Is Fluoride Bad for You? Effects for Thyroid & Body

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The effects fluoride has on the thyroid and body
Wellness Mama » Blog » Health » Is Fluoride Bad for You? Effects for Thyroid & Body

You likely know that mercury, lead, and other heavy metals are not great for the body and can cause a host of issues. But whether or not fluoride is safe (or effective) is more controversial.

Is Fluoride Beneficial?

In the early part of the twentieth century, it was discovered that small communities who had higher levels of naturally occurring fluoride in their drinking water had fewer dental caries (cavities). Naturally fluoridated water at about 1mg/L seemed to be beneficial to dental health. (Fluoride that is naturally occurring is calcium fluoride.)

Unfortunately, the fluoride that is often added to water supplies in the U.S. is hydrofluoric acid (an industrial by-product), not elemental fluorine or calcium fluoride. It’s well known that naturally occurring substances (even heavy metals) are generally better tolerated by the body than synthetic counterparts.

But because early studies showed few dental caries in communities using fluoridated water, fluoridated water became known as one of 10 best public health achievements of the twentieth century according to the Center for Disease Control (CDC).

However, rates of dental caries have been going down for all western countries, both using fluoridation and not, suggesting that there is no connection between fluoridated water and fewer cavities.

For example, Sweden does not fluoridate its water and has the same amount of dental caries as the United States. Nobel Prize Winner Dr. Arvid Carlsson argued against its use in Sweden by saying that topical use of fluoride may work for dental caries but drinking fluoride was not a good idea, especially when you consider that the amount any individual consumes can vary quite a bit.

Though some earlier studies showed that fluoride in the water supply can help reduce dental caries, a 2015 Cochrane review found that the most recent and comprehensive evidence shows that there is simply not enough evidence to support fluoridating water.

Though fluoride may help prevent cavities when used topically, there are other (better) ways to improve oral health without fluoride.

Sources of Fluoride

Fluoridated water is an obvious source of fluoride but there are many others as well. Because there are so many sources of fluoride today, it’s especially concerning that water supplies are “spiked” with fluoride. Here are some of the major sources of fluoride:

  • Packaged foods and drinks (made with fluoridated water)
  • Pesticides
  • Tea (the plant naturally absorbs fluoride; herbal teas are fine)
  • Teflon pans
  • Mechanically separated meat (fragments of bone can be left behind)
  • Industry (aluminum, fertilizer, iron, oil refining, semi-conductor, and steel industries)
  • Fluorinated pharmaceuticals (the fluorine doesn’t usually break down into fluoride, but may)
  • Dental products

Of course, there are reasons other than fluoride to avoid some of the things on this list. For someone who is interested in natural health (and avoiding many of these things already), avoiding fluoride isn’t all that hard.

How Fluoride Affects the Thyroid

Though there is some debate about whether fluoride is safe, the evidence is pretty clear that it can affect thyroid function, and for anyone at risk to begin with (many women are), fluoride is potentially dangerous. Considering thyroid disease affects 20 million Americans (mostly women), this is an important angle to consider.

In the 1930s a product containing fluoride was used to treat people with hyperthyroidism (overactive thyroid). The fluoride poisoned the enzymes in the thyroid gland and slowed down the production of thyroid hormones. This drug stopped being used because some people’s thyroid glands were permanently damaged from its use.

Studies show that fluoride affects the thyroid gland specifically. Studies done in India found that children in communities with high fluoride intake had a significant decrease in thyroid-stimulating hormone (TSH). Another study found that people with unfluoridated water were less likely to develop hypothyroidism.

Fluoride and Iodine

Fluoride can lead to thyroid inflammation and autoimmune thyroid disease (like Hashimoto’s). Fluoride is also an endocrine disruptor. Dr. Izabella Wentz explains in this post how it’s misidentified as iodine in the body so it is taken up into the body and stored in body tissues the way iodine should be.

One study found that iodine levels directly impact how much harm fluoride can do to the thyroid and may help protect the thyroid from fluoride. On the other hand, many people who have thyroid disease like Hashimoto’s have low levels of iodine but can’t tolerate supplemental iodine either. In those cases, fluoride is particularly problematic.

How Fluoride Affects the Skeletal System

Fluoride is also fairly clearly implicated in bone health issues. Though supporters of fluoride claim that it can help improve bone density, evidence shows that the amount of fluoride plays a very important part in whether fluoride helps or hurts bone health.

