Doctor's Note

I’ve covered mercury in fish before in videos such as Nerves of Mercury, Hair Testing for Mercury Before Considering Pregnancy, and Fish Fog. For more on canned tuna in particular, check out:

What else can we do to protect our newborns? See:

But what about the long chain omega-3 DHA in fish—isn’t that necessary for healthy brain development? That’s the topic of my next video, Mercury vs. Omega-3s for Brain Development.

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  • Adrien

    It should be added by law on every canned tuna that “tuna consumption can shrink the brain of your child”. And if this industry “will suffer important economic loss”, and so WHAT ? The greater good for all.

    • Dikaiosyne

      No, such a notice shouldn’t be affixed to canned tuna–unless the effects of fish consumption upon fetal brain development are also seen in children who consume fish.

      • Adrien

        unborn child, or fetus to be more precise indeed.

      • Rich

        Today’s title is somewhat misleading: 1) mercury ingestion not fish has a material developmental effect. Canned Tuna being a known high mercury candidate. 2) The mercury ingestion evidently impedes fetus developmental brain size, NOT shrinking brain size.

        • Adrien

          Fish is the prime cause of mercury ingestion. I don’t know what is worst. If your brain shrink or if it does not develop, I don’t see the fundamental difference. Results are scary in either way.

          • Mercury Exposure

            according to the WHO (1991 & 2003) dental mercury fillings are the largest exposure to mercury in the population (who have them) – 120 million people

          • Adrien

            Interesting, can you source that info ? According to Dr Greger: One canned tuna a week is like having 29 amalgan in your mouth.


            not surprised that dental fillings can be the largest exposure to
            mercury when you don’t consume fish. But when you consume fish
            regularly, it’s a no brainer.

          • Mercury Exposure

            Hi Adrien

            Here is the link to WHO 2003, where they state “Dental amalgam constitutes a potentially significant source of exposure to elemental mercury, with estimates of daily intake from amalgam restorations ranging from 1 to 27 µg/day, the majority of dental amalgam holders being exposed to less than 5 µg mercury/day.”


            But a more recent Risk Assessment was done in 2010 utilizing the CDC’s NHANES dataset. It found that if using the EPA’s 20 year olf RfC (mercury safe limit) then 60+ million were over the safe level everyday just from 1 filling. But if the more recent Cal-EPA RfC was used (revised in 2008 to 10x lower) then all 120 + million are over the daily safe allowable dose.

            you can watch a video with the author of the study, Mark Richardson here


            This is the researcher Dr. Greger quotes in his Tuna Vs Amalgam article, which I did not agree with his conclusion. So I had Mark Richardson write a more comprehensive comparision and by far amalgam presents more risk because of higher exposure and it’s RfC is some 10 times lower than methylmercury

            a video with Mark explaining is here


            his write up comparing mercury exposure and toxicity of Tuna Vs Amalgam


          • Adrien

            Thanks for all the details. So the worst things will be to have mercury fillings and to consume regularly fish. And the least harmfull one will be to not having mercury fillings and to not consume fish at all.

    • Hollywood Resident

      Exactly….SO WHAT! So an industry that is poisoning people suffers economically, that’s a GOOD thing. Mercury poisoning is an ugly way to go, for adult or child. But your government spends taxpayer dollars to prop up industries that poison it’s own citizens, on the theory that industry is good and necessary, jobs are jobs. The Feds are too stupid to recognize that free market forces will level any disturbance in any industry, and capital will flow to where it’s most productive if honest information is not withheld. Because Doctors are self-interested, and refuse to even tell patients they’ll live longer and better without meat or fish, AND the Feds are protecting industries that are destructive to human life, the free market forces are being blunted, by deliberate misinformation from a government that only cares about being elected because of jobs reports… as for the people? Let them eat poison. Do us all a favor, hang a politician today.

  • Veganrunner

    I am speechless!

