By Brierley Wright, M.S., R.D., "Ask Brierley,"March/April 2012
A common concern when choosing seafood is mercury. And for good reason: mercury binds up selenium, an essential mineral that's vital to the developing brain and nervous system.
But here's the good news: eating ocean fish that contain more selenium than mercury protects against mercury toxicity.
Ocean fish (e.g., halibut, salmon) and shellfish (e.g., lobster, crab) are chock-full of the mineral: 17 of the top 25 selenium food sources are seafood (it's also in red meat, eggs and chicken).
The fact that most ocean fish are so high in selenium explains why more and more research suggests the benefits of eating seafood outweigh any risks mercury exposure could pose.
Bottom Line: Kids, women who are or could become pregnant and nursing women should follow the EPA's advice to avoid shark, swordfish, king mackerel and tilefish (they contain mercury levels that can be higher than or equal to selenium). But it appears to be unnecessary to limit albacore tuna to 6 ounces a week, says Nicholas Ralston, Ph.D., health effects research program leader at the University of North Dakota. "Like most varieties of ocean fish, tuna contain mercury, but provide far more selenium."