Will Fluoridated Water Affect my Child’s IQ?

To know what fluoride is and why our water is fluoridated, check out our last Fact Friday post here. Today’s post reviews the current research on whether drinking fluoridated water will affect a child’s IQ.

A recent Canadian study looked at the association between consumption of fluoride by pregnant women and their child’s IQ. From 601 mother-child pairs in six cities, they looked at how much fluoride the mothers consumed, how much was in their urine, and then tested the child’s IQ at age three [1]. To simplify, what they found was a slight decrease in IQ when the mother’s urine had a bit more fluoride a. This was only the case for boys, not girls. However the child’s IQ (regardless of sex) slightly decreased when the mother’s daily fluoride intake was higher b.   

So does this mean I should avoid fluoride while pregnant?

In the realm of research, we investigate to add to our knowledge. While this study presents that there is a potential association, we cannot prove that it is definitely true or that there is a risk with just one study. 

This study has some limitations: 

  1. Some key measurements were off – fluoride intake did not match urinary fluoride, i.e. we don’t know exactly how much fluoride the mothers were consuming to make a conclusion. 
  2. The decrease in IQ only affected the boys it is very unclear why fluoride consumption would not affect girl’s IQ as it did in the boys, although similar studies did not find a difference in sex as they did. 
  3. Previous studies had fluoride levels way above acceptable limits in Canada – these studies took place in regions where water fluoride concentrations are well above the guideline (1.5mg/L) [2]c.  
  4. High fluoride in 3 urine samples ≠ exposure to baby three urinary samples from the mother do not reflect the overall exposure of fluoride to the fetus over the whole pregnancy. 
  5. They did not take into account different ways of intaking fluoride: As mentioned, fluoride is present in toothpaste, mouthwash, some bottled water, and food i.e. measurements were off. 


Though we can’t make conclusions based on one study, we can continually review what level of fluoridation is best for us. Based on years of research, we know that drinking optimally fluoridated tap water in Canada is safe, improves oral health and is better for the environment than bottled water!

a Results: With an increase of 1mg/L of maternal urinary fluoride they found an associated decrease of 4.49 points in their child’s IQ, but only when the child was a boy, and not in girls.

b When mother’s daily fluoride intake increased by 1 mg, they found an associated decrease of 3.66 points in their child’s IQ (regardless of sex).

c The researchers try to back up their results by quoting studies that have observed a similar association. But these studies took place in regions where water fluoride concentrations are well above the guideline of 1.5mg/L (the highest acceptable amount in Canada), while the study conducted in Mexico did not report a concrete fluoride value at all [3]. 

Please be aware that these are general guidelines. Nutrition and intake varies by age, sex, height, activity, being pregnant or breastfeeding, and medical conditions. For more information or to sit with one of our dietitians for an individualised nutrition counselling session, please contact us at amananutrition@gmail.com or visit our Contact Us page to book your first appointment.

Until next time,

Almas-Sadaf Shaikh, PMDip, RD


[1] Green R, Lanphear B, Hornung R, et al. Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada. JAMA Pediatr. Published online August 19, 2019. doi:10.1001/jamapediatrics.2019.1729.

[2] Health Canada (2017). Fluoride and Oral Health. [online] Available at: https://www.canada.ca/en/health-canada/services/healthy-living/your-health/environment/fluorides-human-health.html

[3] Bashash, M., Thomas, D., Hu, H., Angeles Martinez-Mier, E., Sanchez, B. N., Basu, N., … & Liu, Y. (2017). Prenatal fluoride exposure and cognitive outcomes in children at 4 and 6–12 years of age in Mexico. Environmental health perspectives, 125(9), 097017.