You no doubt read in all the newspapers reports last week about the two articles in JAMA (click here for full text of one and here for the abstract of the other) showing that there was no need to worry about letting the dentist fill your kids’ teeth (or your own) with mercury amalgams because, well, because two large studies showed no negative effects in multiple parameters between kids who had mercury fillings and kids who had resin fillings.
It seems kind of strange to me given that mercury is an extremely toxic substance that putting large amounts of it into the body (especially the body of a child) wouldn’t cause some kinds of problems somewhere along the line. What do these papers tell us?
The first one evaluated groups of children in the New England area who had fillings done with either mercury amalgams or with a resin material containing no mercury. Researchers evaluated these two groups of children for any changes in intelligence as measured by standardized intelligence tests over a period of five years. As might be expected, the children with the mercury amalgams had greater levels of mercury in their tissues as measured by hair and urine samples.

Children assigned to the amalgam group had a significantly higher mean (SD) urinary mercury level 5 years after baseline than did children assigned to the composite group (0.9 [0.8]; range, 0.1-5.7 µg/g of creatinine vs 0.6 [0.5]; range, 0.1-2.9 µg/g of creatinine, P
The interesting question is how did the non-amalgam treated group end up with so much mercury? Probably from vaccinations. At the time this study was done all children were getting a panoply of vaccinations all of which contained thimerosol, a mercury-containing preservative. These findings beg the question as to whether or not the study outcomes were truly valid since both groups had fairly significant levels of mercury.
The researchers looked at the changes in intelligence over five years in these children and found that, if anything, the group who had the amalgam fillings increased their intelligence more (my italics) than did those who didn’t get the mercury fillings.

Full-scale IQ, general memory index, and visuomotor composite scores increased between the baseline and 5-year assessments in both treatment groups. None of the differences between the change scores in the 2 treatment groups, adjusting for baseline score and randomization stratum, were statistically significant, although for all 3 tests, the differences favored the amalgam group (Table 3). Adjusting for additional covariates did not change the results appreciably.

There was no statistical difference in the intelligence changes between the two groups, but if the actual statistical analysis is examined an interesting thing pops out: the confidence intervals are huge. A large confidence interval means that the data was all over the place. Even though the differences overall were not statistically significant, based on the large confidence interval, many children were at the extremes. What this tells us is just what we would expect. Most kids aren’t affected by the amounts of mercury found in the amalgams, but some are. It’s these kids who are, who are much like the canaries in the mine shafts, whom we worry about. It’s like a pack of wolves or other predators circling a herd of elk; the young, old and sick (i.e., the most vulnerable) are the ones that get nailed. The strong, healthy elk aren’t bothered. It’s the same with a toxic insult such as mercury–it’s the vulnerable kids that are affected. Despite the fact that the averages don’t change, some kids can be adversely affected and not have it show up in a study such as this one.
The other study published in the same JAMA issue took place in Portugal where the researchers followed and compared two groups of children–one with mercury amalgams and one without–for seven years looking at memory, ability to focus, visuomotor functions and nerve conduction velocities. As in the first study the children with the amalgams had significantly higher levels of mercury in their tissues, but no statistically significant differences in the parameters of neurological function measured. And like the first study the confidence intervals were wide, indicating a wide distribution of findings. Once again, I’m sure some of the most vulnerable children had problems. It would have been nice to have seen all the data instead of just the tabulation.
In the most recent issue of The American Journal of Forensic Medicine and Pathology there appeared a paper throwing more light on this subject. As the researchers reported:

It rarely occurs that issues such as mercury, dental amalgam, or possible amalgam neurotoxicity may indeed reach the forensic scenario. However, scientific data have given us reason to at least consider the fact that dental amalgam may be a poison, in the strictest medicolegal sense, and that therefore its mode of distribution and accumulation within the body and consequential toxic effects could indeed have relevance from medicolegal perspective. However, much of the possible cause-effect concatenation still has to be proven, and the authors would like to briefly illustrate the results of the present pilot study to stimulate consideration of this issue, in other words as mere “food for thought.”

The authors of the study went on to describe the wealth of literature showing the correlation between mercury amalgams and tissue mercury levels. After summarizing the literature, they had this to say:

In essence, amalgam fillings have been shown to contribute to approximately two-thirds of the human body burden of mercury.

