Is eating fish safe? A lot safer than not eating fish!

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This is going to be a long article and I know not everyone will have time to read it. So I’m going to summarize the key points right up front because I think this information is so important:

Overview

  • Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish
  • If a fish contains higher levels of selenium than mercury, it is safe to eat
  • Most species of commonly eaten fish in the U.S. have more selenium than mercury
  • Fish are not significant sources of PCBs and dioxins when compared to meat, dairy or vegetables
  • The benefits of eating fish regularly far outweigh the potential risks, which are neglible
  • Pregnant mothers and young children should eat 2-3 servings of oily ocean fish each week

These days a lot of people are scared to eat fish. They’ve been told that fish are full of contaminants like mercury, PCBs and dioxins that cause neurological problems and may increase the risk of cancer. Pregnant women have been especially warned due to the supposed risk of these toxins to the developing fetus.

In the last few articles I’ve established the importance of the long-chain omega-3 fatty acids EPA and DHA in human health. I’ve argued that the conversion of plant-based omega-3 fats like ALA into the longer chain EPA and DHA is extremely poor in most people.

The conclusion is obvious: fish should be a part of our diet. But is it safe to eat fish?

You might be surprised to learn that the answer is a resounding yes. In this article I’ll demonstrate that concerns about toxins in fish have been overblown, and that there is almost no risk associated with eating fish when a few simple precautions are taken.

The selenium story

Although people are increasingly concerned about the effects of mercury levels in fish, recent evidence suggests that the trace amounts of mercury in the fish Americans eat aren’t high enough to pose a health risk.

But measuring only mercury significantly exaggerates this risk, because it ignores the important role of selenium.

Selenium is plentiful in many ocean fish species, but the public is unaware of its protective role against mercury. Selenium has high binding affinity for mercury. This means that when the two elements are found together, they connect, forming a new substance.

This new substance makes it hard for the body to absorb the mercury separately. Simply put, when selenium binds to mercury, mercury is not longer free to bind to anything else – like brain tissue.

Studies have shown that relevant amounts of selenium (Se) can prevent oxidative brain damage and other adverse effects associated with mercury toxicity. (PDF)

University of North Dakota researcher Nicholas Ralston has published several papers on the protective effects of selenium. He describes the relationship between selenium and mercury as follows:

Think of dietary selenium as if it were your income and dietary mercury as if it were a bill that you need to pay. Just as we all need a certain amount of money to cover living expenses such as food and rent, we all need a certain amount of selenium.

And guess what foods are highest in selenium? You’re right! 16 of the 25 best sources of dietary selenium are ocean fish.

He goes on:

Only one major study has shown negative effects from exposure to mercury from seafood, and that seafood was pilot whale meat. Pilot whale meat is unusual in that it contains more mercury than selenium. When you eat pilot whale meat it’s like getting a bill for $400 and a check for less than $100. If that happens too much, you go bankrupt. On the other hand, if you eat ocean fish, it’s like getting a check in the mail for $500 and getting a bill for $25. The more that happens, the happier you are.

What Ralston is telling us is that as long as the fish we’re eating has more selenium than mercury, there’s nothing to worry about.

Fortunately, studies by several independent organizations have consistently shown that most of the fish we eat contain significantly more selenium than mercury. Fish that contain more mercury than selenium include pilot whale, tarpon, marlin, swordfish and some shark.

The following chart illustrates the relative levels of selenium and mercury in commonly eaten ocean fish:

The selenium health benefit value (SeHBV)

Researchers have proposed a new measure of seafood safety called the Selenium Health Benefit Value (SeHBV) that takes the protective role of selenium into account.

Fish with a positive (above zero) SeHBV ratio would be safe to eat, whereas fish with a negative ratio would be unsafe. Using these criteria, most varieties of ocean fish have positive SeHBV ratios and are thus safe to eat.

A study conducted by the Energy & Environmental Research Center (EERC) and the Environmental Protection Agency (EPA) also found that an estimated 97% of the freshwater fish from lakes and rivers in the western U.S. are safe to eat. It is the only study I’m aware of that has measured both mercury and selenium levels in the tissues of freshwater fish. 1

So how much fish is safe to eat?

The joint recommendation for fish consumption of the EPA and FDA as of 2004 is as follows:

  • Eat up to 12 ounces (2 average meals) a week of a variety of commonly eaten fish and shellfish found consistently low in mercury, including shrimp, canned light tuna, salmon, pollock, and catfish
  • Limit albacore tuna to 6 oz. per week
  • Do not eat shark, swordfish, king mackerel, or tilefish because they contain high levels of mercury

Notice that these recommendations are already quite liberal compared to the fish-phobes who suggest we avoid fish entirely.

But even these recommendations are too strict, because they don’t take the protective effects of selenium into account. As long as the fish is higher in selenium than it is in mercury, there’s no reason to limit consumption to 12 ounces per week.

What about dioxins and PCBs?

PCBs are synthetic organochlorine compounds previously used in industrial and commercial processes. Dioxins are organochlorine by-products of waste incineration, paper bleaching, pesticide production, and production of certain plastics. Yummy!

While it makes perfect sense to try to avoid these toxins to the greatest extent possible, abstaining from fish isn’t a particularly good strategy.

The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals.

The primary concern with PCBs and dioxins is cancer. Animal studies and some evidence in humans suggest that both are carcinogenic.

However, an analysis has shown that, per 100,000 individuals, consumption of farmed vs. wild salmon would result in 24 vs. 8 excess cancer deaths, respectively, while consumption of either farmed or wild salmon would result in 7,125 fewer coronary heart disease (CHD) deaths.

Another analysis of the same data suggested that, for all ages evaluated (25-35 to 85 years), CHD benefits outweighed cancer risks by 100- to 370-fold for farmed salmon and by 300- to more than 1000-fold for wild salmon.

It’s important to note that the benefits of fish consumption are based on prospective studies and randomized trials in humans, whereas estimated cancer risks include a 10-fold safety factor and are based on experimental data in animals and limited studies in humans at extremely high doses.

Cancer estimates also assumed lifetime salmon consumption of 1,000 mg/d of EPA & DHA (four 6-oz servings of wild salmon every week for 70 years). Of course virtually nobody in the U.S. currently eats this much salmon.

On the other hand, CHD mortality reduction may be achieved with lower intake (i.e. 250 mg/d – one 6-oz. wild salmon serving per week). At this intake, CHD benefits would be the same (7,125 fewer deaths) while lifetime cancer risk would decrease by 75% (6 and 2 estimated deaths per 100,000 for farmed and wild salmon respectively). The CHD benefits would outweigh cancer risks by more than 3500-fold in the case of wild salmon.

Once again, with few exceptions (the species of fish with more mercury than selenium), it’s not only safe but incredibly beneficial to eat fish regularly.

How beneficial? Let’s find out.

Fish consumption, cardiovascular disease and total mortality

In 2006 Mozaffarian & Rimm published a paper in JAMA called “Fish Intake, Contaminants and Human Health: Evaluating the Risks and Benefits“. They analyzed several studies that examined the impact of fish consumption on both coronary and total mortality. They found that modest fish consumption (e.g. 1-2 servings/wk) – especially of oily fish higher in EPA and DHA – reduced the risk of coronary death by 36% and total mortality by 17%, and may favorably affect other clinical outcomes.

