Ask Alina: Is Fluoride Bad For You?

Q: Can you please explain if fluoride is necessary or should it be avoided? – Naghma S. ask-alina

A: Hi Naghma, you’ve picked a pretty controversial topic! Do a quick Google search and you’ll find anti-fluoridation campaigners calling it a method of mind control and a toxic poison, while on the flip side you’ll also find dental boards and government websites saying it’s essential for dental health and perfectly safe.

Over time, I’ve learnt that the truth for most controversial topics lies somewhere in the middle and comes down to exercising a bit of caution.

What is fluoride?

Fluoride is a natural mineral that is already present in most water sources. Beginning in the 1940s, many countries chose to add more fluoride to the water supply as an efficient way to improve dental health. Research from the 1980s shows that when added in at 0.7-1.2mg per litre of water, it reduced tooth decay by 30-60% in baby teeth and 15-35% in permanent teeth. (1)

That being said, fluoride’s only benefit seems to be related to dental health, which is why it is also added into toothpaste, mouthwash and other dental products. It is not an essential or necessary nutrient.

Can too much fluoride be toxic?

For something to be deemed toxic, we have to look at the dosage. For example, water is healthy if you have 500ml, but it becomes ‘toxic’ if you drink over 10 litres in the span of an hour.

Similarly, fluoride is toxic at the following dosages: (1)

Lowest potential dangerous dose: 5 mg/kg of body weight
Lowest potential fatal dose: 15 mg/kg of body weight

Basically, this is more than 10,000-20,000 times as much fluoride is consumed at once time in a single 8 ounce glass of tap water. (2)

So, where’s the controversy?

While not immediately toxic, some studies have come to light that show the potential harmful effects of fluoride over time and also ineffectiveness.

Hypothyroidism: A study in the UK found that higher levels of fluoridation were associated with higher levels of hypothyroidism. (3) While this indicates more of a correlation than causation, to me it makes sense based on what I learned in grade 9.

Flourine and iodine (the mineral necessary for a healthy thyroid) are both in the same column and classified as halogens on the periodic table, which compete for absorption. It is then perfectly logical to assume that high flourine levels may impair iodine absorption.


Image result for halogens periodic table

Children’s IQ: another study shows that children in high fluoride areas had lower levels of IQ than children in low-fluoride areas. (4) However, it’s important to note that this study showed correlation not causation (other factors could have been at play, like arsenic in water), and most studies that were reviewed were based in China.

Ineffectiveness: The Cochrane Collaboration released a study in 2015 where they reviewed every study done on fluoridation that they could find, and analyzed these studies’ results.(5) (6)

In a nutshell, they found that prior research on dental benefits was dated. They couldn’t find enough evidence to support that water fluoridation prevents tooth decay in adults, or that it is necessary anymore given the rise of dental products with fluoride.

Research has also shown that fluoride primarily acts topically, and while toothpaste with fluoride is helpful, ingestion of water with fluoride is not. Quote from senior scientist Kathleen Thiessen: “The data suggest that toothpaste, besides other preventative measures like dental sealants, flossing and avoiding sugar, are the real drivers in the decline of tooth decay in the past few decades”. (5)

The bottom line on fluoride

It seems that fluoride’s only benefit lies in preventing cavities when applied topically, not when ingested.

So, why ingest fluoride at all then?

If you want to err on the side of caution, filter your drinking water and then it’s between you and your dentist, whether you want to use fluoride-free toothpaste or not. While I use fluoride-free, using topical fluoride doesn’t seem like a big risk to me, since you’re not eating the toothpaste.

Lastly, fluoride is not the only way to prevent cavities! Remember that there’s other ways to prevent dental cavities too:

  • Practice proper oral hygiene e.g. flossing, brushing
  • Have regular visits to the dentist
  • Minimizing intake of sugar and sugary drinks
  • Eating plenty of real, whole foods


(1) Linus Pauling Institute. (2018). Fluoride. [online] Available at: [Accessed 28 Mar. 2018].
(2) Fohey, J. (2009). Public water fluoridation. University of Northern Iowa. Available at:
(3) Peckham, S., Lowery, D. and Spencer, S. (2015). Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water. Journal of Epidemiology and Community Health, [online] 69(7), pp.619-624. Available at:
(4) Choi, A., Sun, G., Zhang, Y. and Grandjean, P. (2012). Developmental Fluoride Neurotoxicity: A Systematic Review and Meta-Analysis. Environmental Health Perspectives, 120(10), pp.1362-1368.
5) Newsweek. (2018). Fluoridation May Not Prevent Cavities, Scientific Review Shows. [online] Available at: [Accessed 28 Mar. 2018].
(6) Iheozor-Ejiofor, Z., Worthington, H., Walsh, T., O’Malley, L., Clarkson, J., Macey, R., Alam, R., Tugwell, P., Welch, V. and Glenny, A. (2015). Water fluoridation for the prevention of dental caries. Cochrane Database of Systematic Reviews. [online] Available at: [Accessed 28 Mar. 2018].

About Alina

I'm a Holistic Nutritionist based in Toronto, Canada and my official title is Certified Nutritional Practitioner (CNP). I received my diploma in Applied Holistic Nutrition from the Institute of Holistic Nutrition. I'm a coach and an educator. Follow Alina on Facebook, Twitter, Pinterest and Instagram for all of the latest updates.
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