These researchers then analyzed the tissue mercury content of cadavers at autopsy and compared it to the number of mercury amalgam fillings. The reason this study is so important is that it is difficult to determine the amount of mercury in the tissues of living people because blood levels aren’t a particularly accurate way to measure it. Neither are urine and hair. Most of the mercury stays locked in the tissues, especially brain tissue, making it problematic to measure since most people aren’t eager to queue up for a brain biopsy, the only real way to find out.
Since corpses don’t much mind a brain biopsy the data these researchers uncovered is, in my opinion, invaluable. They found that there was a direct correlation between the number of fillings and the amount of mercury in the bodies. And they found that most of the mercury was in the brain with lesser amounts in the thyroid gland and kidneys.
As they put it:

Mercury levels increased with the number of dental amalgams for all the anatomic sites. The interaction term between each anatomic site and the number of occlusal amalgam surfaces was statistically significant (P = 0.03), suggesting that the association between mercury levels and the number of occlusal amalgams was dependent on the anatomic site. Mercury levels in the pituitary gland and the cerebral cortex in subjects with more than 12 occlusal amalgam surfaces were more than 10 times higher than levels in subjects with 3 or less occlusal amalgams (both P = 0.0007). Levels in the thyroid and in the renal cortex were respectively about 5 and 4 times higher in subjects with 12 occlusal amalgams or more compared with subjects with 3 occlusal amalgams or less (P = 0.01 and P = 0.04, respectively).

And their conclusions after a long discussion of the neurotoxic effects of mercury:

In summary, our research shows, for the first time, that frontal lobe cortex has the highest content levels of mercury associated with occlusal amalgam surfaces and total mercury levels approaching or exceeding 300 ppb (ng/g), wet weight, in some cases. This, in turn, strongly points to the hypothesis–which, in the future, should be looked into in larger and ad hoc studies–that mercury vapor, known to be a neurotoxicant, may indeed lead to some types of neurobehavioral disorders.

Now, I don’t know about you, but I’m not all that keen to have mercury amalgams. I may be one of those who can withstand the mercury; in fact, I probably am because I had mercury amalgams as a kid, but had them removed and replaced years ago. When I had them in place, they didn’t seem to do me any harm, but who knows, without them I might have become a rocket scientist.
I certainly wouldn’t expose any of my children or grandchildren to mercury amalgams just because JAMA came out with a couple of articles claiming that they were harmless. Mercury is toxic, of that there is no question. The amalgams produce mercury vapor, of that there is no question. People with mercury amalgams have higher levels of tissue mercury, of that there is no question. So why inflict children (or yourself) with a poison that is for sure going to go to their brains? Even though it might not harm them.
An even better method is to keep your children away from sugar and refined carbohydrates, make them practice good dental hygiene, and prevent cavities in the first place, then you won’t have that decision to make.


  1. “When I had them in place, they didn’t seem to do me any harm, but who knows, without them I might have become a rocket scientist.”
    Rocket science is NOT your forte. Your forte is what you are doing right now! Keep it up, you (and your wife) are brilliant. Please don’t become a rocket scientist, we need you here.
    I am a person who has had mercury amalgam fillings in EVERY one of my teeth for my entire life. My entire diet (as a child) consisted of sugar, and I had at least 10-20 cavities per year to show for it. Giant dental bills.
    In the scant 2 years that I have been eating low carb (40 yo), my severe periodontal disease has dissappeared. No cavities, no pockets, no fillings, no diseased teeth, and no surgery. My Dentist is not amazed, as they all do low-carb at their office and know that dietary glucose/starch/carbs is poison.
    I have broken a few mercury thermometers in my day- mostly because I was trying to heat them up artificially to get a day off from school. I remember cleaning up those beautiful rolling blobs of mercury from our bathroom floor, hoping that I wouldn’t get in trouble.

  2. I was unaware that there were acceptable subsitutes for mercury amalgram. It seems a no brainer that they (composites) should be used instead of amalgram just like we eliminated lead from gasoline (although from what I understand, its toxicity was well known when it was first used in gasoline in the 1920’s). Given the tendency for mercury to accumulate in the brain, I wonder if anyone has tried to link it to Alzheimer’s? An internet search found the following articles.,6,9;journal,85,406;linkingpublicationresults,1:101493,1,10,10;journal,20,73;linkingpublicationresults,1:100146,1
    The last, The Three Modern Faces of Mercury, is a good summary article. It indicates that relationship of mercury to dementia is at this point uncertain. It does have some interesting items. Excessive gum chewing is linked to higher release of gaseous mercury from amalgram. Alcohol consumption inhibits absorption of mercury vapor. Selenium and some other antioxidants block the absorption of mercury. Some evidence has been found linking mercury levels in the body to heart disease. It is interesting that both antioxidant status and alcohol intake have been found to be negatively correlated to heart disease.