The authors summarized their findings this way:

For major health outcomes among adults, based on the strength of the evidence and the potential magnitudes of effect, the benefits of fish exceed the potential risks.

And:

For women of childbearing age, benefits of modest fish intake, excepting a few selected species, also outweigh risks.

They also pointed out that the Japanese eat 900 mg/d of EPA & DHA on average, and have death rates from coronary heart disease 87% lower than those in Western populations (like the U.S.).

If you’re interested in learning more about this study, I recommend listening to the JAMA Audio in the Room interview with its lead author, Mozaffarian.

Fish consumption, pregnant mothers, and children

DHA is essential for proper development of the brain. It is preferentially incorporated into the rapidly developing brain during gestation and the first two years of infancy, concentrating in the gray matter and retinal membranes.

In a meta-analysis of 14 trials, DHA supplementation improved visual acuity in a dose dependent manner. In another trial of 341 pregnant women, treatment with cod liver oil from week 18 until 3 months postpartum raised mental processing scores at age 4 years.

This is consistent with observational studies showing positive associations between maternal DHA levels or fish intake during pregnancy and behavioral attention scores, visual recognition, memory, and language comprehension in infancy.

An FDA report issued in 2008 noted that the nutrients in fish – especially n-3 LCFAs, selenium, and vitamin D – could boost a child’s IQ by an estimated ten points. 2

The FDA report summarizes evidence suggesting that the greatest benefits to children would result if pregnant women of childbearing age, nursing mothers and young children ate more than the 12 ounces of fish per week currently recommended by the EPA.

According to the National Fisheries Institute, Americans currently consume only five ounces a week of fish high in n-3 LCFA, which is less than half the recommended amount. The NFI also estimates that up to 14 percent of women of childbearing age eat no fish at all, despite the fact that n-3 LCFA are essential to proper fetal brain and eye development.

Based on the new understanding of selenium’s protective role, and the importance of DHA for fetal and early childhood development, pregnant mothers should be advised to eat oily ocean fish regularly.

Fish consumption and autoimmune and inflammatory disease

The first evidence of the significant role of dietary intake of n-3 LCFA in reducing inflammation came from epidemiological observations of the low incidence of autoimmune and inflammatory disorders in a population of Greenland Eskimos compared with gender- and age-matched groups living in Denmark. The Eskimos in this study had dramatically lower rates of psoriasis, asthma and type 1 diabetes, as well as a complete absence of multiple sclerosis.

Animal and human studies suggest that n-3 LCFA suppresses cell mediated immune responses. Increasing the amount of n-3 LCFA while decreasing omega-6 fatty acids leads to improvements and a decrease of steroid use in patients with rheumatoid arthritis and asthma.

This is because omega-3s have been shown to suppress the capacity of monocytes to synthesize interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 and TNF are the principal mediators of mediation in several different inflammatory and autoimmune conditions.

Summary

This is simply a re-cap of the overview presented at the beginning of the article. But it’s worth repeating.

  • Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish
  • If a fish contains higher levels of selenium than mercury, it is safe to eat
  • Most species of commonly eaten fish in the U.S. have more selenium than mercury
  • Fish are not significant sources of PCBs and dioxins when compared to meat, dairy or vegetables
  • The benefits of eating fish regularly far outweigh the potential risks, which are neglible
  • Pregnant mothers and young children should eat 2-3 servings of oily ocean fish each week
  1. Energy & Environmental Research Center, University of North Dakota (EERC). EERC Research Finds Mercury Levels in Freshwater and Ocean Fish Not as Harmful as Previously Thought. June 22, 2009. Accessed at http://www.undeerc.org/news/newsitem.aspx?id=343
  2. Energy & Environmental Research Center, University of North Dakota (EERC). EERC Research Finds Mercury Levels in Freshwater and Ocean Fish Not as Harmful as Previously Thought. June 22, 2009. Accessed at http://www.undeerc.org/news/newsitem.aspx?id=343

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Comments Join the Conversation

    • Susan says

      I found your article very informative. You make the statement: “Most species of commonly eaten fish in the U.S. have more selenium than mercury”.
      The question I have is, what about fish from Vietnam, China, etc? Finding fish that originates in the US is almost impossible!! I know that the US fish guidelines and specifications are much more in depth and that from other countries, but can they be safe to eat?
      Thanks.

  1. says

    Wow, great article. When I was researching what my ancestors ate,  the Welsh. Not only were they introduced to grains much later than everyone else, oats about 1,000 years ago, they also ate lots of salmon. It could be readily caught in the rivers and was considered poor peoples food, and some were known to eat salmon up to 4 times a week. A far cry from the modern diet, very radically different indeed.

    I always learn so much here, and it helps alot of pieces of the puzzle come together.  Thanks!

  2. alumiere says

    Great piece, there has been lots of information I didn’t fully comprehend in this series. But I have a follow up question: Do you have suggestions for people who are allergic to seafood? As a child I could eat seafood no problem, and miss it.
    However, I got mercury poisoning in chem lab in college, had chelation therapy, and ever since anything that comes from the ocean or lake makes me at best violently ill and at worst sends me to the hospital after a day or two of being unable to keep even water down.  Fish oil that’s been detoxed? Nope. Farmed fish that’s supposed to be mercury free? Nope. A bit of seaweed or fish stock used in food prep? Nope.  Frog legs (we used to catch them and cook them once or twice a week on summer vacation)? MSM/Chondrointin/Glucosamine supplements? Octopus or squid? No, no, no…
    I know I’m not getting proper ratios of Omega 3′s, but I have no idea how to fix this. Also, I really miss blackened salmon, tuna salad, sushi, crabcakes, you name it.  Any suggestions? (I should add I have auto-immune adrenal/thyroid disease, in treatment including added selenium, so that’s not the answer).

  3. Chris Kresser says

    I’ve never heard of anything like that, so I don’t really have any ideas.

    The best thing you could probably do is strictly limit omega-6 intake and take relatively high doses of flax oil and evening primrose oil.  The lower your omega-6 intake, the higher your conversion rates of ALA to EPA & DHA will be.

    I was going to suggest vegetarian DHA, but it’s made from marine algae so I doubt you’d be able to tolerate it.

  4. Matthew says

    Once again, very informative. This whole selenium, mercury thing is very good to know. Have you heard anything about selenium/mercury levels in other kinds of seafood like shrimp, crab, octopus, etc… ? Also DHA and EPA levels? I’m living in Taiwan right now which has a huge seafood component to its diet so its cool to hear reassuring info about fish consumption. There’s also loads of other kinds of seafood so just curious if you knew anything about their safety.  I can’t imagine it being that harmful though when so many people eat it and have been doing so for quite awhile.  I guess the issue is with recently introduced harmful substances entering the food web but it still seems the benefits would outweigh any costs.
     

  5. Chris Kresser says

    Matthew,

    I know that shrimp and crab both contain selenium, but I don’t know the relative levels of mercury and haven’t seen studies comparing mercury and selenium. However, Ralston didn’t include them on his “don’t eat” list, so I’m assuming they are safe.  If you want to be sure, just increase your intake of other selenium rich fish and foods.

    There is an environmental consideration with shrimp harvesting, but that varies from area to area.  I don’t know the situation in Taiwan.