This study looked at different populations in China with varying levels of naturally occurring fluoride in the water ranging from 0.25 mg/L to 7.97 mg/L (as a comparison, places that add fluoride to water typically add to .7-1 mg/L). What the study found was that fractures happened less when fluoride levels were at about 1 mg/L but more when they were on the lowest and highest parts of the range. Clearly, there’s a fine line between helpful and harmful here.

Skeletal fluorosis is a serious bone disease which causes hardening and thickening of the bones which makes movement difficult. It can be confused with a number of other skeletal issues including arthritis. Skeletal fluorosis is caused by excessive exposure to fluoride which can happen over time as fluoride can accumulate in the body. The most recent research shows that early signs of skeletal fluorosis can occur with as little as 6 mg of fluoride a day (much less for those with kidney disease).

The Upside

Having good health to begin with, particularly normal levels of vitamins and minerals, can help reduce the negative effects of fluoride. One study found that normal levels of calcium helped prevent fluoride-induced bone issues in rats. Another found that sufficient levels of vitamin D could be protective. Additionally, another study found that magnesium-deficient rats absorbed more fluoride than rats with normal magnesium levels and also had more fluoride in their bones and teeth.

What does this mean? That we can do something about fluoride exposure by doing some of the same things that are good for health overall. Optimizing calcium, vitamin D, and magnesium levels (here are some ideas on that) and eating a nutrient-dense diet is a great first step.

Fluoride and the Brain

Fluoride is a confirmed neurotoxin and many prestigious reviews have dug into the research that is available on the topic over the years. A 2012 Harvard review found that of the 27 studies in the review, 26 of them concluded that there is a relationship between elevated fluoride and reduced IQ.

A 2014 Lancet review documents fluoride as a neurotoxin that could be harmful to child development. The review concludes, “The presumption that new chemicals and technologies are safe until proven otherwise is a fundamental problem.”

Newer research is finding the same neurotoxicity problems as earlier studies. A 2017 study found that fluoride exposure in utero was linked to poorer cognitive performance later in life.

Fluoride Affects Other Parts of the Body

While the effects of fluoride on the thyroid, skeletal system, and brain is fairly clear cut, the science is less clear on how fluoride affects other parts of the body. Here are some other ways fluoride may cause harm:

  • Cancer – A connection between fluoride and cancer is a hotly debated topic, probably because the research is inconclusive and at times confusing.
  • Early sexual development – One researcher found that fluoride accumulates in high amounts in the pineal gland (that secretes hormones). A 1997 study found that fluoride was associated with faster sexual development in the female gerbils in the study.
  • Male infertility – Some data suggest that a decline in male fertility could be associated with topical fluoride use. Animal studies show concern but more information is needed.

So… Should I Be Worried About Fluoride?

There are many conflicting opinions on whether fluoride is safe and whether it’s something to worry about. (I know, you hear me say things like that a lot!) Mark Sisson’s opinion on it is that fluoride isn’t great but that we should focus on improving health in other ways first (clean diet, plenty of sleep, low stress, etc) before worrying about filtering fluoride from the water. On the other hand, if you are filtering your water because of any number of the other pollutants that could be in it, you may as well filter out fluoride too.

There is evidence on either side of the debate. My personal stance is that for people with thyroid issues (like me) it’s clearly best to avoid fluoride. And since fluoride does come with a warning to call the poison control center immediately if ingested (and after seeing a close friend’s scare when her son ingested some fluoride), I buy unfluoridated toothpaste and don’t keep fluoride-containing products around our house.

How to Protect Teeth Without Fluoride

Though fluoride may have a protective effect on teeth, there are other (better) ways to keep teeth healthy than to smear them with fluoride.

Dental Diet

What you eat can impact your oral health even more than brushing or flossing. Teeth are in a constant state of remineralization as the saliva in the mouth provides minerals to the teeth and the cells in the teeth use these minerals to strengthen themselves.

Diet can play a huge part in this process (and the health of your teeth). According to Weston A. Price’s (and others) research, a diet rich in healthy fats, vitamins, and minerals can help heal and protect oral health. I go into more detail in this post.

Balancing Hormones

Hormones can have a huge effect on oral health as they can control the acid/alkaline balance in the mouth. They also affect how well the body can heal from or fight disease. Many of us have symptoms of hormone imbalance and things like optimizing sleep, stress, diet, and fitness can make a big difference in hormone health (and oral health).

