High mercury levels in tuna

[smallworld]

Has everyone read the New York Times article about toxic levels of mercury in tuna purchased in New York? The article is here (free registration may be required), and there is already a thread about it on eGullet here.

The article is specific to New York, but considering they get their tunas from many of the same places we do, I think this is worth discussing in the Japan forum as well.

I'm really surprised that there is so little discussion in Japan, both in the media and in general, about toxins in food. Especially in seafood like tuna, whale and hijiki (there was a thread about arsenic in hijiki a few years ago but I can't find it). Given that the high levels are well known, as are the ill effects of said high levels (or has everyone forgotten Minamata), the lack of information, debate and government control is troubling.

What are your thoughts about the issue, and do you have any insights on the apparent lack of interest in the subject here in Japan?

Personally, for the past few years I've been eating far less tuna than I used to, due to concerns about both overfishing and mercury levels. I still eat it occasionally but it's a treat. I haven't had kajiki (swordfish) for years, and I don't like whale much to begin with so that's not a problem. Thank god there are so many other fish to choose from (but I still miss tuna and swordfish).

[sanrensho]

do you have any insights on the apparent lack of interest in the subject here in Japan?

I'm going to say it's due to consumer apathy, bred by the general Japanese emphasis on moderation in diet. ("It won't kill me since I don't eat it every day.")

I'm willing to bet that many Japanese are at least aware of the issue, but not to the extent of significantly dissuading consumption. However, I think it would only take some well-placed media coverage to generate a significant public reaction on this issue (think "expose" style reporting).

On the other hand, I think the level of emphasis on organic/pesticide-free foods is about the same as in North America. Am I wrong?

Edited January 25, 2008 by sanrensho (log)

[helenjp]

There are several reasons for current attitudes to the issue of methyl-mercury in seafood in Japan.

First off, I thought this was a good general summary of advice people can expect to get in Japan:

All about guide to diet in pregnancy

The issue of methyl mercury in seafood is on the second screenful of the web-page. It starts by saying that fish is a wonderful source of protein, and has plenty of the omega-3 fatty acids helpful for babies' brain development. But some fish contain a lot of methyl mercury, so we should be careful. It has been said that excessive mercury may damage babies' nervous systems. And readers are referred to a link to the Ministry of Health, Labour, and Welfare website.

So there is some awareness, and the information on how much of which fish are safe to eat is there, but you have to dig for it.

The guidelines given by the MHLW site (look to be from 2005?) are:

up to 80g bottlenose dolphin (bandou-iruka) once every 2 months (10g per week, which is less than a 15g slice atop a single piece of sushi)

up to 80g short-finned pilot whale (kobire-gondou) once every fortnight (40g per week)

up to 80g per week of these fish:

a type of alfonsino (kinmedai)

swordfish (mekajiki)

bluefin tuna (kuro-maguro, hon-maguro)

bigeye tuna (mebachi-maguro, bachi-maguro)

a type of Japanese ivory shell/babylonia (etchuu bai-gai)

Baird's beaked whale (tsuchi-kujira)

sperm whale (makkou-kujira)

up to 80g twice weekly of these fish:

yellowback seabream (kidai)

striped marlin (makajiki)

a type of scorpionfish (yume-kasago)

southern bluefin tuna (minami-maguro, Indo-maguro)

blue shark (yoshikiri-zame)

dall's porpoise (ishi-iruka)

No concern if the following types of tuna are eaten in normal amounts so eat in a balanced way:

yellowfin tuna (kihada-maguro)

albacore tuna (bin-naga- or binchou- maguro)

young bluefin tuna (meji-maguro)

canned tuna

Notes:

Slice on top of one piece of sushi - 15g

serving of sashimi, slice of fish (small modern slice, in my experience) - 80g

Guidelines assume that the average weight of a woman entering pregnancy is just over 55 kg (120 lbs).

Only pregnant women are considered at risk - on the basis that half of methyl mercury is eliminated within 70 days of consumption, so a woman who starts to restrict high-mercury seafoods once she realizes she is pregnant will have reduced mercury levels by the major period of fetal brain growth in late pregnancy.