    • Coacervate

      You don’t say :)

  • unsure

    A quick question. On your graph you say the “body burden of canned tuna” – are these numbers based on Hair samples or serum samples? I know that the graph axis says Hair samples, but I’m always sceptical of such radical graphs. I wonder if the canned tunned numbers you plot don’t account for normal excretion.

    As a person who likes to watch the video without further reading I’m left wondering if you’ve compared two different measurements to make your argument look stronger.

    Sorry if I’m being stupid and nitpicking but with such a strong argument just wanted to be sure as you the describe the higher numbers as “body burden”

    Great video though, keep up the good work!

    • If you click on the Sources Cited link above you can read the studies yourself!

  • Hillary Rettig


    I read this and immediately thought of this:

    Life Magazine ran some tragic pictures of this

    • Dikaiosyne

      This is an *acute* instance of MeHg exposure and symptomatology.

  • Dikaiosyne

    Why in the world wasn’t this article titled “Fish Intake Associated With Fetal Brain Shrinkage”? As it stands, the current title suggests brain shrinkage for all fish consumers.

  • Seann

    I wonder if in the graph with the tuna, it showed eating a serving of sardines every two weeks. There are some seafood options that have low levels of mercury people can eat in moderation:

    • guest

      But high in arsenic and PCB’s, dioxins, etc.
      No way around it, sorry.

  • MaryFinelli

    With the many vegan seafood alternatives available, why not instead opt for them:
    They’re better for people, fish, and the environment.

    • Dikaiosyne

      “They’re better for people, fish, and the environment.”

      Can you cite a well-designed empirical study that supports this claim?

      • MaryFinelli

        There are many that address these issues. However, in a nutshell: It’s better for the fish because they’re not tortured and killed. It’s better for the environment because aquatic habitats aren’t wrecked in the quest for fish, which also harms and kills other aquatic animals, all of which degrades ecosystems. It’s better for people because, for example, they don’t ingest mercury, dioxins, and other toxins that bioaccumulate in fish tissues. All the nutritional benefits that can be derived from fish can be more safely, humanely and environmentally responsibly obtained from plant sources.

  • Judy

    I appreciate the tuna mercury info, but am really bothered by all the tuna I ate in the past. Is mercury held in the body or does it detox out?
    I also have a question about turning orange with eating a lot of carrots or carrot juice: one site says that it is the liver detoxing that causes the orange color and another place says it is in fact the carrots. What is your take on that?

    • Darryl

      Begerow, J., et al. “Long-term mercury excretion in urine after removal of amalgam fillings.” International archives of occupational and environmental health 66.3 (1994): 209-212.

      The long-term urinary mercury excretion was determined in 17 28- to 55-year-old persons before and at varying times (up to 14 months) after removal of all (4–24) dental amalgam fillings. Before removal the urinary mercury excretion correlated with the number of amalgam fillings. In the immediate post-removal phase (up to 6 days after removal) a mean increase of 30% was observed. Within 12 months the geometric mean of the mercury excretion was reduced by a factor of 5 from 1.44 μg/g (range: 0.57–4.38 μg/g) to 0.36 μg/g (range: 0.13–0.88 μg/g). After cessation of exposure to dental amalgam the mean half-life was 95 days. These results show that the release of mercury from dental amalgam contributes predominantly to the mercury exposure of non-occupationally exposed persons. The exposure from amalgam fillings thus exceeds the exposure from food, air and beverages. Within 12 months after removal of all amalgam fillings the participants showed substantially lower urinary mercury levels which were comparable to those found in subjects who have never had dental amalgam fillings. A relationship between the urinary mercury excretion and adverse effects was not found. Differences in the frequency of effects between the pre- and the post-removal phase were not observed.

