of fish and organ meat contributes to our reduced selenium intake. Most Europeans fail to get the recommended daily allowance for selenium (50-70 microgram/day). In contrast, the selenium intake in countries such as the United States and Japan is naturally high, in many cases reaching as much as 200 micrograms daily. This is because selenium levels in the soil in these parts of the world are much higher.
Selenium supplements may compensate for the low selenium intake and help the body with detoxification (mercury and other environmental toxins). Supplements based on selenium yeast with many different selenium compounds provide a selenium intake that is similar to that which you get from eating a selenium-rich and varied diet.


DR-dokumentar: De ufødte børn 03-11-2014

Niels Hertz: Selen – et livsvigtigt spormineral. Ny Videnskab 2002

Heath, J.C. et al: Dietary selenium protects against selected signs of aging and methylmercury exposure. Neurotoxicology, 2010; 31 (2): 169-79

Fødevarestyrelsen: Råd om mad og motion. Når du er gravid

Njord, V Svendsen: Næringsstoffer i fisk neutraliserer miljøgifte. 2012

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