Regarding salmon, cod, shrimp/prawns, which have recommended limits in other countries: testing of these fish sold in Japan found low mercury contents, and no need to limit consumption was felt. Low mercury contents of around half the daily recommended limit are not subject to recommendations.

Tuna was included in these guidelines in 2005, because tolerable weekly/daily intake recommendations were lowered, and because a study of popular dishes such as donburi-style sushi topped with tuna use quite large amounts of tuna.

There is a further link to a MHLW table (in Japanese) with Mercury levels in around 400 varieties of fish available in Japan. This appears to date from 2005, and it seems that before this, information on mercury levels in tuna and was not easily available. The official explanation is that they were originally luxury fish and not part of the average person's diet.

It is also worth noting that quite a few of the species in the "recommend restrictions" list are commercial species, so people may not realize what they are eating in take-out, semi-prepared, or casual restaurant meals. Japanese food sites such as food co-ops also note that purchases of "whale" may actually be the higher-mercury-content dolphin species.

There have indeed been "expose" style reports, such as this background piece to an NTV report from 2003.

It is worth reading if you read Japanese.

The comments here and on personal blogs indicate that availability of information and policies have changed in the last 3-5 years. Since the Food Safety Commission was formed in 2003, as part of the Cabinet Office, this is where recommendations are generated. Note that the English site below includes an English document on methyl mercury policy, but I think it's about 2 steps behind the current policy. To find references in Japanese, you have to click the "risk assessment" button and search for methyl mercury and fish from there.

Food Safety Commission's English website

[JasonTrue]

The Specialty Food News mailing list that I subscribe to linked to this reaction from the ministry of health.

"But there is no doubt that mercury intake is harmful, and eventually destroys brain tissues," Ekino said, citing symptoms of Minamata victims, whom he has studied. "We should cut down tuna consumption to as little as possible."

The New York Times, in a story published Thursday, reported that eight of 44 pieces of sushi sampled from local restaurants and stores had mercury concentrations over 1 ppm, a level the paper reported would allow the U.S. Food and Drug Administration to take the fish off the market.

Ejima said the most dangerous thing he took from the report was that it could spread "groundless rumors."

"Seafood is an important source of nutrition," he added.

[MomOfLittleFoodies]

I was reading something, I think it was on the Monterey Bay Aquarium website, saying that the larger tuna are more of a risk mercury wise because they've had longer to accumulate methyl mercury in their tissues.

[Katie Meadow]

It's very interesting to hear from some people in Japan. The day of the NYT article the Japan Fisheries was very quick to publish a refutation of the amounts and effects of mercury in their tuna. Certainly the Japanese have major experience with methyl mercury disasters--Minamata, as mentioned above, and one other as well. Until I looked it up this afternoon I couldn't believe that mercury was pumped into the wastewater for more than 30 years and that over 2,200 people in the minamata area were diagnosed with mercury poisoning.

I guess I have a very cynical viewpoint. Should I not assume that the more the Japanese and others overfish bluefin tuna the higher the price they get per pound? Get it while the getting's good.

Yes, big tuna have more mercury than small fish; toxic metals build up in the system. I guess that's why the site quoted above by helenjp suggests that eating "young bluefin tuna" is fine. Of course their risk assessment is pretty lax, since they don't see a problem with albacore, either. My understanding is that when it comes to canned tuna, that's why chunk light is preferable to white or Albacore--because it is from smaller fish.

I like that Monterey Bay Aquarium site. It offers lots of clear information and is well organized with re to different ways of evaluating health and/or environmental risk.

[Ohba]

I guess I have a very cynical viewpoint. Should I not assume that the more the Japanese and others overfish bluefin tuna the higher the price they get per pound?

You already have, in the other thread, which is a much better place for it.

[budrichard]

If my menory serves me correctly, there was a swordfish 'scare' about 1970 in the US but after testing museum specimens, the consensus was that the levels had always been high. I found this reference for Tuna http://www.youngsseafood.co.uk/web/cr_policy_html.asp?id=12 but don't have a link to the actual study.

It may be that these large similar species have always had a high mercury content but that doesn't mean the mercury poisoning in not a serious affair.

