Dr. Oz takes a big bite of bad science

Mehmet Oz hosts a popular TV show that reaches millions of people.  He offers a constant stream of medical advice, and he is popular because he makes his topics sound dramatic, or exciting, or surprising, or all three.

Unfortunately, Dr. Oz sometimes has a poor understanding of science.  At least I hope so, because he promotes so many outrageous treatments, with such enthusiasm, that the only other explanation I can think of is that he is simply a fraud. I don't think that's true, so let's give him the benefit of the doubt and assume that when he makes a mistake, he is simply ignorant of the truth.  His latest startling revelation is that the metal fillings in your teeth are very, very bad for you.  Or are they?

Last week, Dr. Oz hosted a show called "Toxic Teeth: Are Mercury Fillings Making you Sick?  The show looked at silver amalgam fillings, which contain a small amount of mercury chemically bound within them.  Mercury is indeed a toxin.  Should you worry?  

One problem with taking a skeptical look at a Dr. Oz show is that he packs each episode with scientific claims, coming at you thick and fast, and it would take hours to critique them all.  Instead, I'll just pick a few, which illustrate Oz's lack of concern for accuracy, and his apparent ignorance of the underlying science about dental fillings.

Dr. Oz opens his show with a dramatic claim about mercury: 
"This thermometer contains mercury," he says, holding up a very small thermometer. "If I were to drop it, we would have to evacuate this entire studio immediately!" 
Now, this is complete nonsense.  If you drop a mercury thermometer, you should carefully clean up the mercury, which beads up into nice little silver-colored balls.  No one in the room is in danger, unless perhaps they try to drink it.*

This opening salvo should set off anyone's skeptical alarm bells.  Here's a guy who doesn't seem to mind exaggerating to make a point.  Why trust anything he says in the rest of the show?  I suspect, though, that after watching this episode, thousands of Oz's loyal viewers raced to the phone and made appointments to have the silver fillings in their teeth removed.

Dr. Oz continues his introduction by explaining that mercury is contained in silver tooth fillings.  No one knew, he claims, that mercury vapor could be released from these fillings, but this news:
"sparked a firestorm 30 years ago [here the show cuts to a graphic of a fireball exploding] when major news reports brought to light the potential TOXICITY of mercury fillings.  ... Now there's mounting new evidence showing mercury is released when you eat, and even when you brush your teeth."
Quick, run to the dentist!  Get this toxic mess out of my mouth!  

But hang on a minute.  Why aren't people dropping like flies from the fillings in their teeth?  With little effort, I determined that, contrary to Dr. Oz's statements, nothing new has been discovered lately about silver tooth fillings.  I found studies going back to the 1970s that shown that we've long known for decades that mercury is released from these fillings. But Oz ignores all these.  He even announces, a few minutes into the show, that 
"for the first time ever, I'm going to show you what happens when you brush your teeth with mercury fillings."  
No, this is not the "first time ever."  As a scientist, I find it worrisome that Oz seems quite comfortable claiming, incorrectly, that he's the first person ever to tell the world about this.

Perhaps the most outrageous - and unintentionally funny - segment of the show is the "demonstration," where Oz introduces an Oz-certified expert on mercury vapor, David Wentz, who has a gizmo that looks like it was built by a sideshow huckster.  The device is a plexiglass box that looks like it was meant to handle biohazards, with black rubber gloves that let you manipulate its contents.  In the box: a set of fake teeth containing... silver fillings!  And a toothbrush!  

As he walks over to the device, Oz says "I work with Dave Wentz and his Ph.D. dad."  This goes by really fast, so you would be excused for not realizing that Dave Wentz himself doesn't have a Ph.D., and for not knowing whether he has any credentials at all.  Dr. Oz conveniently omits the fact that Wentz and his father run a highly profitable nutritional supplements company, USANA http://www.usana.com/dotCom/about/index, which happens also to donate money to Oz's nonprofit corporation, HealthCorps.  Hmm.

Dr. Oz then reaches into the box, and while the audience watches in hushed excitement, he brushes the teeth, right on top of those silver fillings!  Right on cue, Wentz proclaims that the mercury vapor reading hits 61 in just a few seconds. 
"Anything over zero is toxic," Wentz proclaims.  "And we're at 61."
"Oh my goodness, 61!" Dr. Oz exclaims.
"That mercury is coming off the fillings, into your mouth, going across the blood-brain barrier, into your brain," says Wentz dramatically.
Wow.  I've been brushing my teeth (which have several fillings) for years.  How can I not be dead?

