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?


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  2. Li, Y., Liang, C., Slemenda, C. W., Ji, R., Sun, S., Cao, J., . . . Johnston, J. R. (2001, May). Effect of long-term exposure to fluoride in drinking water on risks of bone fractures.
  3. Estimated “Threshold” Doses for Skeletal Fluorosis. (n.d.).
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  6. Impact of fluoride on neurological development in children. (2014, December 22).
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  14. Main, D. (2016, April 06). Fluoridation May Not Prevent Cavities, Scientific Review Shows.
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*Original article online at

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