The best is to be moderate in your consumption and limit consumption for the young and pregnant females.-Dick

[smallworld]

Thanks for the replies and links.

Only pregnant women are considered at risk - on the basis that half of methyl mercury is eliminated within 70 days of consumption, so a woman who starts to restrict high-mercury seafoods once she realizes she is pregnant will have reduced mercury levels by the major period of fetal brain growth in late pregnancy.

Helen, I'm not sure if you're quoting from the site you linked here or not, but this is just wrong. The 70 day elimination is for non-pregnant folks, while pregnant women eliminate mercury at twice that rate-- it goes straight to the fetus. In Minamata young mothers mostly escaped harm as their bodies fed all the mercury to the baby-- one of the saddest effects of Minamata disease was the high incidence of miscarriage (we will never know how many, as miscarriages weren't always recorded, especially before the disease was acknowledged).

Also, the third and fourth months of pregnancy are considered to be the most dangerous time, when both the developing brain and nervous system are vulnerable, but mercury can be a danger from conception until childhood. So only cautioning pregnant women is irresponsible, and widening the at-risk group to include all young children and women of childbearing age would make much better sense. Equally irresponsible is the notion that a woman can simply reduce her consumption of high mercury fish once she discovers she is pregnant, since plenty of women take a few months to realize they are pregnant.

Jason, thanks for the article. I'd be interested to hear what Yuichiro Ejima, the health ministry official in charge of food safety (of the "groundless rumours" quote) has to say about the current gyoza scare.

Budrichard, I wasn't sure if the mercury found in large fish and whales is naturally occurring (like the arsenic in hijiki, another seafood I'm avoiding) or the result of pollution. It's interesting to hear that swordfish and tuna may always have been high in mercury, but I can't help but suspect that the current high levels of mercury in tuna are at least partly due to man-made pollution. I wonder if there is any study of mercury levels in tuna from different parts of the world; perhaps a regional comparison would help clear things up.

[helenjp]

I'm not sure if you're quoting

Yes, my whole post was pretty much either quoting or summarizing from the linked sources, sorry if I didn't show that clearly.

I wanted to do two things - show what issues are being discussed by Japanese consumers, and also show what kind of information is available to the averagely curious consumer.

I'd be interested to hear what other coastal and island East Asian and Southeast Asian countries are saying on this issue, because the impression I get is that there is quite an east:west divide regarding the safety of wild fish.

As you say, the information and conclusions are quite different from current western recommendations (though the "official" recommendations vary even among western countries).

On the one hand, most food-safety coverage in Japanese media appears to concentrate on individual companies; rarely does anybody take on on entire industries - the dioxin and endocrine disrupters fuss is probably all but forgotten by most people, and it's quite possible that mercury issues could go the same way.

Let's hope that we see more information made available - and it would be great if people who are aware of useful resources in Japanese or English would post about them.

On the other hand, it is true that a big swing away from fish in a country with little agrarian land would have big consequences. According to government statistics, Japan's self-sufficiency in seafood in 2005 was just over 60%, for meat that was only a little over 40% - while most meat-eating countries were at least 80% self-sufficient in meat, and many had surpluses. Those figures probably influence the FSC's management of mercury intake much more than if policy were determined at a less central level.

Somewhere in those links was a comment on the fact that mercury levels in Japanese people have been falling for many years now. No doubt this is also seen as a reason not to rush to implement economically and politically sensitive restrictions.

Meanwhile, the issue of diet for pregnant and nursing women in Japan is clouded by the issue of fish as traditional diet, and the issue of maternal weight gain. Whatever the rights and wrongs of the maternal weight gain issue, Japan does have a high rate of low birth weights for babies, a rate which started to climb at the same time that women started receiving advice to limit weight gain very strictly during pregnancy.

The MHLW comment about not wanting to put pregnant women off their fish is probably linked to a real risk of pregnant Japanese women cutting their protein intake too far - especially if they perceive milk as loaded with dioxin, meat as "fatty" , eggs as possibly riddled with salmonella, and chicken as contaminated with hormones.

With the negative image of imported food here, the high prices of domestic meat and chicken, and the old-fashioned image of soy foods, young women's diets are at risk of being low in protein.