  3. Hmmm, I saw the article in the paper and was suspicious about the findings and this just confirms it. Really makes me glad that I had no cavities as a little kid (my brother and sister were not so lucky.) Later on, my orthodontist capped some of my primary molars a few years before they fell out when they had some cavities starting rather than drilling and filling them. I don’t know if the fact that he was in Mexico had anything to do with that. Now I’m wondering if I should have the few mercury fillings that I got as an adult replaced. I’ll have to explore that with my dentist next month when I see him. My sister had all hers replaced because of her MS (I guess she figured that it couldn’t hurt.) Meanwhile, I really wonder just how healthy it is to have root canals done. The one root canel that I had eventually went bad with a very nasty abcess- an experience that I would wish on no one-and I finally had them pull the tooth rather than having it redone like they wanted to do. BTW, for what it’s worth, I am the only one of my siblings that hasn’t had peridontal disease.
    Thanks, Mark, for posting the links as they should be interesting reading.
    And I agree with Karen, I am glad that you did not become a rocket scientist as we do need you here!

  4. Hmmm….no cavities because low carb in low sugar. I never thought of that connection! I know I have quite a few cavities from a checkup I had several years ago, but because I am so afraid of the dentist I decided not to do anything about them unless they DID become a problem.
    Yeah, I’m a wuss.

  5. Dr.s Eades, I purchased your diet plan about 6 or 7 years ago. I did well on it, but fell off of the wagon. I am getting started on it again now. I have one problem… my kit came with cassette tapes & I no longer have a cassette player. Is it possible for me to order the tapes on cd? I feel like my biggest problem with most diets is I quit before I get to maintenance. I want to go through the whole diet & do the maintenance so I can keep the weight off. I know I will need a lot of encouragement & I have set myself up a network of friends to help me. Thank you for your Protein Power Plan, it is a great plan.

  6. Thanks for the kind words about Protein Power. We do indeed have CDs now that we’re working on making available through our website. Keep watching.

  7. Dr. Eades, you have honed it on the critical issue in these bogus studies: what is the data on the vulnerable subset of children.
    Dr. Boyd Haley, former Chair of the chemistry department at the University of Kentucky has done an excellent examination of these studies – especially as it relates to susceptible subsets of subjects. you can find it at:
    Dr. Haley has done a lot of research on mercury and its effects on the body. He is an expert witness for parents of autistic kids who were harmed by the mercury in vaccines. Dr. Haley also believes, based on extensive research, that mercury is the primary cause of Alzheimer’s.
    There is a subset of people with a certain APOE genotype who cannot effectively detox mercury. In kids it shows up as autism. You don’t find much mercury in their urine or in their hair …. it is retained in their bodies. And in old people it manifests as Alzheimer’s.
    The kids in the Children’s Amalgam Trials had an average amount of mercury in their urine which Diane Echeverria, et al, found in DENTISTS to cause measurable neurological deficits.
    The investigators did porphyrin tests on these kids (a sign of mercury toxicity), but they didn’t publish the results. Dr. Haley thinks that is the smoking gun.
    I am a public lawyer, but also a board member of Consumers for Dental Choice, a private non-profit working to abolish the use of mercury in dental fillings.
    I have prepared a Freedom of Information Act request to be sent to the University of Washington (Portuguese part of the study) and National Institute of Dental and Craniofacial Research – which spent $11 million of taxpayer money to poison poor, mostly minority children in New England, and orphans and handicapped kids in Portugal, some of whom were the victims of sex abuse.
    Thanks for passing the word.
    Sandra Duffy
    Lake Oswego, OR
    My pleasure
    Thanks for writing.

  8. the most accurate research that could be done on amalgam would be to require all dentists who use it to place a generous research amount in their own mouths. then , with no measurable increases in their body burden of mercury, we can debate and ponder why they sometimes run their spouses over with their mercedes in fits of rage, a symptom associated with mercurialism.

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