Summarised by Centrist
A systematic review of 74 studies in JAMA Pediatrics found that higher fluoride levels in water and urine are linked to lower IQ scores in children.
For every 1 mg/L increase in fluoride in urine, IQ dropped by 1.63 points. This pattern was consistent across multiple countries and tested using various methodologies.
The studies spanned nations including New Zealand, China, India, and Canada, encompassing over 20,000 children.
Of the included studies, 64 reported inverse relationships between fluoride and IQ. The study found that fluoride levels below 4 mg/L in water and urine still affected IQ, even at 2 mg/L. However, at 1.5 mg/L—the World Health Organization’s recommended limit—the link to lower IQ was weaker, and in some cases, no link was found at all.
While most studies were conducted in regions with naturally high fluoride levels, such as parts of Asia and the Middle East, they align with growing concerns in Western nations. Researchers pointed out that even minimal IQ shifts at the population level could dramatically affect societal outcomes. “A 5-point decrease in average IQ could nearly double the number of people classified as intellectually disabled,” the authors noted.
The findings have sparked debate over the risks and benefits of water fluoridation. In the U.S., where fluoride is widely added to water supplies, the recommended concentration is 0.7 mg/L—well below the levels linked to cognitive effects. Still, this study adds weight to calls for a reassessment of fluoride’s safety, particularly for vulnerable populations like children and pregnant women.
Image: Parent Géry
