If you've been worrying eating fish because of the risk of mercury toxicity from eating too much seafood, I have some good news for you. Luckily, there's a mercury-selenium connection that may wash away your fish-eating fears.
Current U.S. recommendations from the Environmental Protection Agency suggest that women who are trying to conceive, pregnant, or nursing – as well as children – should avoid shark, swordfish, king mackerel, and tilefish which contain high levels of mercury; limit consumption of low mercury fish to 12 ounces per week, and further limit locally caught fish to less than 6 ounces per week just in case it might be high in mercury.
The main study that triggered these recommendations about avoiding mercury in fish followed 1022 children born in the Faroe Islands of Denmark in the late 1980's. The study examined correlations of mercury in umbilical cord blood and test scores of those children at age 7. The study concluded that prenatal exposure to mercury correlated to lower IQ in offspring. (source)
It's important to note that some members of the Faroe Island community ate large amounts of pilot whale, a species which contains extremely high levels of mercury – 25 times the amount commonly found in tuna. (source and source) Turns out that whale also happen to be low in a mineral called selenium. Which brings us to…
The mercury selenium connection
While mercury toxicity is definitely something any human should aim to avoid, newer evidence shows that there is a missing piece to the mercury warnings that makes them much less scary.
Selenium counteracts the effects of mercury by binding to it and making a new substance that then allows mercury to pass out of the body without binding to human tissue and wreaking havoc. Because of the strong affinity that selenium and mercury have for each other, as long as selenium is present in higher quantities than mercury, you are most likely safe to consume fish. (source)
Lucky for fish lovers, many of the fish that are high in mercury are also higher in selenium – with shark and swordfish being the two fish known to be consistently low in selenium.
The moral of the story is that most fish contain more selenium than mercury, so they are unlikely to poison you with mercury.
If you’re still concerned about mercury toxicity, you might consider taking a selenium supplement, especially if you frequently consume swordfish or shark.
With the protection of selenium you can enjoy the culinary delights and nutritional benefits of seafood without a big side of worry.
Woo hoo! I don't know about you, I'm super stoked that I don't have to fret about mercury poisoning from fish.
Who's ready for some sushi?!