Doctor's Note

Still interested in mercury exposure? See my videos:
Mercury vs. Omega-3s for Brain Development
Hair Testing for Mercury Before Considering Pregnancy
Nerves of Mercury
How Long to Detox From Fish Before Pregnancy?
Fish Intake Associated With Brain40 Shrinkage
Which Brand of Tuna Has the Most Mercury?
Pollutants in Salmon and Our Own Fat

Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on mercury and tuna. Also, there are 1,449 other subjects covered in the rest of my videos--please feel free to explore them as well!

For more context, check out my associated blog posts: Mercury Testing Recommended Before Pregnancy and Tarragon Toxicity?

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  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other videos on mercury and tuna. Also, there are 1,449 other subjects covered in the rest of my videos–please feel free to explore them as well!

    • nicodemus2

      I recently found out that amalgam fillings in the teeth release mercury and I have about 4-5 of such fillings; should I remove them? Are there scientific articles encouraging it’s removal? I found this organization/video on the web touting for its removal because of it’s neurotoxicity:
      Are there risks of removing them?
      Thanks in anticipation of your response.

      • Kim Churchman

        Oh, many dentists would love to get their hands into your mouth! For a faaat fee!

    • PabloC

      Dear Dr. Greger:
      First of all, let me thank you for your excellent work here. It really helped me and I’m sure it will help others a LOT. I’ve been ovolactovegetarian since I was 4, and now I’m a vegan for almost 2 years.
      I’m also an odontology student, so I’m not only interested in nutrition but also in the subjects related to my career. I was told in the university that amalgam fillings release a minimal amount of mercury a day, so it’s not relevant as a health issue, ¿what do you think about it?. I would feel sorry about all the patients I put those grey fillings in if i knew they’re bad for health.
      Responding to those wondering if there is a risk removing amalgam fillings, yes there is: the risk that your dentist removes additional tooth material by expanding the cavity every time they remove it, either by iatrogenesis or because there is a caries under the filling. Another risk may occur because of the swallowing of the filling material, because of that, the dentist should always use a rubber dam before removing the amalgam fillings.

      • Kim Churchman

        And water spray, and high vac.

  • mjeejsmith

    I’ve read that Albacore tuna is bad but that chunk light tuna is safe and has safe levels of mercury (if there is such a thing). Is that true?

    • NickyC

      Hi Mjeejsmith,
      As we have learned, all types of tuna contain dangerous levels of mercury. This other video also shows the staggering levels of mercury in tuna: (

    • Toxins

      Hello mjeejsmith!
      Just to expand on NickyC’s comment, Nicky is correct. A safe level of a toxin should always be 0. Mercury is stored in fat and it can take years for you to actually remove the mercury from your body. Check out this video regarding fish contamination As with regarding the different types of tuna, check out the Environmental Defense fund’s website and they show the tunas with the lowest levels. But again, these levels of mercury are considered “moderate” and other contaminants are excluded. Especially when they say eat no more than 4 servings of US/Canadian albacore a month, you know there is something harmful just in that statement. Seafood now a days can be considered where the sewage winds up, they are almost always contaminated with a wide range of harmful chemicals, from PCB’s, Mercury and Dioxins to Arsenic. These chemicals are difficult to remove from ones system so we should not eat these foods as to avoid replenishing the supply of toxins in our body. Check out this video for more information on fish contamination

    • Kim Churchman

      There is always a safe level of every poison. Ever heard ‘the dose makes the poison’?

  • Lina Otalora

    Interested in the same previoos question about Albacore and chunk light tuna.

  • GabrielG

    I have lots of fillings in my teeth. Is there anything I can do apart from removing them?.

    I read that sardines are better than tuna regading mercury. Also, from the nutrition data I see they have more omega 3. What about mackerel?

  • DrDons

    Almost all fish are contaminated by mercury. So to minimized the ingestion of mercury it is best to avoid all fish. See I know of no credible sources recommending removal of fillings to reduce mercury load in the body. Omega 3’s are best consumed through natural sources (flax and walnuts) or by taking algae derived omega3’s(which is where the fish get it anyway)… see By avoiding fish you also avoid all the cholesterol, saturated fat plus all other contaminants such as PCB’s.

    • GabrielG

      Please not there are other countries apart from the US. Not all supplements are available everywhere.

  • nicodemus2

    Does anyone know a good place where you could go to test your mercury level- like doing a mercury hair test?

  • nicodemus2

    Dr. Greger,

    With regard to your video:

    I recently found out that amalgam fillings in the teeth release mercury and I have about 4-5 of such fillings; should I remove them? Are there scientific articles encouraging it’s removal? I found this organization/video on the web touting for its removal because of it’s neurotoxicity:
    Are there risks of removing them?

    I am confused because some people say that the exposure from amalgam is not sufficient to result in any health issues, and that taking out the fillings could cause more problems (i.e. weakening the tooth more, and increasing mercury exposure in the process).

    To further compound this case, the alternative to amalgam (composite resins/fillings) have also proven to be equally or even more toxic compared to amalgam. I have read several scientific articles and they seem to contradict one another.

    Thanks in anticipation of your response.

  • vetstud

    Dr. Greger,

    Thanks again for this incredibly informative website. I love it.

    A question: how did you come up with your calculation about how many mercury-containing dental fillings are equivalent to eating a can of tuna once a week?”

  • GabrielG

    Maybe instead of removing amalgams and cause problems it is better to take a supplement that captures the mercury. I read selenium is good but have no experience.

  • Didi Nour

    does this come from the TUNA or the CAN ?? what about ALL canned food? i didn’t find any video in this concern ???

    • Michael Greger M.D.

