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5 Reasons Why Concerns about Mercury in Fish Are Misguided


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selenium mercury, mercury in fish
Mercury content in fish has been a health concern for many years.

In 2004 the EPA and FDA published new guidelines suggesting that pregnant women (and those who might become pregnant) limit their consumption of fish to 12 ounces (340 g) per week due to concerns about mercury exposure.

These guidelines, which were only intended for pregnant women for the sake of their developing children, have quickly become an accepted fact among the mainstream media, the medical establishment, and the general public. They have also been indiscriminately extended to other populations, including men and women who are not pregnant. I frequently have patients that tell me they’re limiting seafood consumption due to concerns about mercury, and it seems like there’s a new study or media story on this topic every week.

But is it really true that eating fish increases the risk of harm from mercury—either for the developing children of pregnant women, or anyone else? Should pregnant women be limiting their consumption of fish for this reason? And is it possible that that pregnant women might actually be harmed by following the FDA/EPA guidelines?

Are you limiting fish intake due to concerns about mercury? Find out why you might be doing more harm than good. #fertility #pregnancy #kidshealth #myths #truths

I answer these questions in detail below. This article will be longer than usual; it’s an important topic and I want to give it the attention that it deserves. For the time challenged among you, here are the key points:

  • There’s no evidence that pregnant women or children (or anyone else) will be harmed by eating more than 12 ounces (340 g) of the most commonly consumed varieties of fish.
  • In fact, there’s a lot of evidence that eating less than 12 ounces a week of fish could cause significant harm to both pregnant women and young children.
  • Most pregnant women need to eat more fish, rather than less.

That’s the summary. Now let’s look more specifically at 5 reasons why you shouldn’t take conventional advice about mercury in fish at face value.

#1: Studies of Mercury Exposure in Fish Consistently Ignore the Important Role of Selenium

We’ve known about the role of selenium in preventing mercury toxicity for at least 45 years, with the first research report on this topic appearing in 1967. (1) Since then several studies have shown that selenium consistently and predictably counteracts the adverse effects of mercury exposure. (2)

How does selenium do this?

Exposure to mercury is harmful because it deactivates special selenium-dependent enzymes—called selenoenzymes. Since the brain consumes nearly 25% of the oxygen we breathe, it continuously produces oxygen by-products that can damage the fats and proteins that make up the brain. Selenoenzymes are extremely important in the brain because several of them prevent oxidative damage while others actually reverse it.

In the past, researchers thought selenium was protective because it binds to mercury and prevents mercury from harming other molecules. This led to the mistaken idea that mercury causes harm in the body until selenium binds it. But our current understanding is almost the reverse: it’s not that selenium prevents mercury toxicity by binding to mercury, but that mercury interferes with selenonzyme function by binding to selenium. In fact, mercury cannot cause harm until it occurs in high enough amounts to inhibit a significant percentage of selenoenzyme activities. Mercury is only harmful because it binds to selenium and prevents it from performing its vital roles in the brain.

As long as you are eating fish that contains more selenium than mercury, the amount of selenium in the body will always be in plentiful excess of mercury. That means that these essential selenoenzymes are never inhibited to a meaningful degree. Fortunately, the vast majority of fish most people consume have more selenium than mercury. The exceptions are pilot whale, shark, tilefish, king mackerel and swordfish.

Unfortunately, the well-documented protective effect of selenium is consistently ignored in both the medical community and the media when reporting on potential harms from fish consumption. This is almost certainly causing harm, as it has led to advising pregnant women and young children to eat less fish, when we should instead be telling them to eat more.

#2: The Evidence Suggesting Harm from Consuming Seafood Is Weak, and Doesn’t Apply to the Fish Most People Consume

There’s no question that mercury is a potent neurotoxin, and that significant exposure can lead to problems in both children and adults. For example, catastrophic pollution from a chemical plant in Minamata Bay in Japan caused severe toxic effects in the local population during the 1950s and 1960s. (3)

But does that mean that eating seafood which contains mercury is harmful? This idea comes primarily from a study performed in the Faroe islands, which are located approximately halfway between Norway and Iceland, and another performed in New Zealand. (4, 5)

The Faroes study is problematic for several reasons. First, it examined the neurological and developmental effects of maternal consumption of pilot whale meat, (the source of the bulk of their total mercury exposure), and found that eating ocean fish actually protected against the adverse effects that were noted. Even if the blood levels of mercury observed in this study were associated with harm in developing babies (which is debatable, as I argue below), such low exposures were not expected to be harmful to adults and no harms were observed in adults. This is because adults have plentiful reserves of selenium throughout their bodies and in their brains that help protect their brain selenium levels from being depleted. It is only when these reserves are depleted that oxidative damage can begin to occur. Developing babies are more vulnerable because they have no stockpiles of selenium to protect against mercury.

