Fluoride does not have negative effect on intelligence

It is a well-known fact that fluoride is good for the teeth. Two researchers at Uppsala University show in a working paper from IFAU that a higher level of fluoride in the drinking water does not lead to lower intelligence.

Earlier international research has indicated that there is a connection between a high level of fluoride in the drinking water and lower intelligence. Using a large Swedish data material, the resarchers compare children who during their childhood and adolescence in the 1980's and the 1990's have consumed different amounts of fluoride in the drinking water.

As expected, the researchers find that the dental health is better for those who have lived in areas with a higher level of fluoride. However, there is no support for the levels of fluoride having any negative effect on intelligence, measured as men's cognitive ability when enlisting, or school results measured as the result on the national test in mathematics in ninth grade.

- Our study is the largest of its kind and we do not find that the fluoride levels in Sweden are harmful to the intelligence, says Mattias öhman, who is one of two researchers behind the study. Earlier research has shown that very high levels of fluoride are harmful to the health. Future studies should focus on finding at what levels this damage might occur. Our results indicate that these levels do, at any rate, exceed those we have in Swedish municipal drinking water.

Labour market outcomes?

The authors of the report were also interested in what happened on the labour market. They find that individuals who in their childhood and during their adolescence lived in areas with a higher level of fluoride seem to be employed to a somewhat larger extent at the age of 22-29 and have a somewhat higher labour income.

- That there is an income increase is a surprising result that we cannot really explain. It might be that good dental health is positive on the labour market says Mattias öhman.

Data and method

The study is based on information about the fluoride levels in the approximately 1700 municipal waterplants in Sweden. The study makes use of the fact that the fluoride levels vary between different waterplants and due to the individuals' moving patterns. Intelligence for men was measured in connection with the enlistment, while dental health, maths results, employment and income were measured for both men and women. The measurement period differs for different outcomes. Individuals born between the years 1985 and 1992 constitute the focus of the study. The individuals are followed until 2014.