5 Things You Need to Know About Mercury

April 11, 2014

We’ve all heard about the risks of eating certain types of fish. Here are the top 5 things you need to know about mercury and fish...

We’ve all heard about the risks of eating certain types of fish. So SupermarketGuru wanted to give you the five things you need to know about mercury and fish.

Where does it come from? Mercury in ocean fish comes from natural and human sources. About two-thirds of each year's new mercury comes from human sources, especially coal combustion. Mercury is an impurity in coal.  From the air it falls into water where bacteria convert it to a form called methylmercury that gets into living things and over time builds up. Plankton with mercury get eaten by little fish, and little fish get eaten by bigger fish. A big fish has gotten a dose of mercury from every little fish it's ever eaten. If you eat it, it will pass that combined dose on to you. Mercury accumulates up the food chain.

What fish have the highest levels? Among commonly consumed fish and shellfish, some have 100 times more mercury than other kinds. The highest levels are found in larger, longer-lived predatory fish such as shark, swordfish, tuna, marlin, and grouper, tilefish, and some mackerel.

What are the risks of too much mercury? Methylmercury harms the nervous system to differing degrees depending on how much mercury is involved. The dose you get depends on two things: how much mercury is in the fish you eat, and how often you eat fish. One meal of high-mercury fish isn't going to do it, but lots of continual eating of moderate-mercury fish can cause your mercury level to rise and cause problems.

What fish are safe? Low-mercury fish and shellfish include, salmon, shrimp, tilapia, clams, mussels, scallops, oysters, sardines, trout, pollock, flounder, sole, catfish, squid, anchovies and herring. Check out the Monterey Bay Aquarium’s Seafood Watch list for region specific best picks.

How do I know if I have high mercury? Ask your doctor to test you for heavy metals, including mercury. It’s thought that dark leafy green foods including cilantro and chlorella are able to help draw mercury out of the body. Now that you are armed with the facts, you can enjoy seafood often and keep your mercury exposure very low.

Blue Ocean Institute
Monterey Bay Aquarium Seafood Watch