Second, the “adverse effects” observed in this study were extremely subtle. The magnitude of the effects noted were on the order of one finger tap slower than an unaffected child in a test which measured how many times the child could tap in ten seconds. (Tap one finger as fast as you can on your computer keyboard or mobile device and you’ll get a clear idea of just how subtle this effect was.) What’s more, the children who had the highest whale meat exposures were primarily from rural areas, whereas the unaffected kids were from urban areas. It is possible that factors other than mercury exposure may have differed between the two groups (e.g. socioeconomic status, home environment, having to wake up earlier and drive a long distance to the test site, etc.), and those factors may have influenced the results instead of their mercury exposures.

Third, over 85% of the seafood consumed by pregnant women in the Faroe Islands study was pilot whale meat. Earlier in the article I mentioned that pilot whale meat is one of the few species of seafood that contains more mercury than selenium, and thus would be expected to cause harm. Pilot whale meat is also much higher in other environmental toxins like cadmium, PCBs, and dioxins. A lot of toxins can accumulate in a 5,000 lb. whale during its 45–60 year life at the top of the oceanic food chain.

The New Zealand study was also problematic. Its results were highly dependent on whether or not a single child was included or excluded. (6) That child had by far the highest blood mercury content, but also was a high achiever. Including that child made the study results insignificant, but excluding the child made the study results significant. When the results of a study depend significantly on a single subject, that throws the findings into doubt. In addition, selenium deficiency was quite common in New Zealand at the time this study was performed—they were one of the most selenium-deficient nations on earth at that time—and the take-out “fish and chips” consumed by New Zealanders in the late 1970s included fish such as sharks—which like pilot whale, are one of the few species of seafood which contain far more mercury than selenium. (7)

What these studies tell us is that consumption of seafood that is high in mercury and low in selenium by pregnant women is potentially harmful for their children, especially if overall selenium intakes are low. They do not indicate that consumption of commonly eaten seafood with more selenium than mercury cause harm to pregnant women, children, or anyone else.

#3: Studies of Pregnant Women Consuming Seafood Show Benefits, Not Harm—as Long as the Fish Contain More Selenium Than Mercury

There are four major studies that have evaluated the effects of maternal mercury exposure from seafood on subsequent child development. I discussed two of them above, and showed why they do not apply to most people who eat fish. That leaves two studies: one performed in the Seychelles Islands (northeast of Madagascar), and another in the UK. (8, 9)

The Seychelles and UK studies found no adverse effects from consuming seafood. On the contrary, the UK study indicated substantial benefits from increasing maternal fish consumption, and noted neurological and developmental impairments among children whose mothers had avoided fish consumption. These studies are better indicators of the effects of seafood consumption for pregnant women, because outside of a few areas like the Faroes, most seafood that is commonly consumed in the U.S. and around the world contains far more selenium than mercury.

At least one US study confirms the beneficial impact of maternal seafood consumption. Researchers examined the effects of prenatal mercury exposure in a group of women living in Manhattan at the time of the World Trade Center disaster. The women who ate more seafood did have higher levels of mercury in their umbilical cord blood, but that did not translate into worse outcomes for their children. On the contrary, consumption of seafood during pregnancy was associated with significant benefits in motor development and verbal and total IQ. (10)

Once again, we see that the effects of consuming seafood that contains less mercury than selenium are not comparable to those of consuming seafood with more mercury than selenium.

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#4: Advising Pregnant Women (And Everyone Else) to Reduce Their Fish Consumption Is Not Harmless

If eating fish only exposed us to mercury without offering any benefit, we wouldn’t be having this conversation. Unfortunately, that’s far from the truth.

