Doctor's Note

Mercury vs. Omega-3s for Brain Development is the study about balancing risks and benefits.

I explored how long it takes to get rid of some of the other pollutants in How Fast Can Children Detoxify from PCBs? PCBS are found most concentrated in fish and eggs (Food Sources of PCB Chemical Pollutants), which may be why there are lower levels of Industrial Pollutants in Vegans. This may also help explain the remarkable findings in Eggs and Diabetes.

The fact that we can still find DDT in Umbilical Cord Blood decades after the pesticide was banned speaks to the persistence of some pollutants. There’s a shortcut for moms, but it’s The Wrong Way to Detox.

More on the risks of mercury can be found in these videos:

For more context check out my blog: Top 10 Most Popular Videos from 2013

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  • DH

    Off topic (considerably), but does anyone know if horseradish containing “artificial oil of mustard” is bad for you?

    • The Material Safety Data Sheet on synthetic mustard oil can be found here:

      If you celebrate, Merry Christmas!

      • pmh

        Deigning to respond to irrelevant questions while some really pertinent ones go unanswered is rude. Get some manners, or I’m going to have to stop coming to the website to watch or read you. (I’ll just watch when you happen to show up in my youtube recommendations.) I don’t do “uncomfortable” for anyone, and your arbitrary and capricious responses are irritating. Bottom line: Either respond to everyone or no one. (And “Happy Holidays” fits everyone.) Happy Holidays!

        • Toxins

          PMH, there is a team of nutritionfacts volunteers (like myself) who can address questions you may have. It is impossible to address every question, and at one point early on in nutritionfacts Dr. Greger did do this. The popularity of the site has grown beyond what Dr. Greger can handle. Remember, is not his job, it is his side “hobby” done purely without profit and we should be grateful he has done this for the public good.

          • pmh

            Thanks for the civil response. I guess I haven’t been around long enough to have seen enough “volunteer” responses to notice your existence. All I’ve seen is video introductions by Gregor with entreaties to ask questions (to which I see plenty of responses with no answers). “Public good” is one thing, but so is the simple courtesy of answering questions you asked for. I don’t see that language in this post. Perhaps what I’m seeing is early posts that include out-of-date sentiment of pure solicitation (i.e., “please make me look successful by asking me questions!”). One can only hope.

          • Toxins

            You will notice that every so often Dr. Greger will dig deep and answer a question in depth in the link below.

          • pmh

            That link is helpful. I guess the true source of my irritation is having Dr. Greger introduce something really pertinent to my personal interests, have people bring up questions in the comments I’d also like answers to, and then – nothing. I see several “in depth” treatment of issues I might find answers or insight into in that link. Thanks!

          • rueka anderson

            You are certainly demanding.

          • Penny

            and you are irrelevant.

          • rueka anderson

            Irrelevant is your view that the world revolves around you.

          • rueka anderson

            He has other hats to wear.

          • VegAtHeart

            Fair enough about time constraints that limit the number of comments that Dr. Greger can directly respond to, but I would at least like to see in-depth responses to all comments and questions that legitimately challenge the accuracy of content provided by Dr. Greger’s videos.

            Dr. Greger has assumed the responsibility of being a messenger of the science of nutrition to the general public. Therefore, he should also be prepared to defend the accuracy of what he says and, where warranted, seek more information and provide clarification.

            As a recent example, I would like to see an acknowledgement and response to this recent thoughtful challenge by Darryl to Dr. Greger’s description of the mechanism by which nutritional antioxidants provide health benefits.

          • pmh

            You’ve expressed the precise logic behind the impetus of my original comment, albeit with slightly (that’s a joke) more restraint. Thank you!
            I apologize to you and anyone I offended by my less than PC bluntness. As I get sicker, time grows shorter and more precious. Nowadays my ability to tolerate even the smallest trifle is (I see) non-existent.

        • zapp7

          You’re the one in need of manners…

          • pmh

            Doubt you would know a grace if one bit you in the butt.

        • Richard

          Merry Christmas, Merry Christmas….And a Happy New Year….Too bad if you do not like it!

          • rueka anderson

            Filtering system, please. It is too time consuming to have to sift through rantings.

          • MzKozi

            Just curious, when one says “Happy Holidays” what holidays of what kind are they referring to? If it suits everyone, – then everyone has the same kind of holidays – but from what? Why are there holidays ?
            Just curious ….

        • Thea

          pmh: Personally, I really appreciate that Dr. Greger responds when he can. I don’t consider it rude at all that he doesn’t respond to every question, especially when so many of the questions have already been answered. I would rather Dr. Greger spend his time on producing new content for this site.