    • doodeet

      You can get tested for your heavy metal “burden” – even hospitals have the ability to do this and are aware. Most holistic doctors can send urine and hair samples to see what your burden is currently. If heavy metals such as mercury and lead do not detox from your body, they leave your active system and bury deep into tissues/fat. This can make you very ill. Do not try to detox with those health food store systems. If you pull heavy metals back out into your active system too quickly, your body will not be happy! Mercury detoxing is done slowly to avoid this problem. Lead poisoning can be detoxed more quickly. I wish I had been tested before my pregnancies. Every single fish is contaminated now thanks to our commercial industries. The smaller fish with shorter life spans are safer to eat if you must. Larger fish with a longer life span are the worst!

  • Plantstrongdoc M.D.

    The point is that our food supply is heavily contaminated and bioaccumulation happens in animal products. Another reason to avoid (or seriously limit) intake of animal carcass

  • Bobby Ramos

    I eat fish 4 times a week with vegie n sweet potatoes is that ok or what, I don’t under stand, I thought fish was good for us is it???????.

    • Dikaiosyne

      It depends upon the type of fish:

    • Thea

      Bobby Ramos: I fully understand why you would think that fish is healthy. That misinformation is *all* over the media and internet. To learn the truth behind fish consumption, check out this nice NutritionFacts summary:

      Each of those links will take you to a NutritionFacts video that explains why again and again, we see that fish consumption is not good for us. Today’s video is just one more example.

      Good luck.

      • Dikaiosyne

        Yeah, fish consumption’s not good for us. That precisely why a 2013 Harvard study concluded a lower mortality rate in fish consuming adults:

        • Thea

          Dikaiosyne: And I have a study showing fish eaters live shorter lives.

          It’s never about one study. You can find studies that show that smoking has nothing to do with cancer. But the body of evidence, the mountain of evidence says otherwise.

          The same is true concerning fish. There is a mountain of evidence that eating fish – yes, all kinds – is not generally healthy for humans. (I’m sure a bite every couple of years would be fine. So, there is a line there somewhere. But we don’t know where the line is, and it is better to error on the side of caution – if not for your immediate health, then for your health as it gets effected when the oceans and planet dies.) That’s why I shared the link above. The link above takes you to a page containing a nice summary of just some of evidence against fish – and that summary is impressive just as is.


          If you aren’t Paleo Huntress herself, you are her identical twin. So, I’m leaving the conversation here. If you want to eat fish, go for it. May you live long and prosper.

          • Rich

            Thea – what is your study reference? The cited one is not insignificant.

          • Thea

            Rich: Even if the cited one is significant, I think my point is still valid. But I’m happy to share the blurb I have for whatever it’s worth. :-)
            from : PCRM
            Vegetarians Live Longer

            Vegetarian diets can extend life expectancy, according to early findings from the Adventist Health Study-2. Vegetarian men live to an average of 83.3 years, compared with nonvegetarian men who live to an average of 73.8 years. And vegetarian women live to an average of 85.7 years, which is 6.1 years
            longer than nonvegetarian women. This study is ongoing and includes more than 96,000 participants. The results further indicate vegan diets to be healthful and associated with a lower body weight (on average 30 lbs. lower than that of meat eaters), and lower risk of diabetes, compared with diets that include
            animal products.

            Fraser G, Haddad E. Hot Topic: Vegetarianism, Mortality and Metabolic Risk: The New Adventist Health Study. Report presented at: Academy of Nutrition and Dietetic (Food and Nutrition Conference) Annual Meeting; October 7, 2012: Philadelphia, PA.

          • Rich

            Thea – excellent, thanks for the reference.

          • Dylan Lenn

            Thea, I am trying to look up this supposed study but cannot find it.

          • Thea

            Dylan Lenn: I’m not an expert in finding studies. I just have that reference. Good luck!

        • Adrien

          It’s not the fish, it’s the long-chain ω-3 polyunsaturated fatty acids. Stuff that your body can make if you don’t binge on ω-6 oil and that you eat enough dark green leafy, walnuts and flaxseed. Study show that Vegan have more than 200% the convertion rate than omnivore. And let us remember than you can have the benefits of fish consumption without the risk (that cannot be separated otherwise – at least to my knowledge) using algae-based DHA supplements.