In the UK study I mentioned above, while the researchers did not find harm in consuming more than 12 ounces (340 g) of fish per week, they did find that consuming less than that amount was associated with significant impairments of communication skills and verbal IQ at six and eighteen months of age, and continued on throughout their adolescence (these children are now ~20 years old). This study was by far the largest (14,000 mother-child pairs), best designed (multiple evaluations performed and repeated throughout life), and best controlled for other factors such as socioeconomic, educational, and a host of other potentially pertinent factors. They found the worst effects were observed in children whose mothers ate no seafood at all during their pregnancy (about 12% of the study population).

This should not come as a surprise. A large number of studies indicate that lower intake of long-chain omega-3 fats (found in fish) during pregnancy is associated with growth retardation, delayed or suboptimal depth perception, lower scores in tests which measure neurodevelopment, deficits in fine motor skills, speed of information processing in infants, and irreversible deficits in the release of key neurotransmitters like serotonin and dopamine. (11)

What’s more, it’s likely that both the benefits (from consuming more seafood) and harms  (from consuming less seafood) that were observed in the UK study would be amplified if it was repeated here in the US. The ratio of omega-6 to omega-3 fats in the US is significantly higher than it is in the UK. A high intake of omega-6 fats limits the conversion of short-chain omega-3 fats into their longer-chain—and far more important, from a health perspective—derivatives like EPA and DHA. This makes it even more necessary for pregnant women (and others) in the US to obtain these beneficial long-chain omega-3 fats directly from food. And guess what the only significant dietary source of these fats is? That’s right: seafood.

Finally, in addition to the data I mentioned above linking higher intake of omega-3 fats to better neurological and developmental outcomes in children, there is evidence that fish consumption is beneficial for adults. Studies have shown that even modest fish consumption (1-2 servings of cold-water, fatty fish like salmon per week) are associated with a 36 percent decrease in deaths from heart disease, and a 17 percent reduction in deaths from all causes. (12) For more on the benefits of eating fish, see my article “Is Eating Fish Safe? A Lot Safer Than Not Eating Fish!”.

#5: Ignoring the Protective Effects of Selenium Underestimates the Risk of Eating Some Fish

Although most ocean fish contain far more selenium than mercury, the selenium status of freshwater fish is much more variable. Mercury tends to accumulate in fish in lakes where selenium availability is limited. That leads to a double-whammy where some freshwater fish have relatively high mercury levels along with low selenium levels. This may explain why adverse effects were observed in a study of freshwater fish consumption in Finland, a country notorious for its poor selenium status, and was so low that it became the first nation to add selenium to its fertilizers. (13)

It’s important to note that even when total mercury levels in fish are below the recommended safety limit, consuming these high mercury, low selenium fish may still cause harm to consumers. In other words, it’s the ratio of selenium to mercury in the fish (known as the “selenium health benefit value or; HBVSe”)—rather than the absolute amounts of either—that determine whether it is safe to eat.


As the evidence above indicates, aside from the warnings to avoid shark, swordfish, tilefish, and king mackerel (varieties which can contain far more mercury than selenium), the EPA/FDA advice to limit fish consumption during pregnancy is not only unfounded, it is potentially harmful. From a public health perspective, pregnant women should be eating more fish—not less.

There is one reason, however, that I’m concerned about advising people to increase their fish intake: the environmental and social impact. To meet even the EPA/FDA guidelines for maternal fish intakes—which as I’ve argued in this article, are likely too low—would require a doubling of per capita fish intake in the US. Yet ecologists have warned for years that the exploitation of global fisheries at the current rate is not sustainable without massive conservation efforts. (14) Many fisheries are either completely exhausted or in significant decline, and pressure to increase fish consumption may exacerbate this problem if it’s not done in a sustainable manner.

This is a big problem—the elephant in the room when it comes to discussions about the health benefits of seafood consumption. As with many similar predicaments, there is no easy solution.

I’m continuing to research the issue and will report back soon. In the meantime, I suggest using guides such as those published by the Marine Stewardship Council and The Monterey Bay Aquarium to choose only the varieties of fish that are being harvested sustainably. Fortunately, many of the most sustainable choices (e.g. sardines, anchovies, mackerel, wild-caught salmon, etc.) are also the fish that are highest in the beneficial long-chain omega-3 fats.

I’d like to thank Dr. Nick Ralston for his generous guidance and contributions to this article.

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  1. Very interesting, but like many others I am wondering about
    canned tuna? Also, I think there are large populations here and in other countries that live inland and are not true
    fish eaters. It doesn’t seem reasonable that these people with long histories of not eating much fish would be at risk health wise? Thanks for replying to so many questions.