Homemade Toothpaste

Many conventional kinds of toothpaste contain chemicals and artificial ingredients that can do more harm than good! That’s why I started making my own remineralizing toothpaste. I’ve been using it for years and have had no new cavities (and have even healed some that were waiting for a filling).

Fluoride-Free Toothpaste

Of course making your own toothpaste isn’t always practical when life gets busy, so I created my own line of personal care products based on my DIY recipes. It’s called Wellnesse and my Whitening Toothpaste is fluoride-free (but fights bacteria and decay with green tea leaf extract instead!).

Fluoride: Bottom Line

There’s lots of conflicting evidence surrounding fluoride and fluoridating water. Some agencies and dentists think fluoride use has been a huge health advancement. But there’s also growing evidence that fluoride can be harmful. I like to go on the side of caution (especially when there are natural ways to improve oral health) and avoid it. We use a water filter that removes fluoride as well.

This article was medically reviewed by Dr. Scott Soerries, MD, Family Physician and Medical Director of SteadyMD. As always, this is not personal medical advice and we recommend that you talk with your doctor.

This article was medically reviewed by Dr. Terry Wahls, a clinical professor of medicine and clinical research and has published over 60 peer-reviewed scientific abstracts, posters, and papers. As always, this is not personal medical advice and we recommend that you talk with your doctor.

Do you use fluoride? Why or why not?

Katie Wells Avatar

About Katie Wells

Katie Wells, CTNC, MCHC, Founder of Wellness Mama and Co-founder of Wellnesse, has a background in research, journalism, and nutrition. As a mom of six, she turned to research and took health into her own hands to find answers to her health problems. is the culmination of her thousands of hours of research and all posts are medically reviewed and verified by the Wellness Mama research team. Katie is also the author of the bestselling books The Wellness Mama Cookbook and The Wellness Mama 5-Step Lifestyle Detox.


17 responses to “Is Fluoride Bad for You? Effects for Thyroid & Body”

  1. jen Avatar

    The own study you cite says that fluoride should still be used in toothpaste to fight cavities. I mean at least you’re transparent enough to include that but it’s still disingenuous and downright moronic to make a fearmongering post against fluoride toothpaste (since that’s what you’re selling – fluoride toothpaste) and then cite a study that specifically says to use fluoride on teeth and only talks about the downsides of fluoridated water, which as you admit has nothing to do with fluoride toothpaste.

    1. Katie Wells Avatar

      I’m not sure what you’re referring to as I don’t sell or recommend any toothpaste with fluoride in it, as it’s a toxic ingredient that I would never recommend…

  2. Janelle Avatar

    I really like that you did research before writing this article & I am super passionate about health, just as you are! As a current student in dental school with a history of working in the dental field, I do think some of the articles are “cherry picked”. From the research I have been presented at school and have seen on my own, many studies on negative effects of fluoride have flaws in the ways that the research was conducted, have small sample sizes, etc. Just with anything else, I believe moderation is key.
    I would personally recommend the use of topical fluoride (in toothpastes & at dental visits 2x per year) as a means for maintaining dental health. You aren’t ingesting it and the fluoride in these applications helps strengthen minerals in the enamel (white, outer layer of the tooth), making the enamel stronger than it is without fluoride. As you may know, enamel does not repair itself so once it is lost, your teeth become substantially weaker and more vulnerable to the pH of the mouth and bacteria. [Another reason why I recommend drinking certain beverages with a straw! Kombucha, wine, sparkling/ even some bottled waters like Dasani (if the pH is lower than 5.5 take caution!) and advise not to use abrasive whitening toothpastes].
    If you are concerned about your overall intake of fluoride, maybe look at drinking water that does not contain fluoride, but be aware that most water filters that are commercially sold do not filter out fluoride. You can also check to see the level that your city is adding to its water, which should be around 0.7 mg/L for optimal dental health. Alternatively, you could consider brushing with fluoridated toothpaste at night, and fluoride-free during the day (nighttime is when you salivate less so bacteria sits on your teeth releasing those detrimental acids). For children, using a smear of toothpaste that is “the size of a grain of rice” will ensure that, even if swallowed it won’t have harmful effects. Once they can spit on their own, use a pea-sized amount.
    There are many sources out there, including documentaries that use false information not backed by research, which is not only concerning, but super misleading. Some documentaries even interview health care professionals who you would think you can trust, but if you research these individuals, many have lost their licenses and can no longer practice.
    I feel as though if you are making an effort towards taking care of your teeth, you are already a step in the right direction. Just make sure to always do your research through a reliable database like PubMed, MedLine, Cochrane, etc., respect your health care professional’s opinion, and still take everything with a grain of salt. Do what works & feels good for YOU! I hope some of these tips were useful for some viewers.