          Fish are unhealthy in part because they are polluted, and they are polluted because they live in the sea. It’s not because some fish are smaller that they magically become good for us. It just mean they are less toxic. Consider this: the sea was the biggest garbage of the world for more 50 years – and still today in many parts of the world. One example: the nuclear industry throwed 100 tons of nuclear waste into the sea before it was declared illegal to do so. And with Fukushima between 20 and 40 billions of becquerels just leak into the ocean.

          Still want to consume fish ? I don’t. Beside, we don’t need to eat fish for anything. Do you really want to drop mortality rate from CHD events (and many other like cancer) like the study you talk about ? Ever consider honesty being vegan ?

        • Darryl

          It appears that pescetarians (those who eat only fish, among animal foods), have comparable mortality, and perhaps a non-significant edge over vegans in the Adventist study II in overall mortality, though not in cancer mortality. I believe the best candidates for any pescetarian edge are B12 deficiency among vegans that don’t supplement, long chain ω-3 fatty acids, taurine (1, 2), and iodine.

          Dr. Greger recommends supplements for B12, EPA/DHA, and iodine. Vegan supplements (to exceed pescetarian intakes) for B12, taurine, and iodine are very cheap, EPA/DHA less so.

          Disregarding the health and animal welfare concerns for the moment, the world’s oceans are already overfished, and we couldn’t feed but a fraction of the current population on a pescetarian diet, much less all 9 billion of us mid-century. If we can get the benefits without consuming heavy metals and persistent organic pollutants, or sending fish populations into long-term collapse (the Grand Banks cod fishery still hasn’t recovered, two decades after being closed), why take the personal and global risks?

          • Adrien

            @ Darryl “Vegan supplements for B12, taurine, and iodine are inexpensive (< $10/year total)" Please share if you know one product containing those nutriements with this price. Aside Dr. Fuhrman’s Men’s Daily Formula (with B12, taurine, iodine + D3 and K2 which is at best 198$/year) and the possibility to buy cheap B12. I'm desperate to find one good not expensive supplements without folic acid.

          • Darryl

            liquid methylcobalamin: 53 years at the RDA, 1.3 years at Dr. Greger’s recommended daily dose, for $11, so between $0.20 and $8.50 / year.
            taurine powder: 277 g for $5, the highest excretion in WHO-CARDIAC was 270 mg/d (males of Beppu, Japan), so thats a 2.8 year supply, or $1.80 / year.
            I add these to a big pitcher of hibiscus tea brewing in the refrigerator, my main afternoon/evening beverage.
            iodine: essentially free if one uses iodized salt or eats seaweed regularly, otherwise 500 capsules sea kelp at 1.5 x RDA for $4.49, or $3.20 / year.

            Shop around. I’ve no complaints about PipingRock or VitaCost.

          • Adrien

            Thanks Darryl for all the details, I appreciate.

          • Dan

            Darryl, I am also curious where you are purchasing algal DHA at $100/year. The brand I am consuming, which is DHA supplement made by Flora and is 250 mg/d. costs me about $34 (with taxes) for a two-month supply. Thus a one-year supply would exceed $200, which I consider to be very expensive. I am interested to know if you know of another producer or company which sells “vegan” DHA for lower cost to the consumer.

            (The rest of my supplements – B12, kelp, D3 – are dirt cheap).

          • Darryl

            I haven’t bought any since a sale a year ago (though my freezer cache is running low). 365 day supplies start around $100, but that’s on sale. $150 is more realistic for online retail, and > $200 for brick-n-mortar retail. I’m brand agnostic, as nearly all of the brands (including Deva, Flora, Fuhrman, NuTru, Opti Spectrum, Ovega, Source Naturals) have sourced from Martek/DSM to date.