  2. I have been limiting fish because I am concerned about fish coming from other countries, who don’t have the same safety guidelines as the US.
    What are your thoughts on fish from China, Vietnam, etc.?

  3. Another great article/discussion, thanks! My concern is not so much the mercury, I am now scared of radiation (from Japan) and the polluted quality of plastic eating fish.

  4. Thanks for this.

    Is there a reason to avoid wild caught pacific fish because of Fukushima? I keep hearing this, but I only eat wild fish, mostly Pacific, so this limits any fish I can find. What are your thoughts on effects from Fukushima on fish?

  5. This is utter nonsense. There is absolutely no provable scientific analysis behind any claims about safety. Do you understand how to actually create a scientific experiment and then how to interpret the results?

    I like some of your writings but you are way out of your league on some of the others. This is one such example. Citing other inconsequential research or falsified research doesn’t make any statement accurate.

    • Your critique is not substantive or specific, so it’s difficult to take seriously.

  6. I think this is an excellent topic of discussion because of the significant importance of omega 3 EFAs in the body and especially during pregnancy. However I believe there is some misinformation in this article and some important missing information as well. I believe the issue is made out to be not eating enough fish when the real issue is not this at all, it is being sufficient in omega 3 essential fatty acids.

    Is the statement that “In fact, mercury cannot cause harm until it occurs in high enough amounts to inhibit a significant percentage of selenoenzyme activities. Mercury is only harmful because it binds to selenium and prevents it from performing its vital roles in the brain.” really true? I have my doubts. First mercury not only targets the brain, but also the central nervous system, the kidneys, the liver, the heart, the pituitary, the thyroid, and the GI tract. There is plenty of evidence that mercury can cause harm to many places in the body not just the brain as this statement implies and mercury binds to other biologically active components of the human body than just selenoenzymes. For example mercury can also bind to cell membranes and disrupt cellular function in that way. So, I dont think this statement is correct, though I am not 100% sure.

    Mercury is the second most toxic metal known to man (right after plutonium) and comes in four forms: Elemental Mercury (Hg), Inorganic Mercury (Hg2+) (when elemental mercury is oxidized and loses two electrons, it is a salt), Methyl Mercury (MeHg) (comes from bacterial synthesis of inorganic mercury), and Ethyl Mercury (EtHg) (a synthetic man made organomercurial form similar to MeHg). These all have very different reactions in the body in the way they are absorbed, where they are absorbed, and the types of damage they inflict. The type found in fish is Methyl Mercury or more correctly Methyl Mercury Cysteine. This is important to know in this discussion.

    Unlike other forms of mercury, methyl mercury cysteine is 95% absorbed in the gut and because it is bound to cysteine (which is a mimic of methionine) it can get everywhere in the body crossing the blood brain barrier and the placental barrier. MeHg is highly toxic to cells and causes massive cellular dysregulation and malfunction. It can also break down into toxic inorganic mercury, Hg2+, and do its damage in that form. This is of course if MeHg is not stopped by something like selenium, or chlorella, or alpha-lipoic acid.

    There are recent studies that show selenium rich fish do cause mercury toxicity harm. Here is one such study: http://www.hindawi.com/journals/bmri/2012/681016/. It is a study on mice, but is still concerning. I looked at some of the studies chris references and cannot tell who sponsored them, but studies are never perfect, they are sometimes wrong, sometimes not done well, and sometimes are influenced by money, profits, corporations.

    When consuming fish it is important to note the difference between farm raised fish versus wild-caught fish. There is a big difference and people should avoid farm raised fish for many reasons I wont go into, there is plenty of info on the web about this.

    Although fish and fish eggs are probably the best source of omega 3’s, there are good effective supplemental forms, including krill oil, distilled pharmaceutical grade fish oil (e.g. carlsons), fermented fish oil, and concentrated algae forms. Although there is some evidence that krill oil can be contaminated with arsenic, so may not be the best choice. If Krill is clean, however, it is probably even better than fish for omega 3s and is in fact probably the best bioavailable source in existence. And, though somewhat debatable, krill is almost certainly a sustainable source. Also, there are very rich vegetarian sources (flax, chia, sacha inchi) of ALA, which can be converted up to about 10% into DHA/EPA. I know some people thrive on ALA sources of omega 3s, but for most people, ALA sources will not result in omega 3 sufficiency. So it is simply not correct to say fish is “the only significant dietary source of these fats”.

