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Comment by nubbins | Hacker News Reader

High end omakase meals generally come with 1 or 2 .5 oz pieces of tuna. Even at 3x a day it would be comparable to one can of tuna. Of course mercury varies heavily from fish to fish but unless they were living on tuna/swordfish this sounds like an urban legend or could be something else in raw fish like liver parasites or bacteria.

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Sushi-grade tuna and I suspect tuna steaks are much more likely to be from the larger tuna species. At the very high end you get the special cases where truly massive fish are sold at auction for absurd prices - the same fish that got to that size by eating a huge number of smaller fish and thus concentrating mercury. Canned "solid" albacore or "white" tuna has the same issue, though I wouldn't be surprised if it was still lower than fish sold for sushi or steaks.

Chunk "light" tuna on the other hand tends to come from smaller species and pretty much as a direct consequence has lower mercury levels.

Based on the numbers in https://en.wikipedia.org/wiki/Mercury_in_fish, canned light tuna and skipjack have 1/3 to 1/2 the mercury found in albacore and yellowfin tuna and 1/4 the levels found in bigeye. Notably, those 3 all run 2-10x the size of the smaller species used in "chunk light."

> Even at 3x a day it would be comparable to one can of tuna.

The amount of mercury in the type of fatty tuna used for sushi is several times more mercury than in light canned tuna, which is normally what you'd use for a tuna melt or whatever.

Sushi grade tuna (unlike eel) isn't one of the types of fish you should never eat, but I definitely wouldn't eat it more than once a month.

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