    1. Betty Grey Avatar
      Betty Grey

      Here in the UK they don’t put Fluoride in our tap water. I use Caledula toothpaste which is a homeopathic one by Weleda which does not contain Fluoride and is also mint free which I like.

      It’s the only one I use because I can’t stand the bitter taste of mint in my mouth which Fluoride toothpaste has. I also clean my teeth without toothpaste with just tap water on my brush. As one dentist said it’s not the toothpaste you use that keeps plague away it’s the brush. Which is true and there is no evidence that using a Fluoride toothpaste improves the outcome and prevents tooth problems.

        1. Betty Grey Avatar
          Betty Grey

          Gosh. I did not know you made your own toothpaste. Your are very clever. A lot of the dentists told me I must use a Fluoride Toothpaste and they did coat some of my teeth(which I have already lost) with desentitizing Fluoride Varnish. Which was supposed to take away the sensitivity from the tooth. But it obviously did not work for me as they still came loose in the end and I lost them anyway.

          Even when I was using ordinary toothpaste with Fluoride I still had the same problems with my teeth. The Weleda Toothpaste I have now started using has Calendula and Myrrah. Caledula is for senestive teeth which I have and the Myrrah helps the gums that are senestive and prevents infection. And it does not have mint in it which is what I want.

          But most other toothpastes including herbal do have mint in that’s what I don’t like. There are some strawberry and vanilla flavored toothpastes that are mint free. But these are for children and I do not think it good to use them as they might have sugar in. And you would not brush your teeth with sugar so you would not want that in a toothpaste. So I think the Weleda one is best as it has the herbal tinctures Calendula and no sugers in it unlike the kids ones from the chemist.

  3. Greta Avatar

    When people say to me that every time they go to the dentist they have a filling. I then ask if they use fluoride toothpaste which they usually don’t.
    One example is a healthy lad who I saw 6 months previously with no decay. 6 months later after using no fluoride toothpaste he had aggressive decay and the only thing he had changed was to use fluoride free toothpaste.
    I understand the concerns about adding fluoride to water but not with toothpaste. You should not swallow toothpaste.
    Unfortunately most foods have sugars including fruit, fruit juice, carbs, etc. To be effective at reducing decay people need to realise that time spent on cleaning teeth properly is extremely important. Most people have not been taught to use effective plaque control which includes a systematic approach on teeth and gums. U

    1. Kathleen Kahl Avatar
      Kathleen Kahl

      Interesting because I had the opposite experience. I use fluoridated toothpaste up until my early 30’s when I learned it is a neurotoxin and there are no conclusive studies showing it improves health. I went from getting cavities a lot to not getting them anymore. I bore my Dentist twice a year though. I use a water filter that removes it called Clearly Filtered.

  4. Anastasia Avatar

    Very interesting! I have been trying to research water and how I can improve my drinking for some time now. Core Spirit has an interesting article about bottled water. They say it’s bad for you and everyone should go for tap water instead.

  5. Jess Avatar

    What are your thoughts on fluoride varnish at dental visits twice per year? Do they use elemental fluorine or calcium fluoride in those? I know it’s usually a sodium fluoride varnish, so I assume it’s not the naturrally occuring type…

  6. Bill Baltar Avatar
    Bill Baltar

    We just ordered replacement fluoride filters for our Berkey water purifier. I think the Berkey recommendation is to replace the fluoride filters once each year. The cost is about $55. Bill in Jacksonville, Florida

    1. Dorothy Avatar

      The berkey fluoride filters cannot remove fluoride out of water. I had a friend tell me that it’s to small to filter out that way, he worked for a water treatment plant all his adult life. When I checked online, others had their water tested and no change in fluoride levels after going they the berkey filters with the fluoride filters. I was very disappointed when I found this out. I have not contacted the company yet about this.

      1. Sparky Avatar

        I’d love to know if this is true, or even probable? I was considering buying the berkey fluoride filter…

  7. Megan Avatar

    What about the flouride pills the doctor wants to prescribe for my child? We have well water so no flouride in it. But they are really pushing that she chew the pills daily for her teeth.

      1. Grena Avatar

        I don’t fully agree with everything in this article either. I am with the people the toothpaste is OK but not in water. But fluoride tablets that you chew and will likely swallow a fair bit of? Hell no.

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