The reason I translated that great long list of species and recommended limits was because that kind of specific information is not easy to come by in English for women having children here.

I will try to add some information later on just which commonly available (in Japan) fish tend to have the lowest levels of mercury, but it looks as if I will have to comb through species lists myself to get that - I haven't found a handy compilation yet.

[Hiroyuki]

First of all, here is smallworld's post on hijiki.

Secondly, Fat Guy has already started a similar topic (now merged into another thread), in which I posted a link to this pdf file.

For those of you who can read Japanese, here is a good comprehensive list on how much of which fish a pregrant woman can eat per week, as well as which fish she is forbidden to eat.

[Dianabanana]

Does mercury have a taste?

I ask because although I have always loved sushi since I was a teenager, I've never been too crazy about tuna due what I perceive as a "metallic" taste. This can't be psychosomatic because I've been saying it since about 1984, when I don't think this mercury issue was well known, or at least not to me.

[helenjp]

A metallic taste could be something bad, but as far as I know, a metallic taste isn't very likely to occur from eating raw fish with high contents of methyl mercury (that is, organic mercury). That is, the fact that raw fish does or doesn't taste metallic probably isn't a very accurate guide to mercury content.

More likely, you have a good sense of smell and taste, and pick up the "iron" taste of blood in rare steak or tuna sashimi.

Alternatively, some iron salts used to prevent fish and meat from staling might leave a tang, but that seems an unlikely explanation if you notice this taste most times when you eat raw tuna.

[Dianabanana]

A metallic taste could be something bad, but as far as I know, a metallic taste isn't very likely to occur from eating raw fish with high contents of methyl mercury (that is, organic mercury). That is, the fact that raw fish does or doesn't taste metallic probably isn't a very accurate guide to mercury content.

More likely, you have a good sense of smell and taste, and pick up the "iron" taste of blood in rare steak or tuna sashimi.

Alternatively, some iron salts used to prevent fish and meat from staling might leave a tang, but that seems an unlikely explanation if you notice this taste most times when you eat raw tuna.

←

Yes, I notice it every time I have raw tuna. There's no denying that I have a distressingly good sense of smell and taste. I wish it weren't quite so keen. I wonder if it is the blood that I'm tasting. Good one, Helen!

[smallworld]

First of all, here is smallworld's post on hijiki.

Secondly, Fat Guy has already started a similar topic (now merged into another thread), in which I posted a link to this pdf file.

For those of you who can read Japanese, here is a good comprehensive list on how much of which fish a pregnant woman can eat per week, as well as which fish she is forbidden to eat.

←

Thanks for finding the hijiki thread, Hiroyuki. And although I was aware of the other mercury thread, I wanted to start a new one because I think it's a different issue.

In my opinion this is not just about the diets of pregnant women, and in any case the advice that expectant mothers receive is so different in each country that mercury levels are just the tip of the iceberg, and it would be necessary to go way off topic to really explore the issue. Rather, I am curious as to why people in general aren't more concerned here, as mercury poisoning can effect anyone.

Granted, an adult would need to eat a LOT of tuna or whale to see any signs of mercury poisoning, but it is still at least theoretically possible, especially given the extreme popularity of tuna here. But what about kids? Especially infants and young children are at risk of mercury poisoning, but I haven't heard of any warnings. In fact, consumption of high-risk seafood seems to be encouraged in some cases: I understand that whale has been re-introduced to school lunches in some whaling communities. I find that alarming, and was just wondering if anyone else did, too.

[smallworld]

I'm not sure if you're quoting

Yes, my whole post was pretty much either quoting or summarizing from the linked sources, sorry if I didn't show that clearly.

I wanted to do two things - show what issues are being discussed by Japanese consumers, and also show what kind of information is available to the averagely curious consumer.

I'd be interested to hear what other coastal and island East Asian and Southeast Asian countries are saying on this issue, because the impression I get is that there is quite an east:west divide regarding the safety of wild fish.

Thanks Helen. It really is good to know that some information is out there.

I'd be interested in learning about the situation in other countries in the region too. But in some places I can imagine that simply getting food on the table is a far bigger worry than potential mercury poisoning, so it might not be that fair a comparison.