    • says

      Hi Matthew and Chris,

      I’m also living in Asia, Mainland China, at the moment and I’m a bit worried of buying seafood from the local markets because of the effects of farming around here ie. chemicals, anti biotic use, pollution, etc.

      If you gather any useful information on seafood safety in Taiwan/China I would love to hear it.

      Thanks

  6. Molly says

    Thank for such an informative article on the positives of eating Fish. Also it’s nice to read that, ” The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals.” Fish is favorite of mine and with the media attacking salmon, and even more farmed salmon, it was nice to read some more positive articles about my favorite food!
    Both Health Canada and The FDA have given farmed salmon the Green light. The demand for wild salmon is higher than the supply. With over fishing in our waters we need to take the pressure off wild salmon and turn more to farmed salmon.
    Thank you for this useful information
    Kind Regards,
    Molly W.
     

  7. Ginger says

    An interesting article that addresses a real problem with some people. All the talk of eating fish being dangerous was putting me off, so thanks. It might be beyond the scope of this blog, as its a health blog, but would you consider talking about the sustainability of eating fish? That’s something that really worries me.

    • Chris Kresser says

      I mentioned in this article that sustainability is a real concern, and that choosing fish that are certified as safe by the Marine Stewardship Council is probably the best bet. I also recommended a book in the article if you want to learn more.

  8. SV says

    Chris,
    The idea that “Selenium protects against mercury toxicity, and 16 of the 25 highest dietary sources of selenium are ocean fish” sounds too good to be true!  After hearing many people recount stories of having their mercury levels tested, and coming away horrified with the results, I’ve drastically cut back on my fish intake…  which sounds like it might have been a mistake.  One point of clarification:  would one’s mercury level appear to be the same, regardless of whether or not the mercury had been detoxified by selenium?  Or does selenium physically change the nature of mercury, thereby lowering the amount shown in a test result?  I only ask because it was my impression that heavy metals, like mercury, take an extremely long time to dissipate once ingested.

  9. Chris Kresser says

    When mercury binds to selenium a new compound is formed, so I believe it wouldn’t show up on the tests.  However, mercury testing is a controversial area.  Some practitioners have pointed out that all of us have some level of mercury in our systems. The question is how much harm it’s causing, and whether it’s responsible for whatever symptoms you’re experiencing.

    • Lisa Eastley says

      Do you know of any information on the cooking of fish and its effects on the EPA/DHA content?

      • gh says

        I’d like to know this also. I have not found most fish oil supplements to be effective, due to rancidity or being denatured. I’ve never noticed benefit from eating fish, but have from a couple of the fish oil supplements I’ve taken. Wouldn’t cooking turn the fish oil rancid?

    • brett says

      Hey Chris can you point me in the direction of those studies showing selenium complexing mercury? I can’t find any with such conclusive correlational findings.

  10. SV says

    I see.  Do you know of anyone who has endeavored to at least do some personal testing, in regards to fish consumption and mercury levels?  I really want to believe the selenium argument, but (in the spirit of this blog!), I am a bit skeptical.  The chart you highlighted from the Western Pacific Regional Fishery Management Council didn’t do much to quell my suspicions.  The last line of the paper (which was, incidentally, partially funded by the US Tuna Foundation and the Fisheries Scholarship Fund) is certainly true: “Consideration of mercury-selenium relationships in diet and tissues of exposed individuals will clarify risk:benefit relationships associated with fish consumption.”  Maybe that will be the Ralston’s next project (by the way, it’s remarkable that there seem to be no fewer than *three* Ralstons studying this topic…?  Two of the four authors of the paper, plus the other one you quoted in your post!).

  11. says

    Chris,
    I posted a short blog praising this article and your site on one of my blogs (http://dropoutnation.blogspot.com/2010/06/good-news-for-good-health.html) a couple of weeks ago.
    Today I discovered a comment by someone from Got Mercury leading me to a site with a mercury content calculator that seems to disagree with your findings.
    http://seaturtles.org/article.php?list=type&type=75
    I’m not altogether sure how to address this. I find your site highly informative and your research would seem to be impeccable while the studies they site are a bit less convincing.
    Any feedback from you would be appreciated since it is my intention to promote your site whenever possible.
    Thanks, Richard
    There is no way to Peace. Peace is the Way.

    • Chris Kresser says

      Richard,

      There’s nothing there that I haven’t already addressed, as far as I can tell. As I’ve shown in my articles, you have to consider the protective value of selenium. If the amount of selenium in a fish is higher than its mercury content, then there’s no safety issue. Fortunately, that’s true for most commonly eaten species of fish.

  12. William says

    Chris, I’ve got a question that’s eating at me.  I love sushi, and it would be great for me to believe it’s safer than I’d thought.  Your writing explanation about selenium being protective against mercury seems reasonable to a non-chemist like me, but I recently watched The Cove and it suggested that the high mercury in dolphin meat was having a horrendous impact on the people who ate the dolphins.  If the dolphins are eating (presumably) mostly fish that have more selenium than mercury, then why do they have such a high mercury content (to the point of making people sick)?  Is this a bogus claim in the movie or is it evidence that selenium doesn’t do as much good as you’re suspecting?

    • Chris Kresser says

      Perhaps because they concentrate the mercury. Pilot whale is another type of seafood consumed in some parts of the world that is higher in mercury than selenium – and I imagine it also eats mostly fish that are higher in selenium. I’ve not seen dolphin on that list, but that may be because dolphin is not commonly eaten in most parts of the world.

  13. William says

    Thanks for the response.  My recollection from the movie is that the mercury levels were sky high.  I should have looked into it a bit further before posting here… wiki has an entry on the film and it seems that the mercury levels were overstated.  Though I’d still never eat dolphin.  :)  Keep up the good work.

  14. Jen says

    Hi your site is greatly informative. I have listened to the podcast of Stephen Guyenet as well. But, I have to tell you I have been reading over Dr. Joel Fuhrmans’ site about to “eat fish or not”, it was enough to scare the daylights out of folks. Here it is…
    http://www.drfuhrman.com/faq/question.aspx?sid=16&qindex=6

    I always thought the good in fish outweighed the bad, especially after your articles. But now am wondering?? Hmm??? Or maybe Dr. F is not as informed….

  15. Sifter says

    •Fish are not significant sources of PCBs and dioxins when compared to meat, dairy or vegetables
    •The benefits of eating fish regularly far outweigh the potential risks, which are neglible

    I like your blog and have learned a lot. But I’m having trouble with the two bullet points above. I”ve googled a March 2010 report stating that some fish oil brands, like TwinLab and Nature Made, have very high levels of PCBs, which apparently have no standards as to what consititute ‘safe’ levels! There was also a report two years ago from Michigan, I think, showing that high doses of fish oil caused late stage colon cancer in mice. The tumors took a mere 4 weeks to present themselves! Apparently, the anti inflammation properties of fish oil are so good that they also curtail the defenses against various intestinal bacteria, necessary to kill off cancer cells.

    I appreciate your fairness and tireless research, but I just don’t see where you have addressed these worrisome issues. Please advise and thank you in advance.

  16. Joe E says

    There isn’t any information on freshwater fish in this article, does this exist for selenium levels? I eat lots of freshwater fish, being from the upper midwest as well as an avid fisherman, and have always doubted the mercury scare tactics. Any information on this would be terrific!

