Safe to Eat? New Study Examines Mercury in Seafood

Database gives valuable information to consumers looking for answers.

swordfish
Predator species like swordfish (pictured) contain higher levels of mercury. (Photo: Digital Vision/Getty Images)
Clare Leschin-Hoar's stories on seafood and food politics have appeared in Scientific American, Eating Well and elsewhere.

The number one question we field when it comes to seafood is: “Is this fish okay for me to eat?” What folks really want to know is whether or not their fish sandwich comes from a fish that’s overfished or harvested in a harmful way; or if it is harboring scary containments like mercury or PCBs.

For those who fret over mercury contamination, a new paper published this week in Environmental Health Perspectives may demystify some concerns. The study takes a closer look at mercury levels in a variety of seafood and makes the database available to the public.

“The goal of the paper was to show people who create fish advisories that there’s a resource out there more comprehensive than the FDA database,” says Tim Fitzgerald, a scientist with the Environmental Defense Fund and co-author of the recent study. The database was also the basis of the seafood selector and mercury advisories put out by EDF and adopted by other groups like Seafood Watch.

“Now everyone can see the information—where we got the data from, where we didn’t, and why we made the choices we did,” he tells TakePart.

The report is timely. As we reported earlier this spring, Americans are not eating enough fish, and may be missing out on important health benefits. Why? In part, because worries over contamination may have scared them away.

Gavin Gibbons, spokesperson for the National Fisheries Institute, says the newly released study isn’t helpful to consumers, and that the net effect of eating fish as a whole food shows there’s a clear benefit to the heart and brain.

“Basically this study simply gathered a variety of mercury levels in fish and listed them. We’ve been down the path of crafting seafood advice based on just mercury or just omega-3s and that isn’t helpful because that isn’t how people eat fish,” he says, noting government dietary guidelines urge people to at least double the amount of fish they currently eat.

Many experts agree that if you eat seafood three or four times a week, it would be wise to vary the types of fish you select. After that, the advice can become muddled depending on the source. Dr. Nicholas Fisher, who studies mercury contamination in seafood at Stony Brook University and was a co-author of the new report, says it’s inappropriate to advise people to eat all the fish they want if it’s a species of fish known to be enriched with mercury.

“Different fish have different levels of mercury contamination,” he tells TakePart. “Upper-level predators like shark, some species of tuna (such as bluefin and albacore) have higher levels, as opposed to tilapia or salmon, which have much lower mercury levels. You can eat all the tilapia you want and show no signs of mercury contamination. That isn’t true for swordfish, bluefin, or marlin.”

What else gets the okay? Seafood like shrimp, mussels, clams, oysters, and flounder.

It’s also just the beginning of this type of study. Fisher says a number of reports and an epidemiological study on seafood consumption and mercury are in the pipeline, but cautions that science moves slowly. 

Are you afraid of mercury in fish? Are there any types of seafood you avoid?

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