I came across this article on CBSnews.com today which discussed how our fish supply is becoming increasingly contaminated due to air pollution from Asia. The pollution is due to the coal burning plants common in India and China. Coal contains mercury which is released when it gets burned, releasing elemental mercury into the atmosphere. When rain falls, containing the mercury falls from the atmosphere, it lands in the oceans. Now, elemental mercury is not toxic, however, once the particles settle into the ocean, the elemental mercury is converted to methyl mercury by ocean bacteria, which is then eaten by marine species, such as fish. And then we eat the fish. When we eat fish, we are also eating the mercury that has accumulated in their tissues. Larger fish, like swordfish and tuna, have been shown to contain higher mercury levels than smaller fish, like sardines and salmon, because of something called bio-accumulation. Big fish eat the smaller fish, and the smaller fish eat the algae, which contains mercury. Even though larger fish may not eat mercury-containing algae, by consuming a large amount of small fish which have eaten the algae, the large fish accumulate all the mercury from the small fish they have eaten. All fish have mercury so it is recommend that we eat the smaller fish which are supposed to be lower in mercury and limit our intake of larger fish. Although we have known this information for a long time now thanks to researchers who have studied how mercury affects ocean life, newer studies have found that deep ocean levels of mercury will double by 2050 as industrialization in India and China continues to expand. This leads us to the question the safety of consuming any amount of fish at all.
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Chris Kresser recently interviewed Dr. Nicholas Ralston on his podcast, the Revolution Health Radio Show (read the transcript here). Dr. Ralston is a research scientist at the University of North Dakota Energy and Environmental Research Center evaluating potential human health effects and risks resulting from environmental exposure to air toxics. According to his research, so long as we are eating fish that have more selenium in relation to mercury, we should be in the clear. Selenium is needed for several enzymatic reactions that help to bind up mercury in our blood and prevent it from entering our tissues, so having adequate selenium should balance mercury intake.
Some key points to consider:
- Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish
- If a fish contains higher levels of selenium than mercury, it may be safe to eat
- Most species of commonly eaten fish in the U.S. have more selenium than mercury
So should I eat the fish, or not eat the fish?
I’m sure most consumers are just as confused on this issue as I was. A popular health recommendation recently has been to increase our consumption of wild caught fatty fish like salmon, mackerel, and sardines. On the one hand, you have doctors like Dr Weil, Dr Mercola, and Dr Lipman who hail wild caught salmon as a superfood and recommend that we should be consuming it weekly. On the opposite end of the spectrum, there are doctors who specialize in environmental medicine, a branch of medicine that looks at how environmental toxins can make us sick, who are now saying there is no longer any safe level of fish to consume due to toxic contamination of our lakes and oceans.
My approach so far has been to err on the side of moderation rather than take either of the extremist view points. I eat fatty fish, particularly wild salmon and even most shellfish but try to avoid the fish that are known to be more toxic. Here is a great pocket guide listing the best and worst choices.
What should I do about it?
The toxic effects of mercury include neurological impairments like tremors and memory loss, fatigue, hair loss, trouble thinking, muscle aches, headaches and a metallic taste in the mouth.
If you are concerned about your level of exposure to mercury, it would be best to see a doctor who specializes in environmental or functional medicine. These doctors are educated in the health effects of environmental toxin exposures and can test your body level of toxic heavy metals like mercury.