  17. Chris Kresser says

    Joe: good news for you.

    “Results from the first study, conducted jointly by the EERC, the U.S. Environmental Protection Agency (EPA) Western Ecology Division, and the University of Missouri’s Nuclear Reactor Center, show that an estimated 97% of the freshwater fish from lakes and rivers in the western United States are safe to eat. Conducted in 12 states in the western United States, it is the only study of this magnitude that has measured both mercury and selenium in fish tissue.”

    See full article here: http://newsletter.vitalchoice.com/e_article001496263.cfm?x=bfPRTnr,b7b1jv7h,w

  18. says

    Hi Chris,
    I have a question after reading this. When the selenium binds with the mercury does this cause the selenium to be unavailable for use by our bodies? Does the protective action of this process cause the selenium to be excreted with the mercury?
    Thanks for your work.
    Hannah

  19. jackie says

    what about the broadway actor who had really bad mercury poisoning from eating lots of sushi? i think his name is jeremy piven……..

  20. John says

    I thought PCBs were mainly a problem in farmed fish, which you did not cover, because of what they are fed. Same with cattle and chicken. They are fed industrial food waste (ground up carcasses, feathers and worse) and other bizarre but cheap ingredients. Isn’t it important, for your recommendations to be valid, to warn consumers to make sure they know the fish they eat is wild caught?

  21. says

    Thanks, Chris. Very informative. I reposted this on my FB page and a reader asked, “What about the concerns of radiation from Japan on the world’s oceans?” I personally don’t think this is an issue, for non-Japanese fish, but what do you think?

  22. Andriana Lam says

    This is very interesting- a few years ago I was tested for mercury and had high levels of mercury- I did chelation to get rid of it – the thing is I didn’t know if the cause was my mercury fillings (which I subsequently had removed) or the fact that during a summer college course for 8 weeks I had a tuna fish sandwich from the college cafeteria literally almost everyday those 8 weeks- which one do you think it could have been? My mercury levels were quite high. It seemed like you were saying to still be cautious with tuna- is that because it’s ratio of selenium to mercury is not as good as some other fish like salmon?

    Thanks!

  23. Fred Perez says

    Hello Chris

    This is a great and informative article. I’m glad to hear this because whenever I eat fish it has a dramatic effect on my overall health, including a very noticeable, at any weight, leaned out face. I tend to put weight on chin and cheeks, and fish brings this down within 2-3 days of eating it. Any ideas on why this is?

    Also, with the recent happenings in Japan, should we be taking any precautions regarding what type of fish to buy or not?

  24. Candace says

    Your article makes me feel much better about eating fish. My concern which I don’t think has been addressed here (I scanned the comments so I might have missed it) is what’s done to the fish after it’s caught. I keep reading about chemicals grocery store fish departments put on the fish to make it look better on display. I always ask grocery managers about this, but who is going to admit, “yeah, we poison our fish so it looks pretty!” Sometimes I buy fish and I feel really sick after eating it so I’m always leery about what I don’t know and the marketing scams businesses use to make an extra buck. It’s easier to just not eat it rather than worry.

    • says

      When it comes to grocery stores bleaching and using borax to clean and polish junk fish, the Thailand fish farms seem to be the worst offenders. (Source: BottomFedeer by Grescoe )

      • Jonathan says

        Is Borax even an issue though? http://en.wikipedia.org/wiki/Borax Its a good source of Boron which is a trace mineral we need. The other things they used to bleach, clean, and polish the junk fish might be bad, but I’m thinking a little Borax residue isn’t an issue. Your thoughts?

  25. Mike Ellwood says

    What is king mackerel?

    Is ordinary mackerel ok? What about herring & sardines/pilchards?

    What about the fish in general available to those of us in the UK? (North Atlantic and North Sea I suppose).

    For ALAs, I notice you recommend flax seed oil. In an interview with Dr Mercola, Dr Rudi Moerck was as skeptical about flax seed oil as you are about fish oil (he is also cautious about fish oil). The reason being that it is oxidised even by the time it gets into the bottles/capsules.

    For ALAs, his preference would be chia seeds, which he says are smaller and digestible without being ground (whereas flax seed are indigestible, and once ground, need to be consumed within a few hours, so buying ready ground seeds is not an answer).

    For DHA/EPA he strongly recommends krill oil, but then, you could say he is biased in that respect.
    I have read that you are as lukewarm towards krill oil as you are towards fish oils, so I assume you will not agree with him on that. However, I would be interested to hear your take on his comments about flax seeds, flax seed oil, and chia seeds.

    • says

      Flax seed oil, from the information that I’ve seen, does not convert well into our body. As far as sardines go, they have very high selenium, iodine, and omega 3 levels and very low mercury levels. The smaller the fish, in general, the lower the mercury level. According to Seafood Watch, look for Mackeral from the Atlantic and areas other than the Gulf of Mexico, where overfishing is occuring.
      When it comes to Dr.Mercola, btw, he seems like a fear mongerer more than a reliable source.

      • Jonathan says

        Since you seem to be a critic of Dr. Mercola I’m curious as to your thoughts on one particular product that I’m thinking of buying.

        I’ve heard of Full Spectrum lights being good from other sources so I think they make sense, but I’m wondering if his specific bulbs are a good pick? Its 119 dollars for 12 bulbs which is about 9 something a bulb. Do you know of any good sources for a close to natural light full spectrum bulb that’s cheaper?

  26. Harri says

    Thank you for this analysis, glad to see some sanity backed with data to counter the fearmongering.

    Now, if I could only source BPA-free canned tuna in Europe…

  27. Iris says

    This is a very informative article, thank you! I would like to ask one question concerning PCBs in other foods (esepcially meat). I only buy organic meat which is not possible for fish (organic fish often is farmed fish, I think “oragnic wild-caught” is just nor possible). Does organic meat contain significant levels of PCBs as well, esepcially when compared to wild caught fish? I have found the information that PCBs gather in the fatty tissue, are there significant amounts in lean seafood?
    Thank you!

  28. Ben says

    Chris,

    I’m from Minnesota and there is plenty of freshwater fish to be caught and consumed. I’ve been searching the internet for more info on the selenium levels of the fish in the Twin Cities metro area (mainly northern pike, largemouth bass, crappies, sunfish and walleye), but the info available is vague at best. Dr. Rolston’s research seems to indicate that most minnesota fish should be high in selenium, but I would imagine it would be different in the Metro than in the rest of Minnesota, due to more industry, greater population density, less open land and little to no farming. What are some markers I can look for, such as selenium levels in soil, other animals, etc that would indicate whether the fish from metro lakes have high selenium levels. Thanks for any response.

    Ben

  29. Nismo says

    I’m struggling to find a site detailing the selenium v mercury content in fish. Do you have any suggestions or links to this information?

  30. Brendan D says

    Its post like this that make people very ill…mercury at ANY level is horribly toxic to the body. I’ve never had filling in my mouth but became very mercury toxic just from eating tuna. I would highly recommend anyone who reads this to do your own research on the subject. No matter how protective selenium is mercury does not leave the body…it stays in your body (and more specifically your brain) for a very very long time, in which it causes a host of different problems. Pretty much any mainstream “disease” in my opinion is caused from some level of heavy metal poisoning (usually mercury poisoning).