    In my opinion, pregnant women should absolutely limit fish, but not omega 3s and I think that distinction should have been made here. Why would a woman want to consume something that is potentially harmful (there is always a possibility because MeHg does cross the placental barrier)? Studies arent perfect. A pregnant woman can get all the omega 3’s she needs from clean fish oil or clean krill oil. Moreover, omega 3’s from any source should always be consumed with antioxidants and coconut oil for greater effectiveness and oxidation prevention. Krill oil will actually not oxidize in the body, unlike fish oil.

    I think the bottom line here is that the real issue for a pregnant woman is to make sure she is consuming plenty of omega 3 oils (especially DHA and EPA) not that she is consuming plenty of fish. Fish is one source and a very good source, but the fact that fish contain not only mercury but can also contain PCB’s and dioxins means they pose a potential risk of causing damage to the fetus. And moreover, the mercury toxin level is increasing, it is not decreasing. Even if the risk is small with selenium rich fish, why take that risk unnecessarily? I think advising anyone (especially a pregnant woman) to eat lots of fish is just not a good idea. On the other hand advising everyone (especially pregnant women) to consume sufficient omega 3 oils is what should be being advised.


    • Thanks for your thoughtful comment.

      I am familiar with the study you linked to and have discussed it with Dr. Ralston, who made several of the observations I’m sharing in this response. Though at first glance it does seem to suggest harm from mercury in seafood, upon closer inspection it raises more questions than it answers. The diets which where supplemented with fish contained slightly less (~7%) less mercury, than the “MeHg” diets, but the mercury levels in all brain tissues were 35 +/-10% lower in mice that were fed diets supplemented with fish.

      In Figure 1, you can see that there was no observed effect of MeHg on the outcome they monitored, but those fed fish were adversely affected. If the harmful effects were due to mercury, we’d expect to see higher levels of mercury in the brain tissues of affected animals. Yet this is not the case; in fact, there was more MeHg in the brain tissues of animals that were less affected.

      There’s a rule of thumb in toxicology: “the dose makes the poison.” Either it’s true that the mercury in the fish caused the adverse effects, in which case we have to ignore this fundamental tenet of toxicology, or there is some other reason that animals eating the fish were harmed.

      What could that reason be? More investigation is needed, but we know that mercury the H. aimara (wolf fish) is an ambush predator that grows to body weights as big as 40 kg. It’s one of the “river monsters” that appears in the TV series of the same name. Like all apex predators, it bioaccumulates persistent bioaccumulative toxicant (PBT) agents that enter its ecosystem. These include mercury, but also many other organic and inorganic toxins. It seems more likely that one of these toxins accounted for the harm, since mercury levels were lower in the brains of affected animals than those that weren’t affected.

      As I mentioned in the article, so far the major studies that have been done on the effects of maternal seafood consumption involving species with a positive selenium/mercury ratio have found only benefit to the developing baby (and mother). As always, I’ll continue to evaluate the research as it is published and if I see a need to change my recommendation, I will.

      Finally, there are nutrients in fish (like vitamin D, selenium, and highly absorbable protein) that are not found in fish oil. I do not think they are equivalent.

