An interesting article titled “Community Water Fluoridation and Intelligence: Prospective Study in New Zealand,” appears in the 2014 edition of the American Journal of Public Health by Jonathan M. Broadbent and et. al. The researchers set out to explore whether or not having fluoride in water that one drinks when they are young and age effects the developing brain negatively. The researchers followed nearly all aspects of the health and development of around 1,000 people born in Dunedin in southeast New Zealand in 1972-1973, up to age 38.
The researchers compared IQs of those who grew up in Dunedin suburbs with and without fluoridated water. Furthermore, if one used fluoride toothpaste and tablets the researchers used this in their analysis. The researchers focused on fluoride expose during the first five years of life as this is a critical period of time in brain development.
The researchers looked at average IQ scores between the ages of 7 and 13 years and at age 38, along with subtest scores for working memory, verbal comprehension, perceptual reasoning, and processing speed. A total of 992 child and 942 adults had data available.
The researchers were sure to control for childhood factors which are known to be associated with variation in IQ including socioeconomic status, breastfeeding, birth weight, and educational achievement.
The researchers feel that no significant difference in IQ was found when accounting for fluoride exposure while controlling for other potential IQ factors. The researchers found that breastfeeding was associated with higher child IQ regardless of fluoridation. The researchers feel those fluoridation opponents who show that fluoride in water can cause IQ problems often have poor methodology in their research and have bias. The researchers feel the Dunedin Multidisciplinary Study for which their data came from is of high quality and world renowned. The researchers do note that fluoride in water does help reduce tooth decay in childhood in New Zealanders.