    Always do your own research folks.

  31. Rob Ehite says

    Hi Chris,

    great article. I am recently a converted pescetarian (with ample amount of raw eggs, fruits, veggies, and unpasteurised cheese thrown in for good measure). I eat a lot (as in every day) of Chilean farmed mussels, shrimp, and Alaskan pollock, and one of the criteria for me choosing these foods was, apart from them being among the cheap seafood in the UK (my budget is very tight), the low environmental impact, low level of mercury, PCB’s and dioxins.

    However, i was reading Denise Minger’s comments about The China Study, and when she reviewed the parts concerning seafood intake and disease, she said that regular seafood consumers need to be wary of CADMIUM intake. Looking into it, cadmium seems to cause even worse problems than mercury. But surprisingly, everyone seems to focus on mercury when they are concerned about metals from fish.

    Thanks to Darrin, one of the commenter’s on the PHD blog, I managed to find some limited info on cadmium intake in the type of seafood i eat mostly – i.e crustaceans and molluscs http://www.foodstandards.gov.au/consumerinformation/nuttab2010/nuttab2010onlinesearchabledatabase/onlineversion.cfm?&action=nutrientFoods&category=Minerals&nutrientID=CD .

    Many studies examining cadmium concerns on seafood conclude withthe comment along the lines of “because high cadmium seafood is not a major part of the diet, you should be ok” or “as long as you dont eat it (e.g. mussels) every day, you should be ok”. The problem is, it is a major part of my diet and i DO eat it every day!

    Am i right to be concerned over cadmium levels if i eat a daily diet containing molluscs and shrimp daily?

    • Jonathan says

      Iodine protects from Radiation to some extent…whether its enough to protect from that much…I’m not sure. It might be good to avoid fish from that immediate area or to have plenty of non radiated fish from other areas.

      You might do some searches on it as there might be more on Iodine and its protective capacity in regards to radiation. I read something about it on Jack Kruse’s website but don’t remember which blog post.

  32. says

    Great article. I would like people to keep overfishing in mind, and please look up the fish you buy through Seafood Watch before purchasing. I think as proponents of paleo, we should also be proponents of environmental safety through our actions. Saying that, I’m about to go eat some oyster and sardines.

  33. Ray says

    I really appreciate this article… I just started eating fish again recently after a few years of abstinence, and its been doing MuchGoodness for me. The facts presented here certainly open my mind to how much options there are available… I was being rather restrictive about it, which in a way is a good thing. Now I can expand my palette in confidence!

  34. says

    I understand that fish, cold water, fatty, ocean fish is good for us. But what about all those hunter-gatherer people–which we all were before agriculture–that didn’t live near the ocean, didn’t eat much if any fish, yet were quite healthy. The Masai comes to mind, as well as the North American Plains Indians, and the Koi San of South Africa.

    • Jonathan says

      Did the North American Plains Indians not eat freshwater fish? They do have many of the benefits of ocean fish though not to as much extent. Also I’ve heard insects provide some of the same benefits as fish…could that be something they eat?

  35. SteviB says

    Chris, is shellfish included in this information? When you recommend 2-3 servings of oily ocean fish per week for pregnant mothers and children, am I assuming you’re not including low mercury shellfish like shrimp, bay scallops and oysters in this? Thanks in advance!

  36. says

    Chris – Do you think that pregnant/trying-to-conceive/breastfeeing women need to worry about mercury or do you think that the rest of this article also applies to these women? You recommend oily fish, but what about the others? Thanks in advance and I love reading your work.

  37. says

    Chris, Interesting, informative article but you don’t mention anything about purines. Sardines have very high purine levels up to 1,000 mg per 3.5 ounce serving. You mention “there’s no reason to limit (fish) consumption to 12 ounces per week”, but what about the problems with purines mentioned here in studies like this:

    Choi, H. K., K. Atkinson, E. W. Karlson, W. Willett, and G. Curhan. “Purine-Rich Foods, Dairy and Protein Intake, and the Risk of Gout in Men.” N Engl J Med. 2004 350(11): 1093-103.

    Choi, H. K., S. Liu, and G. Curhan. “Intake of Purine-Rich Foods, Protein, and Dairy Products and Relationship to Serum Levels of Uric Acid: the Third National Health and Nutrition Examination Survey.” Arthritis Rheum. (2005). 52(1): 283-9.

    Thanks,
    Jay

  38. Andrea says

    what if your allergic to fish? I recently had a lab done with an said I was deficient in EFA. I take Noridic Naturals EFA’s, and I’m still deficient. Is this because I need to eat fish too? The issue is I’m allergic to shell fish.

    • Chris Kresser says

      If you’re only allergic to shellfish, you could eat salmon, mackerel, herring and sardines to get your EPA/DHA. Another option if you’re allergic to all fish is taking marine algae (which is where the fish get their DHA).

  39. Brian says

    Chris sorry if this has been covered before but I’m new to your site and haven’t had a chance to fully dive into all your great material.

    My dad doesn’t eat fish anymore. Basically he believes you will get sick if you eat anything from the Gulf because of the oil spill and anything from the Pacific because of the Nuclear Plant problems in Japan and all the “radiation soaked garbage” from the earthquake making its way to the west coast waters. Also radiation in the air coming over.

    To me I have trouble subscribing to this. I think if it were actually a problem we’d know not to eat fish….but alas, I don’t eat fish either. In my mind things are probably fine, but I like to get my information from sources I trust so I can better make a decision.

    Do you have any opinion on this? Are there websites/people you can point me to that would be able to give me something to tell my dad and restore his faith in fish (something he ate often his whole life)?

    Or is what he hears right? Should we be sticking to the Atlantic Ocean and fresh water fish?

    Thanks,

    Brian

    • Christina says

      I have the exact same fears. I wish I could get some information that pacific fish is safe to eat for young children.

  40. J says

    Great article! However why does know one seem concerned about the contamination that’s STILL going into the ocean from Fukushima and its effects on seafood????

    It’s not like the fish just stay near Japan. Obviously they swim throughout the pacific. I’d really love your thought on that Chris.

  41. Peter says

    Check out this article from SuppVersity before consuming any more fish:

    http://tinyurl.com/8jswlzb

    Additionally, the tests showing radioactive isotopes in fish — and the sparse (or lack) of safety testing — makes fish consumption a very risky proposition.

  42. Gregory Pais says

    Hi Chris,

    I’ve followed with interest your articles concerning eating fish and the issue of Mercury toxicity.

    Have you read this study in the Journal of Biomedicine and Biotechnology Volume 2012 (2012), Article ID 681016?

    A French research team sought to determine whether mercury from fish is less harmful than other dietary mercury, and whether beneficial nutriments from fish might counterbalance the deleterious effects of fish-associated mercury.

    Mice were fed one of three diets:

    Fish-based methylmercury diet: A diet that included fishmeal produced from fish containing five micrograms of methylmercury contamination per gram.

    Added methylmercury diet: A special diet higher in DHA and EPA, with added methylmercury chloride (considered more toxic than fish-associated methylmercury) also totaling five mcg/g.

    Control diet without mercury
    Apart from mercury and selenium content, the three diets were comparable. Only the fish group suffered significant behavioral abnormalities at the end of 58 days.

