Plenty of fuss has been made in the past few weeks over a New York Times investigation into the health risks of eating sushi, with tuna, and more specifically, bluefin tuna, painted as the biggest villan. The problem is the level of mercury in the fish, and mercury is a nasty neurotoxin. The fuss is over whether the risks of poisoning your brain outweighs the benefits to your heart from all those healthy omega-3 fats tuna offers. But there's another way to resolve the dilemma that seems to have been overlooked.
The New York Times public editor summarizes the tuna battle in a look at the challenges facing reporters covering a science story where the science isn't settled.
Researchers have concluded that mercury can harm the neurological development of young and unborn children. In 2004, the government urged pregnant women, women who might become pregnant, nursing mothers and young children to eat no more than 12 ounces a week of fish known to be low in mercury and to avoid some fish altogether, though not tuna. Freydkin, who is 35 and thinking about children, is right in the target audience, and The Times performed a service for her.
But what about the rest of us? The day after the article appeared, Time.com asked a Harvard epidemiologist if people should stop eating tuna. "No," said the doctor, Dariush Mozaffarian. "Over all, the dangers of not eating fish (including tuna) outweigh the small possible dangers from mercury" for healthy adults who eat the recommended one or two servings a week. He stressed the benefits of the fatty acids in fish that appear to help prevent heart disease.
For adults not in the target group for the government's advisory, the effects of mercury at the levels found in The Times's tests are not clear.
Bluefin tuna (Thunnus maccoyii and Thunnus thynnus, depending which ocean your ultimate supplier is fishing) had the highest levels of mercury, and the blood of one reporter who ate sushi three times a week had a mercury reading 150 percent higher than normal. Yikes. So is that really bad enough to warrant cutting tuna out of your diet?
The first thing to know is that other surveys have produced less worrisome numbers. But given the possible danger to pregnant and nursing mothers, it's probably wise that at least that particular demographic avoid tuna, at least until the science is more certain.
The second thing is not all tuna are the same. You can spend the time researching the difference between the various canned varieties (albacore, yellowfin, skipjack, white and light), but not all tuna is labeled in a consistent manner. If we're just worried about bluefin, however, we can restrict our discussion to tuna steaks and sushi.
The third thing, and to my mind, the most important factor to consider is that bluefin tuna populations aren't doing particularly well, to put it mildly. According to the IUCN Red List, which is pretty much the most authoritative source for this sort of thing, some stocks are endangered, at least one is critically endangered, we don't have enough data for others, and those estimates that do have solid numbers are getting old.
The last time anyone supplied a comprehensive population survey of the Northern bluefin tuna of the Atlantic, for example, was in 1996 (by Carl Safina). And what did we get: the species is listed as data deficient and out of date.
As a result, environmentalist warn that "the species is nearing commercial and ecological extinction." (Reuters, March 1, 2007) and regulators are finally starting to pay attention.
In fact, for the past four years European Union officials have set catch quotas at nearly double the levels their scientists recommended, and fishermen have exceeded those already-elevated quotas by 50 percent each year. (Washington Post, Dec. 24, 2007)
Acting to curtail over-fishing and dwindling stocks, the European Commission today banned fishing for endangered bluefin tuna in the eastern Atlantic and Mediterranean for the rest of the year. Officials said the move was aimed at preventing under-reporting of catches, which results in over-fishing. France is one of the biggest offenders. (USA Today, Sept. 19, 2007)
So it really doesn't matter how much you like your tuna sashimi. If we don't stop chowing eating bluefins (I'm talking to you, Japan, consumers of 80 percent of the catch), the problem of whether it's good or bad for you will be moot.
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and you can add just about every other ocean caught fish species to the list as well. Everything has been grossly over fished. No one should be eating anything other than land farmed fish (ocean farming, at least for salmon, is having disastrous impacts on wild salmon due to sea lice infestations)
You can obtain omega-3 fatty acids from a variety of sources that carry a much smaller risk of heavy metal contamination. I suspect the fat thing is mostly an excuse used by people who want to justify their love of seafood.
And, of course, yes, pretty much everything's endangered at this point.
Actually, if those mercury levels really are harmful to developing fetuses, that should show up in Japan, where people eat a lot of fatty fish (not just tuna), and pregnant mothers are advised to increase their consumption. If there isn't a significant difference in birth defects or developmental disorders associated with mercury, then it becomes hard to argue that there could be any practical harm in those levels.
As for tuna itself, bluefin is expensive - not something most people here would regard as a staple diet - and it's only been embraced as a sushi topping only fairly recently (it used to be seen as too bland to make for good sashimi with sushi).
Bluefin consumption has decreased in Japan from what I've read, but that has been more than compensated by the increased popularity of sushi in the rest of the world, compoundeed by the mistaken belief that tuna is the most common or most important fish to serve with sushi. Our local sushi restaurant has a menu of well over fifty different kinds of nigiri-sushi (pillow of sushi with something on top); two of those are maguro (bluefin tuna), and they're only two because different cuts are served separately, at different prices. I go to sushi in Europe on the other hand, and tuna is presented as the centerpiece.
To say "pretty much everything" is overfished or endangered is not accurate. Go to Seafood Watch if you care to bother your minds with actual information.
http://www.mbayaq.org/cr/seafoodwatch.asp
MP-
Thanks for the link.
This begs the question of whether h. sapiens is sustainable!
Are there any Malthusian tipping points on the horizon?
Perhaps we need a reliable assessment of the footprints of all of our endeavors. The 'usual suspects' will deny any probabilities because "god" is in control. Besides, footprint accounting and responsibility will cost 'em money.
Nice information Thanks for sharing