Sushi is Good For You... Except When It's Not

If you, as sushi lovers, are anything like me, you tend to look down your nose at the questionable looking Stop & Shop tuna rolls that sit in a sad display next to the fish counter. You prefer, instead, a more credible sushi restaurant. Unfortunately, a new study show that mercury levels in restaurant tuna sushi are higher than the tuna rolls at the supermarket.


Excess mercury levels in our fish is nothing new, Swordfish and Herring are known offenders. Mercury concentrations tend to be higher in species at the top of the food chain and those species at the top of the food chain tend to be bigger. This is a problem for sushi lovers since bluefin tuna can weigh over 500 kg.

Image from: Sealionsushi.com

The levels of mercury present in Tuna can cause severe neurological problems in humans. The US Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) recommend that pregnant women and young children limit they amount they consume. This advice is for general fish consumption, not just for sushi.

Also, studies show that there are different levels of mercury in different tuna species. Michael Gochfeld, a scientist from Rutgers University, did a study to find out which types of tuna hold the greatest amount of mercury. The team identified 100 sushi samples from 54 restaurants and 15 supermarkets using specific genetic markers to determine which species of tuna was in the roll.

The tuna sushi sold in restaurants had higher mercury concentrations than the sushi sold in supermarkets. Bigeye and bluefin tuna were more prevalent in restaurants and had mercury concentrations that approached or surpassed the FDA mercury limit of 1.0ppm. Yellowfin tuna is cheaper and is therefore more prevalent in supermarket sushi. It contains much less mercury than the bluefin tuna, but almost all of Gochfeld’s samples surpassed the EPA mercury limit (which is more conservative than the FDA limit). The mercury found in the samples of the bigeye and yellowfin tuna actually surpassed the FDA’s estimates of the amount of mercury contained in this fish.

Gochfeld warns sushi eaters that “If you’re going to eat sushi frequently, you should certainly stay away from tuna sushi, it should only be an occasional treat.”


Note to self: swap tonight’s tuna roll for a Philly roll instead.