    The authors concluded:

    “The two mercury-containing diets are differing by the fact that mercury was brought by the addition of either pure methylmercury chloride or by mercurial species associated to fish. Therefore, any differential effects observed between MeHg-containing and fish-containing diets should be attributed to different chemical species of mercury present in one diet and absent from the other and vice-versa along with the possible intervening role of fish PUFA and selenium.

    If the beneficial role of fish nutrients such as PUFA and selenium was to counteract MeHg effects, the pattern of effects displayed after exposure to the fish-containing diet should appear less severe than that observed with the MeHg-containing diet. But in the present study, the mice fed the fish-containing diet displayed worse behavioral performances than those fed the control and the MeHg-containing diets, although the brain structures of both mercury-contaminated groups of mice contained comparable levels of mercury and even less in the striatum of those fed the fish diet.

    Therefore, the different chemical species of mercury within fish flesh are likely to explain the deficit in cognitive performance in the Y maze and the decreased locomotory activity in the open-field maze.”

    I’m not a big fan of extrapolating from mice to humans but I’d like to hear what you think of these results.

    Peace,
    Gregory

  43. says

    The Article is very informative.
    In Homoeopathy, Selenium is one of the great medicine, which is used for Prostetorrhoea, Constipation, Loss of weight, — . About 2000 symptoms covers Selenium. This article is very good to about Selenium and its sources as well as different views of readers.
    Many Thanks esp. to Chris Kresser and all commentators.

  44. Alana says

    I stopped eating fish as soon as the Fukushima disaster occurred, and I was eating it every day prior and experiencing dramatic health benefits. Why avoid the topic? I’ve noticed other practitioners with popular websites ignoring it also. I think we all see the elephant standing in the room. Why not address it?

  45. Stacy says

    How much fish is ok to eat a day and week?

    Which fish are ok and is tongal or yellow jack tuna ok, which are said to be low mercury tuna (can these be eaten once a day??

  46. Sylvia says

    Hi there nice article and very helpful, I’ve been reading to many articles who not saying the same thing and it’s getting confusing. I don’t know to much about fish since I’ve never eaten to much of it before, but been a vegetarian for almost a year I’ve decided to change to a pescetarian because i had to take some vitamins supplement and Omega 3 supp also. I went to a fishmarket because i like to buy fresh and since I didn’t know to much about fish the only thing I eat is salmon, shrimps, crab, lobster and talipia or sole. Since she didn’t carry any talipia or sole she recommended the ORANGE ROUGHY and I’ve notice in the research that I made when i got home that it was a species who were very HIGH in MERCURY, so now I’m not sure if I should eat it or not. I guess she didn’t know the species about it’s high mercury content, that she only knew that it was a species from New Zealand and Australia. I will really appreciate if you can help me about the Orange Roughy fish that I just bought if it’s okay to eat or it’s risky. I will never buy this kind again but i don’t want to trow it away. Thanks.

  47. tylor fitzgibbon says

    Hi Chris,

    Could you comment on the difference between wild and wild-caught fish. I would like to know if you have any information on the differences in nutrients and toxins.

  48. tylor fitzgibbon says

    Hi Chris,

    Great post!

    Two questions:

    1 Looking at it from the respective levels of nutrients and toxins is there a meaningful difference between wild and wild-caught fish?

    2 What are your thoughts on BPA-free canned fish or glass-jarred fish as opposed to fresh fish?
    I live in Taiwan and we have a great selection of local seafood, but I am suspcious of the amount of pollution in the surrounding waters and the fish here are generally sub-tropical and so not very fatty. I was thinking about purchasing some Wild Planet sardines and some various Crown Prince seafood products to compliment the local seafood I eat.

  49. Craig says

    Whew! What a relief to learn about the selenium connection. For what it is worth: I have been eating tuna sandwiches practically every day for over 50 years. I never grow tired of the taste and texture of a tuna sandwhich. I have also been consuming mostly wild salmon and tilapia for dinner a couple of times a week. That’s alot of fish consumption! I am a healthy 61 year old man. My mental faculties are completely normal. If one believed the scare tactics regarding fish/mercury consumption I would have been committed to a mental facility long ago with the amount of fish I have consumed over the decades.

    • BeeBee says

      Craig, it really depends on ur methylation status. Looks like u are able to detox metals properly, whereas other people might not be as lucky. It also depends on genetics/snps. But, i agree that this tends to be overblown. How do these levels in fish compare to other foods? How does the arsenic in rice compare to other foods? And, most importantly, how absorbable are these toxins?

      It also depends on what the rest of ur diet is like too

  50. Daniel says

    Dear CHRIS KRESSER

    Sorry, but I read the original article about PCBs and Dioxins in the american diet that you quoted in your article (INTAKE OF DIOXINS AND RELATED COMPOUNDS FROM FOOD IN THE U.S. POPULATION), and there’s something that needs urgent correction. You quoted that “The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals.” The information is not wrong, but is incomplete and could be misunderstood by the readers.
    The question is “why fish contributes only with 9% of ingestion of PCBs in the american diet?”. And the autors of the study gave the answer: “The share of TEQ contributed by fish is smaller than previous estimates, because fish is consumed in smaller quantities in the United States than in many other countries.” / Obs: TEQ = dioxin toxic equivalent
    So, IS NOT BECAUSE THE FISH IS A SAFE SOURCE!!!! By the way, the same study puts freshwater fish as the HIGHEST source of PCBs (1.7 TEQ ppt), and even the seafish is higher than chicken, and as bad as beef and pork (0.39 TEQ ppt) !!!!!!

    “Freshwater fish were found to have the highest wet weight dioxin toxicity, with 1.7 ppt TEQ, followed by butter with 1.1 ppt. Ocean fish, meat, poultry, sandwich meats, eggs, cheese, and milk desserts, as well as human milk, were found to have wet weight dioxin TEQ contamination in the range of 0.33 to 0.51 ppt.”

    And as the study shows, the safer food group are the vegetables, with only 0.01 TEQ ppt (ND=0) and 0.09 TEQ ppt (ND=1/2):

    “The food category with highest World Health Organization (WHO) dioxin toxic equivalent (TEQ) concentration was farm-grown freshwater fish fillet with 1.7 pg/g, or parts per trillion (ppt), wet, or whole, weight. The category with the lowest TEQ level was a simulated vegan diet, with 0.09 ppt.”

    By the way, when the same study shows that vegetables contribute with 22% of the PCBs/Dioxin intake is just because this group (fruits, grains, leaves, tubers, roots, etc) is the major part of our meal. Thus, in a vegan diet vegetables will contribute with 100% of the PCBs/Dioxin intake because vegans only eat vegetables. So is clear to see that this number percentage alone means nothing.

