On the green living site Care2, Dr. Michael Greger tries his level best to encourage pregnant women to stop eating canned tuna. He builds his case using a 2010 University of Nevada, Las Vegas (UNLV) study that examined mercury levels in the three major brands of canned tuna.
Following is a refresher for Dr. Greger because he clearly missed the facts the first time around:
Canned tuna, like all other commercial seafood fished from the ocean, contain trace amounts of naturally occurring methylmercury emitted largely from underwater volcanoes — not mercury emissions from coal-fired power plants. The latter unfortunately pollutes inland waterways (rivers, lakes and streams), which accounts for the mercury found in sport-caught fish.
The Environmental Protection Agency (EPA) has jurisdictional oversight of inland waterways and the fish therein, but not the oceans and not the commercial seafood caught offshore. The agency responsible for the safety of the seafood we purchase at our local store or eat at our favorite restaurant is under the purview of the Food and Drug Administration (FDA). In short — it’s misleading to apply EPA standards to commercial seafood.
Logically, this means that FDA guidelines apply to canned tuna. What the disputed UNLV study found, and what Dr. Greger didn’t disclose, is that the average mercury levels of all three brands were well below the FDA's reference dose for acceptable levels of mercury. Even still, pregnant women have nothing to worry about; the FDA builds in a 1,000% safety factor to ensure safety and assuage fears.
The bottom line is that not one case of mercury poisoning from the normal consumption of commercial seafood in the United States has ever been reported in peer reviewed scientific literature. Americans, especially pregnant women, don’t eat enough seafood as is. There is no way that increasing their seafood intake to the levels recommended by medical and government guidelines is going to result in any of the scary health problems described by Dr. Greger.