    • i had Mercury toxicity in 2004 due to my 5 amalgam fillings. I was very ill from them. My legs were like stones and very heavy, I had no energy, headaches, knee and shoulder pain. And the pains travelled around my body from jaw to shoulder and turned up at a different place every day! After save removal I was treated by a natural holistic doctor in Germany. He used electro acupuncture according to dr. Voll. And we also detoxified using bears garlic (high amounts of sulphur). Neprorella algeas and a few other things plus liver and kidney support as we strengthened the detox organs. Yes Mercury crosses the blood brain barrier and I made the huge mistake in taking algeas while I still had filings in the mouth. My short term memorie was completely gone and I could not retain anything what people said to me 5 seconds after someone said something, this was very scary, however this only lasted for a few days.
      So we detoxified my body over several months and the machine was telling us how much Mercury was still in my body. In the end it was all gone. The arrow on the machine went lower and lower each time I saw him. I saw him every 2 weeks flying there from England, where I lived at the time. I just want people to know that it is definitely all reversible, so to not get scared. My brain is better then anyone’s I know of. I also take a lot of flax seed oil which really helps my brain too. I’m 38 now and look like 25. I only eat organic and no grains, sugars, pasteurized diaries… and cook my own food. That natural doctor was brilliant. 3 years ago I came to the U.S. and now I’m in a dilemma with having to eat all this US pseudo organic produce which is neither real raw nor organic. All eggs are put into bleach which is forbidden in Europe. I import my nuts from Germany as I can’t digest the (same) nuts here. The honey here even if it says raw is not raw. The word raw and natural are only marketing tools. I’m also convinced that organic here is not organic. Because I lived in 3 countries in Europe and we also had a big garden. Real organic food smells much stronger, and gets very wrinkly and withers away within 2 or 3 days!
      I came here 2012 and I heard that my natural (very successful) doctor, who healed a lot of people, died within 3 months!!! He was very healthy when I saw him last, which was in November and he was death by March! I’m sure he was killed.
      There was a doctor once found hanging (plus his secretary) because they found a cure for something. I’m sure the medical system is like the Mafia, like my 80 year old German elder friend told me. He saw over the last 30 something years all the things which helped him and his wife slowly be taken off the market!
      Same happens here too. Just that the USA is far more worse when it comes to food and much more corrupted!
      Anyway, he healed me from mercury poisoning and yes definitely you can get it out of your body and brain !!

  7. Great article. I would like to advise people that are interested in this topic to watch the award winning documentary FISH, MERCURY, AND FISH: THE NET EFFECTS. The documentary and other useful information can be viewed at http://www.undeerc.org/fish/.

  8. Hi Chris,

    Your podcasts and posts are amazing! But while mercury is a concern, PCBs and other toxins stored in fat that are also a major issue. See Marion Nestle’s book “What to Eat” as a reference – her chapter on fish is amazing and has pretty much 100% convinced me that it is neither sustainable, nor healthy to eat most species of fish. It goes far beyond just mercury, from my understanding, especially if you care about environmental sustainability…

    • I addressed PCBs and other toxins in fish in a previous article: http://chriskresser.com/is-eating-fish-safe-a-lot-safer-than-not-eating-fish

      Here’s an excerpt:

      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.

  9. Hi Chris

    Super interesting article! I also liked the fact, that you widened the scope a bit and talked about the ecologic and social impact. This really often is my concern when I think about eating more fish. Also thanks for the insight on freshwater fish. I live in a region in Germany where we have a good supply of rainbow trout, can you say anything about the selenium/mercury ration of trout?



  10. I’m pregnant and I haven’t reduced my seafood intake at all. In fact, I am trying to INCREASE it by making sure that I eat sardines for lunch at least twice a week (in addition to fish and shellfish for dinner a few times a week). My whole life my mom called fish brain food, and ate a ton of fish when she was pregnant with me. I, obviously, am brilliant, so there you go 😉

    • Same here. I eat a good canned sardine a couple of times a week, brazil nuts, canned Atlantic wild caught salmon every week or so and call it done. Getting all wrapped up in every detail and worry about this and other health details, frankly, has become soul-sucking (FOR ME–if you have issues, go for it with a bang so don’t go off on me here. LOL) but life awaits and I am partaking and backing off from all this in the future. 66 YO granny, feel great now, eat the best I can and don’t worry about it. I know what to do, will have an ear cocked for changes in Paleo (which is changing and that is good!!–Vegans seem stuck, doctrinaire and desperately searching for corroboration–which turned me off years ago when I was searching.) But these are MY own opinions. I had to stop and evaluate just how much time and money I was spending on obsessing on all this. People should decide for themselves–and I have. Chris does a super job and I respect what he is doing. About the “studies” you have to pick something, or you are just whipped around in confusion and worry and obsession. I am not a scientist–but in my years I have decided to trust what I feel and think, along with what I know already. I have to–I want to sleep at night. LOL. At 66 I do know that feeling good and good health is important and makes the rest of my life more fun and strong. That is the goal. The rest of my life outside of my diet and exercise being worthy and accountable and productive . Best and regards to all here!

