The presence of fluoride in drinking water, or even its addition in some countries (a common practice to prevent cavities), is raising concerns today. A recent study suggests that exposure to fluoride, particularly during pregnancy and early childhood, could affect children's brain development.
For decades, many countries, such as the United States, Canada, and Australia, have been adding fluoride to their drinking water systems. However, this public health measure, although effective for dental health, is being questioned by new research. A team from the Karolinska Institute in Sweden has studied the impact of fluoride on cognitive development, revealing concerning results.
Fluoride in water: a widespread but contested practice
Fluoride is naturally present in water, but often at concentrations too low to prevent cavities. To address this, some countries add fluoride to their drinking water systems, at levels of about 0.7 mg per liter. This practice, although deemed safe by health authorities, remains controversial.
Maria Kippler, associate professor at the Karolinska Institute, points out that even relatively low concentrations of fluoride could influence early childhood development. Critics particularly highlight potential risks to cognitive health, which might outweigh the dental benefits.
A revealing study conducted in Bangladesh
To assess the impact of fluoride, researchers followed 500 mothers and their children in a rural region of Bangladesh, where fluoride is naturally present in the water. They measured fluoride levels in the mothers' and children's urine, then evaluated the children's cognitive abilities at ages five and ten.
The results show that high levels of fluoride in mothers were associated with reduced cognitive abilities in their children. The most affected areas were verbal reasoning and sensory processing, essential for learning and communication. These effects were observed at fluoride levels significantly lower than the safety thresholds defined by the WHO and the EU, set at 1.5 mg/L.
Long-term effects
The researchers noted that fluoride levels in five-year-old children were not strongly correlated with their cognitive performance. This could be explained by a shorter duration of exposure or variable absorption of fluoride in young children.
On the other hand, at ten years old, children with fluoride levels above 0.72 mg/L showed significant cognitive deficits. These results highlight the complexity of fluoride's effects on development and the need for further research to better understand these mechanisms.
To go further: how does fluoride affect the brain?
Fluoride, crossing the placental barrier, can reach the fetus during pregnancy. Once in the body, it could disrupt neuronal development by interfering with communication between brain cells. Animal and epidemiological studies suggest that fluoride particularly affects brain areas involved in language, memory, and sensory perception.
The precise biological mechanisms remain to be elucidated, but some hypotheses point to a disruption of enzymes and proteins essential for neuronal function. For example, fluoride could alter the production of neurotransmitters, the molecules that allow neurons to communicate with each other. This would explain why children exposed to high levels of fluoride present difficulties in areas such as verbal reasoning or sensory comprehension.
Moreover, fluoride could influence brain plasticity, that is, the brain's ability to adapt and remodel itself based on experiences. This plasticity is essential during childhood, a period when the brain develops rapidly. Excessive exposure to fluoride could therefore limit this adaptability, durably affecting learning and cognitive abilities.
Finally, the effects of fluoride on the brain could vary depending on age and sex. Some studies suggest that girls might be more sensitive to the effects of fluoride than boys, although this difference is not yet clearly established. These variations highlight the complexity of the interactions between fluoride and brain development, requiring in-depth research to better understand these mechanisms and their long-term implications.
Article author: Cédric DEPOND