On the one hand, most food-safety coverage in Japanese media appears to concentrate on individual companies; rarely does anybody take on on entire industries - the dioxin and endocrine disrupters fuss is probably all but forgotten by most people, and it's quite possible that mercury issues could go the same way.

This is so true, and I think the current gyoza scare is a very good example (although it's more a case of an "individual country"). Many of my students have vowed never to shop at Co op again and are completely avoiding anything marked "made in China". Somehow JT has escaped their wrath and nobody seems to be examining just why frozen prepared foods have become so prevalent, and why Japan is so dependant on imports. And in 6 months the issue will be completely forgotten (I mean, did you see the huge line up for Akafuku's reopening last week?).

On the other hand, it is true that a big swing away from fish in a country with little agrarian land would have big consequences. According to government statistics, Japan's self-sufficiency in seafood in 2005 was just over 60%, for meat that was only a little over 40% - while most meat-eating countries were at least 80% self-sufficient in meat, and many had surpluses. Those figures probably influence the FSC's management of mercury intake much more than if policy were determined at a less central level.

I think that a big swing away from fish is inevitable in Japan, considering the way the world's waters are being overfished. Mercury in seafood is just one more reason why people here need to start examining the so called "traditional" fish-based Japanese diet. Not that I am suggesting that people stop eating fish and/or start eating more meat. But claiming that fish is a traditional part of the Japanese diet doesn't tell the whole story and the way people consume fish now is completely different from the way it used to be, when fish was locally caught, in season, and served in more reasonable quantities. There is nothing traditional at all about the current tuna fixation, and I think it's perverse that in most supermarkets (at least in my area) tuna gets its own large section of the seafood area. No other fish is given that much space.

The reason I translated that great long list of species and recommended limits was because that kind of specific information is not easy to come by in English for women having children here.

I will try to add some information later on just which commonly available (in Japan) fish tend to have the lowest levels of mercury, but it looks as if I will have to comb through species lists myself to get that - I haven't found a handy compilation yet.

←

That is definitely information that needs to be made available in English. At the same time the recommendations aren't too different from those of other countries, and considering that a lot of the fish is imported anyway, a woman can probably safely follow recommendations from her own country or from the Monterry Bay Seafood Watch.

[JasonTrue]

I still find it fascinating that so much ocean fish is served in mountain ryokan... often in portions unlikely to be eaten by someone who lives right on the coast on a typical day.

My understanding is that the mountain diet, at least 50-100 years ago, was totally different than now. I suspect urban wealth has also increased the scale of consumption of ocean fish in areas closer to the water, too.

[Ohba]

I still find it fascinating that so much ocean fish is served in mountain ryokan... often in portions unlikely to be eaten by someone who lives right on the coast on a typical day.

My understanding is that the mountain diet, at least 50-100 years ago, was totally different than now. I suspect urban wealth has also increased the scale of consumption of ocean fish in areas closer to the water, too.

←

Why not though? What's the furthest point from the ocean in Japan? Most fish would have travelled much further to reach port in Japan from the point where it was hoovered out of the sea than it will to get from the coast to the top of a mountain. I find it far stranger that in my hometown in Britain, just 6 miles from the sea, and with the excellent quality of fish and seafood in British waters, buying fresh fish is a near impossibility - a situation that is replicated in many parts of the country.

Edited February 15, 2008 by Ohba (log)

[JasonTrue]

Sure, it seems to make sense in an age of refrigerated transport by truck and air but historically, transporting fresh seafood via land routes more than, say, 20-30 land miles was relatively uncommon. The refrigerated transport is what's changed Japanese dietary habits. Even the distance that boats travel to obtain seafood has changed.

I'm not going to go so far as to say it's a terrible thing, but it's certainly contributing to overfishing and increased seafood prices.

If, 80-100 years ago, you were living in central Nagano, you would have consumed primarily river and lake fish, rather than ocean seafood, along with small game like birds and rabbits. (apparently also horse and locusts on occasion, but I don't know how long ago this goes back).

Of course, refrigerated transport has made the area more densely populated, too. There wasn't historically an economy of scale for transporting highly perishable food. Even the variety of vegetables available in the early 20th century was much smaller than now.