  11. Hello Chris, this is a great article however, for many of us it is impossible to get or afford ocean fish. Most of the fish available in our area is farmed and farmed fish has been analyzed to have very low levels of Omega-3 fatty acids; farmed salmon are fed artificial Axtaxanthin which is toxic; and the chemical soup that farmed fish swim around in because of the waste material given off by the high concentrations of the fish in the cages is dangerous. It’s the same conundrum as with organic foods. We all know that they are better for us but who can afford them on a continuous basis? Ocassionally I buy them along with ocean fish but I’m sticking with eating mainly herring which is the highest in Omega-3 and the lowest in mercury and is also affordable. I also take a well distilled Omega-3 oil with independent lab analysis and eat brazil nuts and lots of onions for selenium. Thanks again for the great article. I will try to eat more wild caught salmon if I can.

  12. Chris – Love your articles! It’s awesome how you cut through the BS that reigns on other sites.

    Question – so if my selenium levels are adequate I DON’T need to have my amalgam fillings removed?


    • Laure,

      This is probably the first time I have disagreed with Chris’s assessment. Mercury is toxic, period. Amalgams are the worst. Your fillings MUST be removed by a properly trained dentist (search IAOMT), with proper detox protocol, as well…

    • My mom is 89 and in pretty good health. She’s had amalgam fillings since she was a teenager, and has had lots of other dental work besides. She also cooks in aluminum pots sometimes. What else can I say except that you can’t argue with success?

  13. Chris, you mention sardines, mackarel, wild salmon but what about tuna? Do most varieties of tuna have more selenium than mercury? Also what about the tuna and other seafood substitutes. I read an article that tested sushi restaurants across US and over half the fish they stated on menu (tuna, snapper etc) were actually another lower quality fish.

    Sushi is my favorite but my trust in most sushi establishments is low. Almost all of them use farmed salmon which is terrible and even when they tell me I can pay more for wild, I question it. I can usually tell when salmon is wild by the color and texture but now they are even using dyes to make it look like wild etc. When I order crab on the menu, I get pollock.

    • Tuna is high on the food chain, so its mercury levels are high as well. I’m not sure about the ratio, but given the high mercury levels, I would guess the ratio wouldn’t be too great. This Wikipedia article links to a bunch of articles you can read for more info: http://en.wikipedia.org/wiki/Tuna#Mercury_levels
      If the sushi you eat is from large predator fish, then it will be high in mercury too.

      Re salmon. I remember reading an article on Mark’s Daily Apple about different types of salmon farming. Farmed salmon wasn’t as good as wild, but there were definitely some types that were pretty good quality. I’ve actually found that farmed salmon looks and tastes better than frozen, though I eat mostly eat wild, for the health benefits. So I’m not sure how you are able to tell the difference between wild versus farmed, because by taste and look alone, the farmed actually seems to be much better quality, probably because they can manipulate feed and use dye to improve taste and texture. I definitely wouldn’t trust taste and appearance to guess whether salmon was wild or farmed.

  14. Thank you Chris for the great article! But I’m still a little confused…. isn’t there a problem with mercury accumulating in the body?

  15. Oh Chris, I can’t STAND the taste of seafood. Give me some good news…please? Is there any other way to get the nutrition?

    Thank you for your article! 🙂

  16. I totally agree that eating fish is a good idea and safe. But to add to the conversation – my dad is a deep sea fisherman who lives on Nantucket Island. He argues that politics have totally overtaken the fishing industry and some particular industries (particularly tuna) have influenced the numbers as far as the amount of mercury to selenium. He says that if they want good numbers, they just use small fish to get the numbers and ignore the large fish that have much higher mercury. He would still eat any fish – mercury or no mercury – but it is something to consider. He understands how fish pick up mercury and can see how that happens – but do you know how fish pick up selenium? We are not sure about that – and it would make a difference if the fish pick them both up at the same time. If you would like to talk to him about this in the furthering of your research – he would be delighted – as fishing is his life and his favorite topic of conversation. 🙂

  17. Hi Chris,
    What about the Fukushima Daiichi nuclear disaster and the levels of radioactive materials now in fish? Wouldn’t this be more of a problem than mercury levels and why we would advise to reduce fish consumption from these areas?

  18. Hi Chris,

    What would you say is a “safe level” of mercury?

    My Doctor’s Data test revealed a level of 21 for me, 11 for my daughter, both well above the 4 that the lab notes as the upper limit of “normal”. After removing the last couple of mercury fillings I will be doing a chelation but just wondering what you consider to be the normal range.