As Dr. Oz should know, "the dose makes the poison."  Even water can kill you if you drink too much of it.   Wentz is clearly wrong to say that "anything over zero is toxic."  

How much mercury is safe, then?  

According to the EPA, 0.1 micrograms of mercury per kilogram of body weight per day is safe.  For an adult who weighs around 150 pounds, that's about 7 micrograms.  A 6-ounce can of tuna has about 20 micrograms of mercury, about 3 times the safe amount per day.  Scientists do have real concerns that mercury in tuna and other fatty fish might present a health hazard.   

Dr. Oz's device seemed to show that 61 micrograms of mercury were released from brushing teeth, which would be about 9 times the exposure that is considered safe.  Is there really a risk here?

Well, no.  The EPA has found that "nearly all methylmercury exposures in the U.S. occur through eating fish and shellfish."  (Admittedly, though, this is not mercury vapor.) The precise question that Oz claims to be explaining "for the first time" has been examined in multiple studies, and the evidence is that silver fillings are harmless.  (See the FDA summary here.)  

A thorough scientific review in 2004 concluded that:
"The current data are insufficient to support an association between mercury release from dental amalgam and the various complaints that have been attributed to this restoration material. ... Individuals with dental amalgam-attributed complaints had neither elevated HgU nor increased prevalence of hypersensitivity to dental amalgam or mercury when compared with controls. The findings of these studies suggested that individuals with complaints self-attributed to dental amalgam should be screened for underlying dental, physical, and psychiatric conditions."
So no, there's no evidence that mercury from silver fillings causes any health problems.  None.

But what about that device on Dr. Oz's show, which showed 61 micrograms being released in just a few seconds of brushing the teeth?  My conclusion is that the device in Dr. Oz's studio was either wildly inaccurate or simply fraudulent.  The setup was almost a parody of what real scientific instruments look like, and nothing about it gave me any confidence that it was reliable.  I would suggest to Oz that before making a claim like this, he should ask rigorously trained scientists to make the measurements using properly calibrated equipment.  A TV studio is no substitute for a real lab. 

But wait: Mehmet Oz is a Professor of Surgery at Columbia University - he must know his science!  Plus he has an M.D. from the University of Pennsylvania, and he did his undergrad studies at Harvard.  By all appearances, he is a very smart guy.  If his show were about heart surgery - his specialty - it would no doubt be professional, accurate, and probably far too technical to attract an audience.

Here's the rub: despite his credentials, Oz is not an expert on mercury amalgam fillings.  He probably could have read and understood the science, but he appears to be unaware, or too busy to  be bothered by, the many scientific studies on this subject. Had he done his homework, he might not have presented such a spectacularly overblown episode that seems intended to scare people into removing the silver fillings from their teeth.  

So there's no need to go out and get your silver fillings replaced.  It's too bad that a highly educated surgeon like Mehmet Oz, with such a big audience, prefers to present wild exaggerations rather than telling people the truth.  Perhaps, though, the truth just isn't that exciting.

*Note added on followup: Even swallowing is rarely harmful.  From J. Dodes: "Acute toxic exposures to  elemental mercury are rare but there have been cases of elemental mercury being accidentally released directly into the  bloodstream from broken rectal thermometers and when elemental mercury had been swallowed intentionally in an attempt at suicide.  In all these cases there was no long-term effects from the mercury."  Dodes, JE.  The Amalgam Controversy:an evidence-based analysis.  JADA, 132:348-56, 2001.


  1. <>

    Mercury vaporises are room temperature. So yes, people would be in danger.

  2. Re: "Is there really a risk here? Well, no. The EPA has found that "nearly all methylmercury exposures in the U.S. occur through eating fish and shellfish." Silver tooth fillings contribute only a neglible amount."

    Quantities of mercury are measurable in totally different forms of mercury, with different sources and also different reference ranges. The main type of mercury emission being measured from the fillings is the mercury vapor form, not the methylmercury form. Therefore the EPA comment about methylmercury is not a correct comparison and simply does not entail your conclusion that there is therefore no risk.

    In saying so, you commit two of the common errors of fallacy: hasty generalization (the fallacy of inferring from some to all) and ad ignorantium (the fallacy of supposing lack of proof proves something). This is also an example of the syndrome you cite in your opening: the statement is either made in ignorance or fraudulently, but either way, is misleadingly false.