          • Darryl

            I’m agnostic on brand, as nearly all the vegan algal DHA brands (Deva, Flora, Fuhrman, Opti3, Ovega, NuTru, Spectrum, Source Naturals) have sourced from DSM to date. My freezer cache is running low, but I’ve spotted 365 x 500mg (DHA+EPA) of DSM’s in-house brand for $85. No endorsement implied.

          • Leslie

            Do you think that taurine supplementation is necessary on a vegan diet? Thanks for any thoughts on this.

          • Darryl

            I don’t know. I can say there’s evidence of lower taurine levels in vegetarians, numerous studies of potential benefits, no evidence of any adverse effects, and its rather inexpensive. It has a similar status to EPA/DHA: harmless, likely disease preventative, and lacking from vegan diets.

            With the exception of B12, we can produce all the “carninutrients” (B12, taurine, carnosine, creatine, carnitine and long-chain omega-3 fatty acids) ourselves, but perhaps not at levels optimal for resistance to chronic disease, ostopenia/frailty, or longevity. I’d love to see a supplement company produce a reasonably priced “carninutrient” pill to match omnivore intakes, so that vegans (and prospective vegans) could get the benificial components from omnivore diets, without the numerous deleterious ones.

          • Leslie

            Thank you. Yes, I find it interesting that as vegetarians we may not have optimal taurine levels. I try to maximize vegan protein foods to make up for this possibility but I am considering a supplement of taurine. My only concern is that taurine in supplements (from what i can tell) might not be from natural sources – thus, synthetics.

          • VegAtHeart

            Sorry to go a bit off topic, but I am interested in your claim that EPA/DHA is harmless. I assume that you are referring to the supplements. Have you come across any safety evaluations that convinced you so?

          • Darryl

            I don’t regard diminished synthesis from ALA as an adverse effect. Vegetarians can still markedly increase EPA/DHA via supplementation, and there have been no consistent adverse effects seen from LCPUFA supplementation. Personally, I’m not fond of the fishy burp, but its not bad if taken with meals.

            As to whether any positive effects are worth the expense, here are reviews of benefits seen in omnivores in primary & secondary prevention of cardiovascular disease, slowing cognitive decline, or treating depression. You’ll note that EPA (rather than DHA) appears the effective agent in some trials. This makes mechanistic sense given EPA competes with arachidonic acid (AA) for conversion to inflammation mediating eicosanoids, whereas DHA largely serves as a neural membrane component, important in child development, but maybe adequate in vegetarian diets for adults.

            Would any positive effects be smaller in vegans? Its difficult to say, vegans have lower incidence of cardiovascular disease, dementia and depression than omnivores. While consuming less less pro-inflammatory preformed AA, their plasma AA levels are about the same as omnivores. Its plausible that vegans who consciously consumed high ω-3:ω-6 ratio fats (flax, chia, canola oil) while avoiding high ω-6 foods (grapeseed, sunflower, corn, soybean & sesame oils, walnuts & pine nuts) might have much higher EPA:AA ratios without supplementation. On the other hand, they’d also shift the ratio more with smaller intakes of supplemental EPA.

            As far as I can tell, there are no studies of health outcomes with LCPUFA supplementation in vegans or vegetarians. A daily Ovega-3 starts at $93/year, I happen to consider it cheap insurance, but should high EPA/DHA transgenic flax come to market it would cost a small fraction as much.

        • doodeet

          A 10 year study was completed a few years ago where absolutely every fish known to man was tested for mercury. The world and it’s waste management programs have succeeded in contaminating every single fish known with mercury. No fish is “safe” to each. The smaller the fish and the shorter their life span, the less mercury. But there will be mercury in all.

  • guest

    Anecdote, My ex’s uncle used to fish in Lake Ontario until he developed dementia from mercury and heavy metal poisoning. He had to be hospitalized and have chelation for dangerously high blood levels. I don’t think any body of water is safe any more.