      That’s from the tuna itself, due to biomagnification up the food chain of the mercury largely released from burning coal.

  • Sara

    I’m not sure if this is still open as the last comment was a year ago but I will give it a go. I have to have a filling replaced and my dentist said the only option is a mercury amalgam filling due to the size and shape of the cavity. I am a nursing mother. Is it safe for me to have my tooth filled or should I wait? There is too much conflicting info out there. Thank you.

    • sf_jeff

      You can always get a second opinion.

    • Kim Churchman

      I can give a dental assistant/hygienist’s opinion. Switch dentists, or demand a ‘plastic’ filling, and if you promise that you’ll have the tooth crowned soon as you can, he/she will do it. It will be more fragile than amalgam, but not requiring that you chew on the other side unless you’re chewing something like jerky (why would anyone eat that anyway?). Apples, okay, beer nuts, no.

  • Gary Barnett

    According to the World Health Organization – Mercury is toxic to human health, posing a particular threat to the development of the child in utero and early in life. Mercury exists in various forms: elemental (or metallic); inorganic (e.g. mercuric chloride); and organic (e.g., methyl- and ethylmercury), which all have different toxic effects, including on the nervous, digestive and immune systems, and on lungs, kidneys, skin and eyes.

    Mercury is highly toxic, especially when metabolized into methyl mercury. It may be fatal if inhaled and harmful if absorbed through the skin. Around 80% of the inhaled mercury vapour is absorbed in the blood through the
    lungs. It may cause harmful effects to the nervous, digestive, respiratory, immune systems and to the kidneys, besides causing lung damage. Adverse health effects from mercury exposure can be: tremors, impaired vision and hearing, paralysis, insomnia, emotional instability, developmental deficits during fetal development, and attention deficit and developmental delays during childhood. Recent studies suggest that mercury may have no
    threshold below which some adverse effects do not occur.

    Dental amalgam is the most commonly used dental filling material. It is a mixture of mercury and a metal alloy. The normal composition is 45-55% mercury; approximately 30% silver and other metals such as copper, tin and
    zinc. In 1991, the World Health Organization confirmed that mercury contained in dental amalgam is the greatest source of mercury vapour in non-industrialized settings, exposing the concerned population to mercury
    levels significantly exceeding those set for food and for air.


  • Mercury Exposure

    Here is a much more detailed and nuanced breakdown of this comparision from the researcher who Dr. Greger quotes for his amalgma numbers.

  • Guest

    As this is a relevant topic, I was wondering?

    Root Canal Treatment? Its a dental procedure and even though there are surplus files and documents spilling around the Internet about faulty metal hips and metal teeth (such as above) Is there any real evidence linking Root Canal dental procedures with cancer? The idea about an abscess growing back in a dead tooth and mutating into something cancerous with no nerve sounds logical, but is there anything solid to note?

    • sf_jeff

      I would think that nerve damage is a lot more likely than cancer, but I wouldn’t rule cancer out. Especially if you are including “local” cancers, like you can get mouth cancers from chewing tobacco over the years.

  • barbarabrussels

    I don’t know if this guide is a reliable or biased source, but maybe it can add some nuance about mercury levels in different fish

  • TheLance3185 .

    End scene: James Bond and Jaws From Moonraker.

  • apprin

    Interesting to hear the opinions and research findings; however, I must consider one thing that no one has mentioned, according to my reading of these entries. When calculating “acceptable” and “dangerous” levels of the differing types of mercury, I hear people relating to tuna sandwiches and cancer rates. I haven’t heard anyone mention the presence of carcinogenic elements of enriched, processed flour and mayonnaise in the sandwich equation. Also, I haven’t heard anyone mention that cancer was virtually unknown before the “modern” age. Example: Several thousand mummies were autopsied to check for cancer presence in the non-modern or pre-modern age. Only one case of cancer was found – in thousands !! Now, we know that one in three to four people will be impacted by cancer. One in six men are already impacted by prostate cancer. At what level of exposure do we finally say, well, that’s acceptable to me?!?! We have made a fine art of processing, transporting and storing food. We experience a constant barrage of microwave and radio wave transmission penetrating our body, 24 hours per day, so that we can enjoy soap operas, satellite TV, cell phone and internet communication. We watch kids eating Skittles and popsicles without giving it a second thought. Cattle and chickens are fed concoctions that make them grow fast and infection free only as long as it takes to slaughter them, so we can cook them (and their man-made body chemistry) in oils from genetically modified corn and soybeans. At what point do we separate the fish mercury from the rest of life on modern Earth and define a formula to evaluate amalgam fillings?

  • rb99

    How do sardines fit into this picture?

    • Joseph Gonzales R.D.

      Hi rb99. Good question. I think sardines would have lower mercury levels than tuna (most other fish do) since they just eat plankton. They still have mercury from what i gather, but I am unsure exact amounts. It appears contaminates can vary based on location and type of fish. A study from the U.S. shows doses of lead, cadmium and arsenic in canned sardines. This study in Port Moresby tested different levels of fish and found sardines to be the lowest. I am not sure any level of mercury is safe. Some other videos that mention sardines and if interested, here and here. One video is on atrial fibrillation, the other on
      amnesic seafood poisoning.

  • 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 the cognitive tests?.

    • Joseph Gonzales R.D.

      Please no name calling on the site. This video is about canned tuna and fillings not Japanese populations and cognition. Thanks.

  • Noe Marcial

    i have to say that i don’t agree with the conclusion sugent in the present video. as Michael says, it is not a good thing compare something with the worth things.. if fish is worst doesn’t mean amalgam is safe! (it is not said but sugent) the other day an amalgam have break to my aunt during night, she have swallowed part of it without notices. amalgam breaks.. and its relatively common..