Mercury Content By Fish — If You’re Crushing Canned Tuna, Ahi, Or Swordfish, You’re A Candidate For Mercury Poisoning
Fish is uber-healthy. It’s loaded with lean protein, vitamin B12, selenium (an antioxidant mineral), and heart-reinforcing omega-3 fatty acids (EPA + DHA).
The perks for a lean, strong body FAR outweigh the risks. But if you’re grilling fish or getting your sushi on regularly—and you absolutely should be—mercury is a very real concern, and something you should be cognizant of.
Canned tuna and swordfish, in particular, are a swimming toxic wasteland.
We’re on the verge of an impending heavy metal crisis. According to researchers at Harvard and the US Geological Society, mercury levels in the Pacific have jumped by 30% over the past 20 years, and they’re expected to rise another 50% by 2050.
Cool. But why does that matter from a health PoV?
Every time you eat fish you’re consuming mercury. It’s naturally laced with the stuff. Levels fluctuate massively based on location, pH, and the ecological food chain, but in general it works like this:
Mercury seeps into the environment from factories, manufacturing plants, coal mines, and even volcanoes. Once it gets into the water it’s converted into methylmercury (MM) by bacteria in the soil, which is eventually soaked up by tiny plants and other microorganisms.
Small fish live off those small organisms and start accumulating methylmercury. When bigger fish NOM the smaller fish their tissue gradually experiences major MM build-up. That cycle compounds up the food chain — that’s why large fish with long lifespans (mako shark, swordfish, and yes, tuna) are riskier in high quantities. They’re basically living off of mercury.
You are what you eat.
To put the variance into perspective, the FDA estimates that 6 oz. of salmon has ~.132 PPM of methylmercury. Compare that to the whopping 4.13 PPM in sushi-grade ahi tuna and 5.97 PPM in swordfish and the picture starts to get murky. That’s 31x and 45x, respectively, for the same amount of meat. Those numbers add up fast if you’re choosing the wrong fish in excess, and the effects can be massive.
“When you eat seafood containing methylmercury, more than 95 percent is absorbed, passing into your bloodstream. It can move throughout your body, where it can penetrate cells in any tissue or organ.”
Methylmercury directly enters the bloodstream. In high enough volume it can cause major damage to the brain and nervous system, most notably mercury poisoning. Symptoms include everything from pins and needles to loss of balance, brain fog, numbness, and coordination issues.
Don’t freak. Most of the good stuff is clean (enough) to the point that it’s a non-issue.
The Dirty 15 — 15 Fish with the Highest Mercury Content
Realistically, mercury isn’t so pervasive that it’ll impact the way you eat most fish. You can still slurp oysters until you’re in a full-blown aphrodisiac trance. But there are a few fish to limit as often as possible. Especially if you’re pregnant.
The FDA and EPA recommends that women and children completely cut out Swordfish, Gulf Tilefish, Shark, and King Mackerel. Swordfish is so bad that a 5 oz. cut packs 261% of the daily limit for mercury exposure (for a 170 lb person). Gulf tilefish pushes 380%. Consider all 4 off limits.
If you’re eating A LOT of fish—multiple times every week—try to limit everything in the top 15. Ahi tuna is the most depressing inclusion, especially for sushi connoisseurs who live off of it. On occasion it’s fine and I wouldn’t worry about removing it from your diet (I’m still eating it). But if you’re engulfing tuna rolls 2-3x per week, swap some of it out for salmon — it rolls in at .022 PPM per ounce.
But the most common offender—and the one that you’re probably eating WAY too much of—is canned albacore tuna. It’s the second most consumed fish in America, right behind shrimp, and accounts for 28% of all mercury exposure in America.
Image: Consumer Reports
For most people, ONE can of albacore per week will put you over the mercury limit. Chunk light is slightly less egregious, but there’s still roughly a 2 can cap. Some people down 5-10 cans per week. It’s not healthy as a primary protein source. So much so that Consumer Reports recommends that pregnant women don’t eat any.
Okay, So What Fish CAN I Eat Nonstop?
An entire ocean. Everything in the chart below is extremely low in mercury and safe to eat, even in high quantities (they’re all under .1PPM/oz).
Big fish like salmon, tilapia, trout, sole, and flounder make great options for whole cuts and fish tacos. Oysters, clams, scallops, squid, crab, shrimp, lobster and other shellfish are all low enough to the point where you shouldn’t even think about it.
Image: Consumer Reports
For a full list of mercury levels by fish type, check out the link over at FDA.gov.
ELLO ELLO I'm Bryan DiSanto.
I'm the Founder & Editor-in-Chief of Lean It UP
, a CPT/CSN/Fitness Coach, Chef trained at Le Cordon Bleu – Paris, NYU graduate, ex-fat kid
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