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Should You be Worried About Mercury in Fish?

Could the mercury in fish outweigh the health benefits?

By
Monica Reinagel, MS, LD/N, CNS
February 10, 2010
Episode #081

This week, I’m going to be talking about mercury in fish: who needs to worry about it, how much they need to worry about it, and the most productive ways to worry about it.

For more up-to-date information on healthy eating, check out my new guidebook, Nutrition Diva's Secrets for a Healthy Diet. Read a free chapter here.

Should You be Worried About Mercury in Fish?

Do you feel that you’ve been getting mixed messages about fish? On the one hand, we’re supposed to be eating more of it because it’s so good for you. The FDA and the American Heart Association recommend that fish be on the menu at least twice a week. On the other hand, they’ve issued warnings about fish that are high in mercury. So which is it? Do the benefits outweigh the risks? In general, yes.

Seafood is a good source of protein and important nutrients like selenium, iron, and zinc. The oils found in fish have unique benefits as well. Fish (and fish oils) are good for your heart, your brain, and even your mood. People who eat more fish live longer, healthier lives. The very latest research suggests that fish oil may even help slow the aging process.

There’s just one thing. Virtually all fish and shellfish contain mercury, which is basically a nerve poison. Fish are exposed to mercury the same way we are: through the foods they eat and exposure to environmental pollution. Some types of fish contain only trace amounts of mercury; others have a lot more.

Adult bodies can handle small amounts of mercury with no problem. Developing fetuses and small children, however, are much more sensitive to mercury—especially methylmercury, which is the form found in fish.

Should You Eat Fish During Pregnancy?

Exposure to mercury in the womb can cause serious and permanent damage to the developing nervous system. That’s why the FDA has issued advisories for pregnant and nursing women to limit their intake of all fish to two servings a week and to avoid fish known to be high in mercury altogether.

There are only a handful of commonly-eaten fish that are high in mercury. They include:

  • swordfish

  • king mackerel

  • orange roughy

  • certain kinds of tuna, including albacore (found in canned white tuna) and ahi (popular sushi fish)

Note, however, that pregnant women are still urged to eat two servings of low mercury fish every week. That’s because nutrients in fish and fish oil support healthy brain development.

Fish that are low in mercury include:

  • shrimp

  • salmon

  • crab

  • tilapia

  • perch

  • whitefish

  • and lots more!

The National Resources Defense Council has a handy wallet card that you can print out and carry with you to remind you which kinds of fish are safe for pregnant women, and in what amounts.

Pregnant and nursing women need to be careful. Everyone else can relax.

And what about the rest of us? For the most part, we can relax. Most cases of mercury toxicity are caused by occupational exposure or contaminated water. Mercury poisoning from eating too much fish is extremely rare—even in people who eat a lot of fish.

What Are Signs of Mercury Toxicity?

Signs of mercury toxicity—in case you’re wondering—can include tingling or numbness around your mouth, hearing loss, tunnel vision, or loss of coordination. Left untreated, mercury poisoning can lead to kidney failure.  That’s the bad news. The good news is that, in adults, toxic effects due to mercury exposure are usually completely reversible.

How Much Fish is Safe for Adults?

In addition to the “Mercury in Fish” wallet guide I mentioned above, the NRDC has a nifty calculator that lets you punch in your body weight and the amount and types of fish that you typically eat over the course of the week. The calculator will estimate whether your mercury intake from fish exceeds the safe limit set by the Environmental Protection Agency.

Again, let me put this in perspective. You’d have to be getting 30 to 70 times the EPA’s suggested daily limit for an extended period of time to be at even a low risk of mercury toxicity. Still, if you’ve been eating lunch at the all-you-can-eat sushi buffet every day for the last five years, it’s possible that you have been taking in mercury faster than your body can excrete it.

If you are concerned that you may have been overdoing it at the sushi bar—and now that I mention it, your lips have been tingling lately— the most effective way to reduce mercury levels in your body is simply to reduce your exposure.  Back off on the fish—in particular, the types that are high in mercury.  If you’re really worried, your doctor can do a blood or urine test to check your mercury burden.

But my quick and dirty tip is that no-one—even pregnant women—should stop eating fish because of concerns over mercury. On balance, fish is one of the healthiest foods you can eat. If you’re pregnant, nursing, have small children, or you eat a lot of fish, just use the resources listed below to be sure that you are choosing wisely.

Keep in Touch

If you have a suggestion for a future show topic or would like to find out about having me speak at your conference or school, send an email to nutrition@quickanddirtytips.com.

You can also post comments and questions on my Nutrition Diva Facebook Page or my Twitter.  I answer a lot of listener questions in my free weekly newsletter, so if you’ve sent a question my way, be sure you’re signed up to receive that.

Have a great week and remember to eat something good for me!

RESOURCES: 

Fish and Cellular Aging

Blood Mercury Levels and Fish Consumption 

Mercury in Fish Wallet Card (NRDC)

What You Need To Know About Mercury in Fish (FDA advisory)

Mercury Calculator
 

Fresh fish image courtesy of Shutterstock.

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