    Well, you don’t need to trust me, just read the original article by yourself: http://www.ejnet.org/dioxin/dioxininfood.pdf)

    Bottom line: fish is healthy when you think about omega 3, but YES, It is a very important source of PCBs and Dioxins.
    Best regards,
    Daniel

      • Daniel says

        Well, not me. Who are saying that vegetables have less PCBs and dioxins than the other food groups are the autors of the same article that was quoted by Cris. But this make sense, since the vegetables are at the bottom of the food chain.
        But in my opinion, being a vegan is not enough to garantee a healthy diet. You could be a vegan and just eat french fries all day long and drink soft drinks. Well, definitly that is not healthy.
        So we need to choose well what to eat (e.g., organic food, Brassica vegetables, nuts, all kinds of berries), and use the heathiest ways to mix and prepare the food. And we should not forget about daily exercises and, if you are a vegan, the B12 vitamin supplement.
        By the way, I’m not a vegan because once in a while I eat cheese (organic if available) and fish (the less contaminated varieties), but is rare. In the other hand, I never eat red meat or junk food and never drink soda.
        Best regards!
        Daniel

        • bee says

          Thanks daniel… u seem to know a lot about nutrition. if I may be nosey, what is your diet like on a typical day (meal by meal)?

  51. Monique says

    Hi Chris,

    Thanks for the information in this article. Very helpful! Just curious about one thing…I am considering making fish stock from the heads and bones of fish, as I read that this would be a great source of iodine and other minerals. Hoping to boost a sluggish thyroid. I am able to get heads and bones from a local (New England) fish monger for making the broth, but I wonder about whether this would be a healthy choice, given the presence of some toxins in the fish. More specifically, I wonder if a daily cup of homemade fish stock is excessive exposure, if the toxins are concentrated in any way by slowly simmering the fish heads and bones making broth more toxic than the meat of the fish itself, and whether toxins accumulate more in the thyroid, brains, etc. of the fish as they do in the fat of the fish. Any thoughts you might have on the overall safety of fish stock would be much appreciated!

  52. Mike says

    Chris, this line:

    “The highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals” is misleading.

    is misleading. If you look at the original source, which is called “INTAKE OF DIOXINS AND RELATED COMPOUNDS FROM FOOD IN THE U.S. POPULATION,” the authors state that fish only contributes 9% of total dioxin intake because Americans tend not to consume a lot of fish. There are two graphs in this same paper showing that freshwater fish and butter have staggering levels of dioxins.

  53. Alice says

    Hi there,

    Are there any reliable charts that categorise fish and seafood in terms of their levels of mercury?

    Thanks

  54. Helder says

    Seafood is just right for a healthy life style.
    Environmentalist left wing nut and New York Times are part of the head of lies when it allows the publication of distorted information.
    I love seafood and its so healthy

  55. Natalie says

    Good article, but you forgot to mention that some people don’t have the ability to detoxify. Heavy metal detoxifications are much more complex than binding minerals like mercury and selenium, it involves lots of pathways. If you have something like GI issues, metabolic imbalances, a stressed liver, or a weak immune system, just to name a few, your body might not be able to excrete that mercury.

  56. Ian says

    “The following chart illustrates the relative levels of selenium and mercury in commonly eaten ocean fish:”

    I do wish people would put relevant units on stats graphics!

  57. Frank says

    Hi there, a new study came out half a year ago, showing that seemingly the protective effect of Selenium found for rats in the study you cite, does not protect childbearing women as the IQ of there offspring significantly dropped with the amount of fish consumed:
    http://www.sciencedirect.com/science/article/pii/S027869151100576X
    adding the problems concerning the PCBs, as noted above by Daniel, I would not advise to rely on fish during pregancy but rather taking algeal DHA supplements.
    Kind regards,
    Frank

  58. Jess - biologist says

    This article is quite misleading. Fish are in fact a significant source of PCB’s, dioxins, and heavy metals. You shouldn’t write articles that could effect peoples health if you don’t know what your talking about. People need to be aware that you shouldn’t eat top predator fish like swordfish. Vegetables are not a significant source of toxins typically speaking. The comment by Daniel is very good, sure fish are good for you, but you need to be smart about what types of you eat and how often. You can’t just advocate fish as being a care free healthy choice. I disagree that it is all hype – I have measured mercury in fish and the levels would astound you. Be smart people, don’t believe everything you read, especially in this article.

  59. Michele Duncan says

    Can you review the research on overfishing and the state of the World’s ocean. I’ve read research that overfishing is causing more harm to our oceans, specifically coral reefs, than oil spills. This seems to never get main stream media attention. For environmental reasons, I lowered my intake of Omega 6′s, increased flax seed to improve the balance which is more important.

  60. Jake Ivey says

    Chris,

    Great article.

    But I post to request that you date all your articles on your website and elsewhere. It’s important for us, even professionals like me, to know when something was written.

    Thanks.
    ~~~

  61. Mark says

    Cancer estimates also assumed lifetime salmon consumption of 1,000 mg/d of EPA & DHA (four 6-oz servings of wild salmon every week for 70 years). Of course virtually nobody in the U.S. currently eats this much salmon.”of course virtually no on in the US currently eats this much salmon in a week”

    I easily eat this much wild salmon in a week. Considering a lot of people eat about 21 meals a week, four meals of salmon doesn’t seem unreasonable.

    • FerrisWheel says

      What about the radioactive waste being spewed out of Fukushima. It gets diluted, I agree, but long term consumption will have an effect. Go with Atlantic Fishes only!

      JMHO

  62. jess says

    Hi Chris
    This article brings up the issue of fermented cod liver oil again. Many nutritionists now recognise that FCLO is rancid and wont use it. I know you value it for the fat soluble vitamin content, but I still don’t understand why you would recommend it when it’s oxidized?

  63. Viola Toniolo says

    My biggest issue with any fish consumption is sustainability. Most of our oceans have been depleted of large fish (“fishing down the food web”), and marine ecosystems in general are pretty trashed worldwide (with the exception of the Ross Sea, Antarctica, which we are just starting to fish more extensively). Certification and watchdog programs like the MSC (Marine Stewardship Council) and SeafoodWatch are not necessarily relying on science to make their recommendations. The MSC is notorious for being highly influenced by the fishing industry, and SeafoodWatch just green-listed Chilean Sea Bass, which no scientist who studies this species or its ecosystem would ever recommend fishing commercially (they are long lived, slow to reproduce, and have already shown a huge population crash in the Southern Ocean). Furthermore, farmed fish is almost completely unsustainable by definition, because you still have to fish the small fish to make the pellets that feed the farmed fish (the entire anchovy and sardine fishery off the coast of western South America is in peril because of farmed salmon). Pellets are also often mixed with GMO corn or soy, which I’m sure isn’t ideal from a nutritional perspective.

    Chris, I would be delighted if you could address this topic in the context of recommending fish consumption, and stress the importance of obtaining sustainable fish. I think it can be done, but relying on SeafoodWatch and the MSC is not enough. In the San Francisco Bay Area we can join seafood “CSAs” like Siren SeaSA or Fair Share of Sea Forager who purchase directly from small boats, which are by definition fishing more sustainably than most, but how does one obtain sustainable fish in places where there is little access to this kind of program?

  64. Lisa says

    Hi Chris,

    You do amazing work, and I appreciate you approach! I find your articles and podcasts very informative and have already changed the way I eat. I was wondering what suggestions you have regarding avoiding or reducing radiation while increasing fish consumption in light of the ongoing Fukushima situation. Also, do the risks of eating regular canned sardines (bpa, etc) outweigh the benefits. I’m on a budget and the “organic” canned sardines are 3.5X the price. Thank you!

  65. Luca says

    FYI Brazil nuts are the highest in selenium also an easy way to increase selenium levels just 2-3 of them is enough a day…..