          As for your, Happy Holidays, it is a myth that it applies to everyone. If you wish to be respectful of your fellow humans, you will be careful how you use it.

          • Eve

            For example, Jehovah Witnesses do no such celebrations.

          • rueka anderson


        • Christo Okulian

          pmh: am so sorry, but by seeing your respond above. i know the issue is not in Dr. Greger and not from the NF team whose both i respect. they did good enough for whatever the can contribute in this area. you are not the only one that rarely be answered by Dr. Greger and by the team, me too, i ask many times but many times unanswered.. still i am okay with that. so be secure for your self whenever you find your question or someone’s question hasnt been answered for long. bottom line: the issue is on you including your happy holidays issue, u really need to check your “heart”, dont sweat such things. u wont get sick by such words.

          • pmh

            You should consider spending more time minding your own psychological and emotional health, and less on projecting your own illnesses onto the hearts and minds of perfect strangers.

          • Lloyd

            Irony of the century.

          • pmh

            The civil part of this conversation ended 4 days ago. Learn to read – or in your case – when to stop.

          • Birtee

            This saddening to some of us. Please let it end. Many of us have much greater life stress. Please don’t add to it here.

          • pmh

            Then stop contributing to it! Do you have a greater life stresser than end-stage progressive multiple sclerosis for which the only hope I now have of reclaiming some resemblance of a functional life after 30 years of failed traditional medicine is in some complex nutritional key to nerve regeneration hidden within the answers to some of these questions? Really people, I don’t give a fig about your opinion of my comment. You bring on your own stress by dwelling on stupid things. Get the bleep over it!

  • A

    Is it true that selenium binds with mercury and eliminates it out of the body? For those of us NOT trying to get pregnant but still having a few amalgam fillings, would it be helpful to eat 1-2 brazil nuts a day to eliminate the mercury out of our bodies faster?

    • Catherine J Frompovich

      In the Christmas spirit, may I offer this about mercury (Hg) and amalgam fillings. As long as a person has ‘silver fillings’, i.e., amalgams, in one’s mouth, mercury is still releasing and no amount of Brazil nuts a day would eliminate the mercury since the source is still emitting Hg. Assays on amalgams removed indicate that Hg releases from amalgam fillings over the time they are in the mouth. The indicator of that fact is this: Amalgam fillings are 50% Hg and 50% what’s called a eutectic mixture consisting of copper, tin, silver, and zinc, so there should be 50% Hg in the removed filling. Assays have indicated Hg content down from 50% to between 24 and 26%. The missing Hg either vaporizes or is abraded by chewing action.
      Many European countries long ago banned the use of mercury in dental fillings.
      The better part of discretion, I think, would be to have the amalgam fillings removed CORRECTLY by a dentist who is familiar with the proper procedure/protocol, and go on a detox program with proper supervision. Then you will be able to eliminate much of the mercury, if you don’t eat tuna, swordfish, mackerel and seafood, i.e., crustaceans, which are bottom dwellers that are subject to more pollutants.

  • John

    The video audio was 10% of the norm and impossible to hear. Is it possible to re-do re-issue, perhaps. The data is outstanding, helpful and invaluable. Pls continue. Merry Christmas to you as well!.

    • Richard

      Nothing wrong with the video, check your equipment…

  • DH

    Dr Greger,
    What is a good way to stay cognitively intact as we age, other than eating a plant-based diet? Are there specific foods you recommend (e.g. cocoa) that help to save off mild cognitive impairment and gradual cognitive decline?
    Many thanks and a fan of yours,

    • HemoDynamic, M.D.

      This is a very in-depth question. So the best way to get the answer to your questions is to use the search engine on this website.

      Here is the search I did for Cognitive Decline:

    • HemoDynamic, M.D.

      That is a very in-depth question. So the best way to get information to you inquiry is to use the search engine on this website.

      Here are the search results for Cognitive Decline:

    • Thea

      DH: I recommend Dr. Barnard’s book, “Power Foods For The Brain – An Effective 3-Step Plan to Protect Your Mind and Strengthen Your Memory” He also has a companion video, with less info, that is well done and perhaps worth sharing with trusted patients: “As seen on public TV: Protect Your Memory”

      • HemoDynamic, M.D.

        Yes this is also a good resource as well with lots of very helpful and useful info. thanks Thea! I hope you had a Good Christmas (If you celebrate it).

        • Thea

          Dr. HemoDynamic: Thanks for your nice note!

          I don’t happen to celebrate Christmas, but I appreciate your qualification and your well-wishes. I also have well-wishes for you! If you are in part of the world experiencing extreme cold, I also hope you are staying nice and warm. Take care.

