Are There 9.6 Billion Reasons We Should Fear Mercury In Fish?

Posted: 30/07/2013 in English, Science and stuff
Tags: , ,

Written by: Kevin Cann (web)

The Environmental Protection Agency (EPA) on July 5, 2006 launched the EPA’s Roadmap for Mercury.  This is an 87 page document that outlines the dangers of human consumption of mercury. This document can be viewed on the EPA’s website here, .  In a nutshell it explains the dangers associated with mercury consumption.  The primary form of mercury that humans are exposed to is methyl-mercury and fish consumption is the primary means in which people are exposed.

This government program is going to cost roughly $9.6 billion.  With the national deficit rising is this the best way for the government to be spending their people’s money?  The EPA cites research that shows methyl-mercury in humans can lead to liver, kidney, and immune system problems ( ).  About 95% of methyl-mercury is absorbed by the gastrointestinal tract and then deposited in various tissues throughout the body.  The mercury then may reside in the tissues for up to 50 days.

A major fear of the EPA is the levels of methyl-mercury that may come into contact with a fetus and a newborn baby.  The fear is that high levels of mercury may have effects on fetal development such as limb deformations and mental retardation.  The EPA’s Fourth Report cites studies that show in animals there is a greater amount of mercury in the cord blood when compared to the mother’s blood. There are also low concentrations of mercury found in breast milk with the transfer being greatest with the inorganic forms.  The report goes on to show research that shows the high levels of prenatal exposure to mercury lead to mental retardation and limb deformities with lower levels leading to a decline in cognitive testing in children.

The human studies are epidemiological.  This means they show a possible correlation, but not necessarily causation.  Also, the methods used to test for blood mercury levels (blood, urine, and hair) do not correlate well with serum levels ( ).  Does this mean that we should not be concerned about mercury?  The answer to that question is that we should be concerned.

Autopsies of humans with Alzheimer’s disease have shown increased levels of mercury in the brain, and in vitro the pathology of mercury exposure showed similarities to that seen in Alzheimer’s disease ( ).  The potential risks of mercury exposure are definitely something to be concerned about.  The problem with this research is it is short sighted and only looking at one thing: mercury exposure equals disease.  Could there have been other factors associated with the Alzheimer’s patients having higher levels of mercury in the brain?  The answer is yes.

Adequate levels of selenium actually protect us from the problems associated with mercury. In a study performed on rats the groups that had the high mercury and low selenium diets had the highest rates of growth impairments.  These impairments were predictable based on mercury to selenium ratios ( ).  Rats and humans do differ dramatically in some ways so how would this correlate to human metabolism?

Selenium’s protective effects against mercury happen in two ways.  First, a selenol group can actually bind to the mercury, and also selenium’s role in the body as an antioxidant actually protects us from the oxidative damage that mercury causes ( ).  The studies done on humans in this context have the same downfalls as the previous ones.  They are epidemiological and use testing methods that may not be ideal.  However, in this case the tests looked at the relationship between selenium and mercury.

In that previous study they looked at 72 subjects.  The mercury miners that showed higher levels of mercury exposure also showed higher concentrations of glutathione peroxidase and selenoprotein P.  The latter bound more mercury at higher mercury levels found in testing.  Glutathione is one of our body’s strongest antioxidants.  I wrote about glutathione in a previous article that can be read here, .

There are actually five selenium containing glutathione peroxidases.  They help protect us from oxidative damage.  Selenoprotein P (that the previous study mentions) is a transport protein for selenium, as well as an antioxidant.   A selenium deficiency actually leads to a decrease in glutathione peroxidases ( ).  This tells us a couple of things, for one mercury does lead to oxidative stress.  This is seen from the increase in glutathione and selenoproteins.  It also shows that we have a protection from the dangers of mercury.  Other studies have shown that selenium actually bonds to mercury as well ( ).

What these studies tell us is that we need more selenium then mercury to protect us from the damages associated with mercury.  This is for adequate glutathione production to protect us from oxidative damage, as well as enough selenium to bond with the mercury.  What are our best natural sources of selenium?  Brazil nuts, and ironically fish.  In fact the only fish shown to have more mercury then selenium is the Mako shark ( ). That means your tuna and salmon have more selenium then mercury, rendering the mercury harmless.  This is good because consuming fish 1-2 times per week showed a 36% decrease in cardiovascular disease and a 17% decrease in overall mortality ( ).

Mercury does lower our total selenium, and fish is not the only source of exposure.  The air we breathe, water we drink, and even dental fillings are all places we may be exposed to mercury. Replacing dental fillings that contain mercury with safer ones, drinking filtered water, and using air purifiers in your home are all ways to limit mercury exposure.  Also, stick to eating fish that contain higher levels of selenium then mercury.  There is a list known as the Selenium Health Benefit Value where you can look up the types of fish ( ).

Also, maintaining adequate levels of selenium.  The daily intake of selenium should be 200mcg.  An ounce of Brazil nuts contains 544mcg of selenium and a serving of tuna contains about 90mcg.  A couple Brazil nuts per day will allow for adequate selenium levels.  The mercury in vaccines is another big topic in media outlets and this information may even help you weigh the risk versus reward for those as well.

In conclusion, the government spending $9.6 billion to lower the mercury levels in fish is unnecessary.  Maintaining adequate levels of selenium can protect us from mercury toxicity by binding to mercury as well as protecting us from oxidative damage.  On top of that, the fish consumed by humans (except for the Mako shark and possibly some species of whales) contain more selenium than mercury.  This makes it safe to get all the positive health aspects associated from eating fish 1-2 times per week.


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