Even if you’re not pregnant, you have to be worried about toxic mercury levels in fish.
Mercury is a highly reactive heavy metal that’s present in raw fish, like sushi, and in canned fish, like tuna. Exposure to toxic levels of can cause damage to the nervous system and the renal system, but long term exposure at lower levels hardens arteries by inactivating antioxidant mechanisms.
In fact, high mercury content can diminish the cardiovascular benefits of fish consumption, so eating fish may not benefit your health after all (Guallar et al, 2002, N Engl J Med).
So how safe is your sushi? More and more, it’s safe to assume your fish is polluted. The data coming in from a smartly conceived project called “Got Mercury?” from the non-profit watchdog group Turtle Island Restoration Network indicates that high-end restaurants in major US markets are serving tainted fish. The group is running a brilliant campaign to collect and test samples from some of the finest sushi parlors in Los Angeles, San Diego, and Chicago. A friend of mine in LA who frequents one of these places was tested as a result. She was in “sushi detox” when we last had dinner together. Later we learned she was trying to get pregnant, and she tested for mercury as a precaution.
Sushi fans, beware. What these studies have found is disturbing. More than 10% of tuna samples contain levels of mercury that shouldn’t be eaten by any consumer–man, woman, or child–because they exceed the FDA’s “actionable level” of mercury (1.0 ppm). Nearly 70% of sushi tuna samples collected exceed Illinois EPA’s special advisory threshold.
If you figure sushi chefs charging $25.00 a piece are more discriminating about their choice of fish than those charging $2.50, then the average consumer should be very concerned about tuna. I used the “Mercury calculator” at GotMercury’s website to learn that 6 oz. a week of my favorite albacore tuna brings me to 100% exposure.
Some canned tuna is also contaminated. Albacore tuna contains 3 times the mercury of chunk light (0.353 ppm vs. 0.118 ppm). However, cans of chunk light tuna usually contain skipjack tuna, a smaller species with lower average mercury levels. A Chicago Tribune investigation found that chunk-light canned tuna sometimes contains yellowfin tuna (0.325 ppm), but the cans are not labeled correctly. Know your tuna! Read the label before you buy.