    • Merio

      i think that the best way to protect the “mind” is to use it!! :-)
      Apart from the correct nutrition; logic/math games, meditation and having different kind of interests keep the mind smart and ready to learn something new everyday… IMHO obviously… even music could plays an important role in this issue…

    • rueka anderson

      Since I did not see an answer from the doc. How ’bout excersize and Lumosity. Sorry about my spelling and budding in.

  • Ronald Chavin

    Here are 7 scientific studies that indicate that fish eaters are not more likely to develop diabetes compared to people who don’t eat fish, thereby contradicting the 1 scientific study that Dr. Greger shared with us:

    Conclusion: Eating fish without any salt added will greatly lower our risk of developing cardiovascular diseases, stroke, all cancers, brain diseases, bone diseases, kidney diseases, any many other killer diseases without increasing our risk of developing diabetes. Because diabetics frequently die of cardiovascular causes, diabetics who eat fish (or swallow fish oil softgels) will live much longer than diabetics who become deficient in marine omega-3s.

    • Ronald Chavin

      According to the following scientific study, the people who ate too much white rice had a higher risk of developing type 2 diabetes:
      In this same study, the people who ate brown rice or other whole grains had a lower risk of developing type 2 diabetes.

      My hypothesis: People who eat fish tend to eat more white rice than people who don’t eat fish. Therefore, white rice consumption should be made an important confounding factor in all scientific studies that try to connect fish consumption with diabetes risk.

      In other words, people who always eat fish without white rice would have a very low risk of developing type 2 diabetes but people who always eat fish with plenty of white rice would have a very high risk of developing type 2 diabetes.

    • Daniel

      Most of those studies you linked are not relevant to your take on Dr.Gregers video.

      “Fish-seafood consumption, obesity, and risk of type 2 diabetes: an ecological study”, It states that “The results of this study suggest that high fish and seafood intake may reduce the risk of type 2 diabetes in populations with a high prevalence of obesity”,
      so sick people might get less sick if they adhere to a diet that has more fish and seafood. I bet there are other confounding factors to this

      “Effect of omega-3 fish oil on cardiovascular risk in diabetes”,
      does not say anything about favorable outcome of the diabetes itself. It states that due to its ability to inhibit platelet aggregation it may reduce cardiovascular risk.

      “Fish oil improves arterial compliance in non-insulin-dependent diabetes mellitus”,
      Is a study based on fish oil, not fish consumption

      “A controlled study on the effects of n-3 fatty acids on lipid and glucose metabolism in non-insulin-dependent diabetic patients”,
      again, a study on fish oil, not fish consumption.

      “Diabetes and impaired glucose tolerance among the inuit population of Greenland”,
      again, this was the summary” whereas frequent intake of fresh fruit and seal meat were inversely associated with diabetic status”, can it be the fruit?

      “Fish-seafood consumption, obesity, and risk of type 2 diabetes: an ecological study” “Results from this meta-analysis indicate differences between geographical regions in observed associations of fish consumption and dietary intake of long-chain n-3 fatty acids with risk of type 2 diabetes”,
      so both yes and no.

      “Combination of conjugated linoleic acid with fish oil prevents age-associated bone marrow adiposity in C57Bl/6J mice”,
      the title says it all, CLA and fish oil in mice. So no fish, again its oil in combination with CLA and its in mice

      I would ask that at least half of the listed studies and reviews were relevant.

  • HereHere

    I’ve just read the transcript and the questions below. However, what I know about mercury is that is passes through the blood brain barrier (BBB). Too much causes Minimata disease (aka Mad Hatter’s disease), somehow interfering or damaging brain cells. So even though Mercury has a 2 month half-life in hair samples and blood, how do we know it isn’t accumulating in the brain? I suppose that once it passes through the BBB, it could pass out of the brain as well, but does anyone have any knowledge about this? My previous understanding was that mercury was bioaccumulative. Thanks!

  • Reuven Rosenberg

    It’s so frustrating that even the “healthy” foods are now dangerous.

    • Thea

      Reuven: Happily, the real healthy foods are plentiful. Eat whole foods in these categories: fruits, vegetables, whole grains, legumes, nuts and seeds. Wash them down with teas like green and hibiscus. All of those foods, in general, always have been and (based on our current knowledge) likely always will be healthy.

      It is only those questionable foods, like fish, which have been falsely promoted as healthy due to history and politics that appear to be switching sides. I completely understand the frustration. I just think it is worth putting into perspective.

      Good luck!