    1. Good point - I edited the post to clarify this distinction. Still, my main points about Oz remain valid.

  3. Your primary reference for your primary claim is "A thorough scientific review in 2004". I see that this review was only "thorough" for studies published between 1996 and 2003.

    As you rightly said yourself, "I found studies going back to the 1970s..." Ah........ yes. Therein lies the rub. A great deal of research has indeed been published on this subject, over a long period, but when the International Academy of Oral Medicine and Toxicology (IAOMT) began funding independent research of a higher quality, especially in the 1980s and early 1990s, the findings were overwhelmingly concerning.

    So much so, that a number of governments around the world legislated against the use of mercury dental fillings at that time - leading to the complete withdrawal of their use - such as, for example, Switzerland, Norway and Sweden.

    Are you therefore saying that the governments of countries such as these acted based only on speculative pseudoscience? In fact, the explanation is simple: they did more research than you have done, a statement I make based on the poor treatment of this subject in your article above, which shows a poor knowledge base.

    A second fruitful period of research was the last decade - i.e., SINCE 2003 - which has led to the UN Environment Programme issuing a recommendation to phase out all uses of mercury INCLUDING dental fillings because of environmental hazard - another major aspect of the topic you do not even refer to in your article.

    How convenient, then, that the only reference you give limits itself to a small number of years within your definition of "thorough", 1996-2003, which also happens to exclude two of the most fruitful periods of research on this topic. And, I say this even assuming (which is a very big assumption, that may prove incorrect) that the review you cite was well done.

    For better, more comprehensive science on this subject, and quality references and articles, I would suggest instead that any reader see http://www.iaomt.com/category/articles.

    1. Actually, for a more comprehensive debunking, see Stephen Barrett's lengthy discussion, http://www.quackwatch.org/01QuackeryRelatedTopics/mercury.html or the entire site he created for dental quackery, http://dentalwatch.org/.

    2. More comprehensive ? Really ? Your response indicates you did not bother reading anything at the link "commenter "biggies" gave you.

      As a "scientist" it should concern you that they were huge errors in the FDA's amalgam rule. Luckily the IAOMT and other scientists pointed out the FDA mistakes in their "petition for reconsideration". This petition prompted FDA to take another look at the amalgam issue in 2010. FDA (and HHS) is sitting on the amalgam rule, so IAOMT has sent in an addendum to the FDA on the new science that has been published in the last 2 years. You can read about it here or watch a video with IAOMT attorney discussing it.


    3. BIGGIES, that was known as the LSRO scandal. That is where FDA circumvented the competitive bidding laws so they could get LSRO to do the review.

      Here is a video of lawyer who uncovered this through FOIA documents.

      Additional problems with the contract / review

      -- Issue #1: Did NIDCR officials Lawrence Tabak, Norman Braveman, and Marion Blevins attempt to circumvent the competitive bidding laws?

      -- Issue #2: Did Tabak, Braveman, and Blevins generally engage in activities designed to cover up their violations by creating a façade of legality?

      -- Issue #3: Did Tabak, Braveman, and FDA’s Runner put together an “outcome biased” study?

      -- Issue #4: Did Director Tabak provide false or deceptive testimony to Congress about the LSRO/BETAH deal?

      -- Issue #5: Did NIDCR take over what was really an FDA project?

      -- Issue #6: Did Braveman – along with Runner, “subcontractor” LSRO, and “contractor” BETAH – shut interested citizens and consumer groups out of the process, despite assurances to the contrary?

      -- Issue #7: Did BETAH willingly accept its role as the strawperson contractor, in light of its lack of expertise to do scientific studies, or was it pressured into going along with the scheme out of fear of losing other NIH business?

      -- Issue #8: Did the participants misrepresent the contract as a “conference” instead of a “study”?

      -- Issue #9: Did LSRO secretly negotiate a contract, even though it was neither an existing contractor, nor a sole source supplier, nor the winner of a competitive bid?

      -- Issue #10: Did LSRO conduct an “independent” scientific inquiry?

      for more information on this scandal, go to the link above.

  4. Posted at Forbes, but thought it should be here as well. Steve, you do yourself and your “skeptic” readers a disservice by offering so many flagrant inaccuracies.