  • That’s a shame. So many moms are trying to do the right things (they think), and end up hurting their precious babies instead.

  • M85

    What i find really amazing is the amount of trolling that systematically goes on in the comments section here below….. is the favourite target for every kind of low carb/paleo troll.

  • Darryl

    The most extensive current survey of mercury levels in U.S. market seafood is this article, and don’t miss the full lists in its supplemental material.

  • Derrek

    Is Calcium Phosphate safe? I am looking to use caffein to lose a little weight and also for a little extra energy. I really have been going caffein free. Calcium (from Dibasic Calcium Phosphate)75 mg8%Caffeine

  • Red fox

    I am amazed that people who profess to follow Dr. Greger actually state that they doubt his integrity.

  • Richard Frazee

    All of this talk about Fish, Mercury and Unborn babies is good info, but how does this relate to us as adults. CAN we eat fish and which fish is best to eat and lastly, how much or that best fish can we eat? I for one love a nice slab of Cod now and then.

    • Thea

      Richard: There are plenty of good reasons/science behind *everyone*, including adults, skipping the fish (all meat really). Check out the following page if you want to do more research:

      Something to think about.

  • aklevach

    Fish from river, pond vs. Fish from ocean. Is there difference? Fish without polluted environment is good?

  • Paul Lundbohm

    An analytical method and results are given for the determination of total mercury residues in: Brussels sprouts; cabbages, heading broccoli and kale; potatoes; apples; carrots; imported tomatoes; tinned tomatoes, tomato juices and purees; rice; sugar. Residues in the 146 samples were in the range <0.001 to 0.010 parts/million, the mean being 0.0027 parts/million.

  • Paul Lundbohm

    The mean maternal hair total mercury level was 6.8 ppm and the mean child hair total mercury level at age 66 months was 6.5 ppm. No adverse outcomes at 66 months were associated with either prenatal or postnatal MeHg exposure.
    In the population studied, consumption of a diet high in ocean fish appears to pose no threat to developmental outcomes through 66 months of age.

  • alphaa10000

    Many of us routinely eat salmon, not tuna, because salmon has a higher level of EPA/DHA in its tissue than tuna and almost any other fish. Can you offer any data on the toxic burden of salmon tissue per ounce / gram, vs. other fish (including tuna)?

  • Anna

    Nothing is fit to eat anymore!

    • Thea

      Anna: SO MUCH is fit to eat today! When you eat a healthy diet of whole, unprocessed grains, legumes, veggies, fruit, nuts and seeds, you have incredible variety and taste all in a package that gives us great nutrition and best chances of avoiding the major diseases of our time.

      Here are Dr. Greger’s overall nutrition recommendations:

      If you are interested, I could give you some advice on where to get great recipe ideas/get started eating healthy.

  • Guest

    I wonder how incompetent you are? Corelation dont imply causation. Check maybe Japanese nation with highest fish consuption rates and why we dont see any problems there in brain imaging studies?.

  • Carmen Schwertner Stoffel

    Nota do médico

    Eu tenho mercúrio coberto de peixes antes em vídeos como Nervos de Mercury , Testing cabelo para Mercury antes de se considerar a gravidez , e Peixe Nevoeiro . Para saber mais sobre as conservas de atum, em particular, confira:

    Que marca de atum tem as mais Mercury?

    Cancerígeno Putrescine

    O Efeito de conservas de atum em salários futuros

    Amálgama recheios vs. conservas de atum

    Mercúrio em vacinas contra a Tuna

    O que mais podemos fazer para proteger nossos recém-nascidos? Vejo:

    DDT no sangue do cordão umbilical

    Como rapidamente pode desintoxicar Crianças de PCB?

    A maneira errada de Detox

    Diet Soda e nascimento prematuro

    Gases de carne: Dietary fumo passivo

    Mas o que sobre a longa cadeia ômega-3 DHA em peixes-não que necessário para o desenvolvimento saudável do cérebro? Esse é o tema