  • Carter

    I am a graduate student who will be attending medical school next fall. I am required to re-immunize for hep B after showing no resistance to it from the titter. I was hoping you would be able to provide options for the safest vaccines out there, not only for myself but for my children as well. Any help would be greatly appreciated.

  • Usc

    Does this imply that women should loose weight before pregnancy to prevent pollutants stored in their fat cells from releasing PCBs?

  • Nickolas

    so stay away from vaccines due to mercury?

    • Robert Haile

      Tell that to my medical partner who was raised in Pakistan, was prevented from having the Polio vaccine and is a quadriplegic for life. A tuna steak carries far greater mercury than any vaccine.

  • Nickolas

    They also contain bovine serum is that worth the risk too?

  • Bethany

    I’m studying for an exam tomorrow on pregnancy nutrition as part of an
    RD program and I’m supposed to be recommending 1-3 meals of
    bottom-feeder fish every week for fetal development. I saw the video and am now very curious.

    Are you saying that the mercury levels in most fish, if eaten once a week during pregnancy, are worse for infant health than the exposure of mercury over 6 vaccine injections?

    Based on the title (and the title versus the information within the video), I wanted to make sure I understood your point correctly. Thank you!

    • Joseph Gonzales R.D.

      Hi Bethany, are you still interested in a response? How did the RD exam go?! Best wishes let me know if you are still interested.

      • Srivani

        Hi Joseph,
        I would like to know your response. I posed a similar question to Dr. Greger today?

        • Joseph Gonzales R.D.

          I am not sure if it’s worse for infant health. The study highlighted was just looking at how much mercury an infant may accumulate from breast milk in mother’s who ate fish vs. how much mercury infants accumulated from mercury-containing vaccines. The full study can be found in sources cited. I think the point is that mercury from mothers milk is similar in concentration to that of vaccinations, based on that study.

  • Youcef

    Off-topic as well, slightly only though. Newborns have immune tolerance for a period that goes from up to about 6 to 18 months. Shouldn’t we wait for babies to finish their period of immune tolerance before exposing them to ANY vaccines? Because if these babies were to recognize a virus as part of the “normal” environnent they need to be ready to take part in wouldn’t a vaccine end up doing the very opposite from what’s it’s supposed to do?

    • Joseph Gonzales R.D.

      My Uncle is Pediatrician he says it makes no sense to wait on vaccines, as the really bad diseases affect infants, and young children the most. Pertussis, Meningitis, etc. All preventable with minuscule risk. This is a chart from the CDC on a vaccine timeline.

      • Youcef

        1) I do not doubt that your uncle said that. In fact many pediatricians say that. My question isn’t so much what does the medical body say, I know what they say. I am more interested in question what seems like a dogma ignoring fundamental biological data. A) My question to you is do you of a period of immune tolerance at birth? B) Does you uncle know? It’s in medical textbooks in France, in fact it’s in high-school textbooks too in France and it seems like there is little doubt of about that being a fact. That’s the plane I’m interested in debating on, observed biological facts.
        C) Do you or not have the knowledge or the proof of the opposite that when a baby is born, it comes to the world inheriting its mother immune system, which slowly fades out as the child develops its own?
        D) Finally, after you check the above facts, and are able to confirm them or infirm them on biological grounds, I ask: why would a child from a vaccined mother receive a vaccine during a period where 1) he/she doesn’t need it since the mother’s vaccined immune system is inherited 2) he/she is at risk of recognizing the virus as part of the normal/tolerated environment of the body.
        Appendix 1: The entire hygiene theory related to the prevention of asthma / allergies is based on exposing children to the natural environment during the period of immune tolerance.
        Appendix 2: If you’ve heard of neonatal graft requiring no need for later immune suppressants (done in humans as well) it is based the same neonatal immune tolerance.
        2) On “miniscule risk”. Is it your impression or a fact. You seem to present it like a fact. Would you say for certain that early vaccines have no link with much later degenerative disease?

        Note on form and intention: There is no personal challenge here although reading the text only without the man it may seem like it I reckon. I invite you, in a friendly manner and certainly intention to look into biological fundamentals, nothing more. If I am wrong on certain points I’ve always welcomed people to show me so, all I require is a scientific process and a genuine intention to establish the truth rather than a point. There’s nothing I invite more vividly than an opportunity to upgrade my paradigm of the truth.

  • Robert Haile

    A few years ago, it took me 4 months to get my toxic level of mercury at 38 to 6, my last bastion of any animal meat. All animals concentrate the toxic dumping of pollutants + the ones they are deliberately fed. Guess in this area I was a slow learner. Maybe it was the mercury?

  • Raja Blanco

    Is Salmon very high in Mercury. And what are the main seafood with high Mercury exposure.
    Thank you