    How odd that you seem unaware that mercury vapor as released from amalgam fillings is extremely toxic (10x more toxic than methylmercury if using the EPA’s RfC’s for comparison). Of course as a “scientist” Salsberg knows being exposed to mercury vapor doesn’t immediately kill someone, he uses that benchmark out of ignorance or to intentionally mislead people as anyone who has browsed the scientific literature knows exposure to mercury vapor induces a multitude of symptoms depending upon the person, not immediate death as you like to infer.

    Through-out this article, Steve is not one for details when it get’s in the way of his misleading statements. Had he bothered to look he would have found that mercury spills (as from a thermometer or other sources) are a very big deal at least to the EPA and ATSDR (Video of PSA from EPA / ATSDR below).



    I had to laugh at your statement that there was no recent evidence to suggest mercury fillings are unsafe. One would expect that you would at least do a search of the scientific literature before writing such an bold (inaccurate) statement. List of a few recent studies are at the bottom of message.

    Additionally you incorrectly tried to link methylmercury as the main source of mercury from dental amalgams. This oversight is so outrageous that I find it humorous that you would write it. As you like to try and frame things… "either he is ignorant, or a fraud !"

    You could easily have quoted, the only USA risk assessment on amalgam (based off CDC’s) NHANES dataset, which was done in cooperation with the FDA ( Richardson, G.M., Mercury exposure and risks from dental amalgam in the US population, post-2000, Science of the Total Environment, 409 (2011) 4257–4268))

    - this study found that using the 20 year old EPA RfC, over 60 million Americans receive more than what is considered “safe” from their mercury fillings. If a more up to date RfC was used (such as CAL-EPA) then all 120+ million American with amalgam would be over the daily “safe” limit. Once again, for those who’ve read Steve’s article, that is MERCURY VAPOR, not methylmercury.

    REFERENCES, from the IAOMT petition to the FDA

    Recent published studies (discussed below) revisiting the CAT data have largely rebutted and disproven the conclusions of the CAT parent studies, demonstrating that adverse effects in these children are identifiable and dose-dependent. Moreover, authors of these parent studies have recently published an additional study demonstrating that the subjects of those studies demonstrated neurobehavioral harm as a result of the placement of mercury fillings.

    Woods, J.S., et al., Modification of neurobehavioral effects of mercury by a genetic polymorphism of coproporphyrinogen oxidase in children, Neurotoxicology and Teratology 34 (2012) 513–521),

    Geier, et al., A dose-dependent relationship between mercury exposure from dental amalgams and urinary mercury levels: a further assessment of the Casa Pia Children’s Dental Amalgam, Trial Hum Exp Toxicol. 2012 Jan; 31(1):11-7)

    Geier et al. A significant relationship between mercury exposure from dental amalgams and urinary porphyrins: a further assessment of the Casa Pia children’s dental amalgams trial, Biometals (2011) 24:215-224)

    Al-Saleh, et al., Mercury (Hg) burden in children: The impact of dental amalgam, Science of the Total Environment 409 (2011) 3003-3015)

    Mutter, J., et al., Does inorganic mercury play a role in Alzheimer’s disease? A systematic review and an integrated molecular mechanism. (2010)

    BTW: By sending the previous commenter to quackwatch, that tells me you are not one for intellectual curiosity when it comes to learning about something which you think you know something about.

    1. Elemental mercury 10x as toxic as methylmercury? I'm afraid that you have those reversed there. Methylmercury is substantially more toxic than is elemental mercury. Perhaps " the EPA’s RfC’s" aren't as good indicators of the toxicity of materials as, well... the toxicology of those materials.

    2. I see, so instead of relying upon EPA's established RfC's for a reference I should rely on your opinion that methylmercury is more toxic. While I easily concede that they are both extremely toxic and all efforts should be made to limit our exposure to either form of mercury,the fact remains that according to EPA's numbers, mercury vapor has a safety level that is 10x times lower than that of methylmercury.

  5. Steven. You quote Stephen Barrett - a quack, not a quack-buster - as an authourity on this subject??? and expect that to be an acceptable response to a scientific rebuttal, shame on you. You represent the worst of our society when you use your qualifications and your responsibility as a reporter to educate the general public - and you are not even capable of educating yourself first. Again shame on you. Next time learn before you open your mouth as you do a grave disservice to this subject, your fans and to your profession.