    • Terry says

      Hi, Unless I’ve missed it, with all this talk of mercury, no one has mentioned chlorella. It is one of if not the best methods of ridding the body of mercury. I started taking it 10 years ago after finding my mercury fillings were almost killing me. Had them all removed and have never looked back. I have to say though, the side effects of mercury being removed from the system are truly horrendous, but it has been worth it.

  66. Susan says

    Is it safe to eat Crustaceans during pregnancy? I am thinking yes, since they are at the bottom of the food chain and have less methylmercury compared to other fish. But I would like some clarification. Thanks!

  67. Megan says

    I’m almost 18 years old and I consume fish 3 or 4 times a week, mostly wild sustainable alaskan salmon. Is this fine?

  68. Rebecca says

    I too, am wondering about the issue of radiation and other toxins in the fish besides mercury. Also, what is the best source for Tuna?

  69. Ian Gillson says

    Well, I eat 5-6 cans of fish a day. With oats for breakfast and salad for lunch. Over the past 12 months I have lost 115lbs in weight and have managed to come off my BP and cholesterol meds. And I am in great shape. So I pay my money and takes my chances…

  70. David Hammond says

    Hi Chris,

    Personally, I am not convinced that the high levels of mercury in fish such as tuna and swordfish are safe even if they exist in the presence of equimolar or higher concentrations of selenium.

    The definitive study on this issue is Chang’s1, in which 16 kittens were fed a diet of tuna containing 0.3 to 0.5 ppm mercury, plus supplementary nutrients and vitamins. After a period of seven months, two of the cats had mild ataxia and one had severe ataxia. The cats were sacrificed at 11 months and autopsy revealed extensive liver damage including damage to the mitochondria. In this case the selenium in the fish was not protective.

    I agree with Dr Ralston’s statement in his review, Mercury: selenium interactions and health implications2, where he says “the ‘protective effect’ of selenium against mercury exposure may actually be backwards. Mercury’s propensity for selenium sequestration in the brain and endocrine tissues may inhibit formation of essential Se-dependent proteins (selenoproteins). Hence selenium’s ‘protective effect’ against mercury toxicity may simply reflect the importance of maintaining sufficient free selenium to support normal selenium-dependent enzyme synthesis and activity.” But even maintaining optimal levels of selenium may not be enough to completely nullify mercury’s toxic effects.

    In the same review he mentions the study by Friedman into the protective effects of dried swordfish on methylmercury toxicity in rats. He states that rats fed a diet of swordfish and methylmercury showed no signs of neurotoxic effects, while rats fed a control diet spiked with methylmercury without swordfish did. Dr Ralston attributes this to the protective effects of selenium.

    In spite of the proposed protective effect of selenium, both the control group and the experimental groups died, at 4.6 and 5.3 weeks respectively. It should also be noted that the control diet included 15% casein which has been shown to reduce mercury excretion in rats3, and thus may have exacerbated the effects of mercury toxicity in the control rats.
    These studies do not take into account the long-term effects of mercury exposure. The lower the dose of mercury, the greater the delay in the manifestation of symptoms. Deborah Rice fed monkeys a diet which included 50 micrograms of methylmercury per day for 7 years4. After cessation, blood levels quickly dropped to normal. When the monkeys were tested at 13 years of age they displayed clumsiness and loss of fine motor skills as well as decreased sensitivity to touch. Humans are exposed to mercury for decades and have longer to develop overt signs of mercury toxicity.

    One of the problems with the studies from the Seychelles and the Faroe Islands on the effect of methylmercury on neurodevelopment is that they rely on hair testing of mercury levels. This is often accurate, but does not take into account the fact that mercury disrupts cellular transport due to its affinity for sulfhydryl molecules. These molecules often form the active site in cellular transport proteins. Mercury binds to these active sites, altering mineral transport. This can result in hair readings for mercury and other toxic elements that are artificially low. Thus children with high exposure may actually be classed as having low exposure. Hair analysis actually provides a measure of how much mercury is being excreted. The most important factor is how much mercury is being retained in the body – but that is difficult to measure.

    Amy Holmes found that autistic children, even though they had higher exposures to mercury through their mothers’ dental amalgams and Rhogam injections, had lower levels of mercury in their hair, implying a reduced ability to excrete mercury5. The following hair test illustrates the ability of mercury to disrupt mineral transport in a child with ADHD and a weak immune system – http://www.livingnetwork.co.za/files/hairtest_564.pdf

    This is clearly an abnormal distribution of elements (all except one of the essential elements are below the 50th percentile) associated with a low reading for mercury.

    It may be safe for some individuals with optimal antioxidant and metallothionein status to consume tuna and other high mercury fish, but I think for many it would be safer to stick to fish such as sardines and salmon, which have high levels of omega 3s, but much lower levels of mercury.

    Thanks,

    David Hammond
    author – Mercury Poisoning: The Undiagnosed Epidemic.

    References
    1 Chang, L. W., & Yamaguchi, S. (1974). Ultrastructural changes in the liver after long-term diet of mercury-contaminated tuna. Environmental Research, 7(2), 133-148.
    2 Raymond, L. J., & Ralston, N. V. (2004). Mercury: selenium interactions and health implications. Seychelles Medical and Dental Journal, 7(1), 72-77.
    3 Rowland, I. R., Robinson, R. D., & Doherty, R. A. (1984). Effects of diet on mercury metabolism and excretion in mice given methylmercury: role of gut flora. Archives of Environmental Health: An International Journal, 39(6), 401-408.
    4 Rice DC. Delayed neurotoxicity in monkeys exposed developmentally to methylmercury. Neurotoxicology. 1989 Winter; 10(4):6450-50.

    • gh says

      I agree that some people should limit their consumption of fish and avoid those with higher mercury content. There’s plenty of anecdotal and clinical evidence of people becoming mercury toxic from eating fish. I question selenium binding to mercury in the fish, making the mercury no longer free to bind to anything else. Can this ‘new substance’ [what is this substance?] be cleaved apart in the gut? Are there other things in the body which mercury has a greater affinity for causing it to release this new substance and bind to other things? People with systemic illnesses that have low glutathione (GSH) among other things, have less GSH available to make glutathione peroxidase (GPx). The presence of adequate selenium does not mean there will be enough GPx to deal with the mercury. Often people with low GSH will have polymorphisms which reduce their bodies ability to make GSH. Often GSH is depleted because of a higher demand for GSH to detox products from systemic infection. Often there is a blockage in GSH production that has happened over time. Non-denatured cysteine is usually low in such people. Cysteine is considered a rate limiting factor in GSH production. Cysteine is also needed to metabolise most forms of selenium to selenocysteine so that the body can use it to make GPx. So the bodies of people who are low in GSH will usually be unable to utilise the selenium as much as those with enough non- denatured cysteine. People with low GSH should avoid fish higher in mercury, and limit their intake of most fish.

  71. Carol M. says

    Chris you are THE MAN. Thank you for your very concise, pithy articles that cut right through the bull. The warnings that discourage people from eating fish remind me of my dentist, who in his latest newsletter discouraged patients from eating nuts because they might break their teeth (as if it’s better to eat Twinkies!) . . . Anyway, your article hits the nail right on the head. THANK you!

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