  6. Steve, are you sure you want to be associated with Barrett or any of his writings ?

    “The Court also declared that top quackbusters Stephen Barrett (quackwatch.com), and Wallace Sampson MD (Scientific Review of Alternative and Aberrant Medicine)

    “were found to be biased and unworthy of credibility.”


  7. I've skipped past the trolls and would like to simply say that I think you are far too kind to Oz. You say that:

    "...the only other explanation I can think of is that he is simply a fraud. I don't think that's true, so let's give him the benefit of the doubt and assume that when he makes a mistake, he is simply ignorant of the truth.

    How can anyone with his education be so blatantly ignorant? If this is what Harvard produces these days, remind me to send my kids elsewhere.

    Are you just being gracious to "give him the benefit of the doubt"? Professional courtesy? Well, I have no such quibbles--HE'S A FRAUD. I wouldn't let him touch my heart--or anything else.

    1. Ah Janet, it's ashame you offer no specifics and you skip past the "trolls" who've actually looked at the science and have offered concrete examples of flat out mistakes in Steve's article. Apparently he is either too proud or a fraud himself (as he likes to paint others) to recognize and change those mistakes.

  8. A one gram silver amalgam filling as it is called contains 50% mercury. Therefore there will be one half of a gram of mercury in the filling this will disburse creating 10 to the power of 20 mercury ions. Anyone one of which can bind to a tublin molecule and create disfunctional microtubules and gene expression. Because of lead toxicity the government has banned use of tetraethyl-lead in gasoline but for the last 30 years has refused to ban mercury amalgam which is the most neurotoxic substance on the planet.Yes I think everyone should be worried even the dentists.

  9. @You Put......

    Until I know your qualifications for "looking at at the science", I have no reason to think your views are anything but those of a crank, since they are in opposition to accepted science. Dr. Salzberg offers evidence and has a paper trail of his reputation, so I'll stick with him, thanks.

    1. Janet

      To promote the safety of this toxic product Dr Salzberg incorrectly identifies methylmercury as the primary form of mercury that is released from amalgam restorations. It is not even a question that the primary form of mercury escaping from amalgams is mercury vapor, because amalgams are made from elemental mercury, which releases...you guessed it...mercury vapor. (WHO 1991 and 2003, among many others). Salzberg can't even get the most basic aspects of this issue correct when trying to imply the product is safe.

      A risk assessment done in coordination with the FDA found that over 60 million Americans get more mercury everyday than what the EPA considers "safe" from their amalgam fillings (Richardson 2011)

      As far as the toxicity of methylmercury VS that of mercury vapor. The EPA has a safety level for mercury vapor that is 10 times lower than that of methylmercury... meaning it is considered more toxic than methylmercury.

      Additionally, EPA / ATSDR evacuates people from buildings when there is a mercury spill as small as what one might get from a thermometer. You can search youtube to see tv news broadcasts of this or search EPA / ATSDR for their action level and relocation level of mercury vapor.

      those are Salzbergs most glaring mistakes, which makes him the CRANK as he did not perform due diligence when writing about this subject.

  10. my dad tells a story of when he was 5 years old they would hold mercury in their palm and played with it (didn't know any better at the time). that was 60+ years ago. that doesn't mean it's safe but suggests evacuating the room comment is ridiculous!

  11. disclaimer: i know nothing about mercury or its various forms. organic, nonorganic, vapor, might be quite different.

    the case that seems interesting to back of the envelope to me is consider teeth grinding. that is going to do a lot more than the toothbrush. check my math i could easily have a mistake here:

    filling size: 2mm³
    mercury: 50% of the filling
    density of mercury: 5.43 g/cm³
    wear from teeth grinding, eating, whatever over 10 years on the filling: 20% of its mass

    (.2cm)^3 * 5.43 * 50% = ~0.02g total mercury for filling
    20% wear: 0.02g * 20% = .004g worn away and "free" for the body to (porentially) absorb
    .004g = 4000 micrograms
    4000 / 10 years / 365 days = ~1microgram/day per filling

    so what if you grind your teeth and have 10 fillings? (check my math it's probably wrong done in 60 seconds)

  12. You're more likely to die in a car accident than supposed risks from mercury fillings. Worry about something that actually kills - texting, eating, reading, radio blaring etc while driving rather than pseudo scientific warnings that have no logic. You're more likely to die on the roads going to a pseudo science conference than from the mercury in your fillings. Life is a risk, so the best thing you can do is to understand where the real risks are and try to ameliorate those with real strategies that will reduce risk.


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