While 49 studies have found an association between fluoride and IQ, the following seven studies did not find this association. Several points bear consideration about these studies:
First, a new study from New Zealand (Broadbent 2014) reports no association between fluoridation and IQ. As recognized by Dr. Philippe Grandjean, there are several glaring problems with this study, however, including the fact that there virtually all of the children in the “non-fluoridated” community used fluoride supplements (a prescription drug designed to deliver the same amount of fluoride a child would get from drinking fluoridated water). FAN discusses these problems here.
Second, the study by Calderon (2000) found that fluoride exposure was associated with other indices of neurotoxicity, including impaired visual-spatial organization.
Third, the study by Li (2010) did not compare a high fluoride area against a low-fluoride area. Instead, it compared the IQs of children with dental fluorosis in a high-fluoride area with the IQs of children without dental fluorosis in the same high-fluoride area.
Fourth, the study by Spittle (1998) of a fluoridated community in New Zealand made no attempt to ascertain the urinary fluoride levels of the children. This is particularly important to do in studies of western populations because there is now a great deal of overlap in fluoride exposures between children living in fluoridated vs. non-fluoridated communities. This overlap in exposure is due to several facts including: (1) frequent prescription of fluoride supplements to children in non-fluoridated areas; (2) ingestion of large amounts of fluoride toothpaste; (3) exposure to fluoridated water through processed foods and beverages; (4) exposure to fluoride through pesticides; and (5) exposure to fluoride from Teflon. Thus, any IQ study of western populations that does not include a measurement of individual fluoride exposure will be unlikely to find an association between fluoride and IQ.
Seven Studies finding no association between fluoride and IQ:
- Broadbent JM, et al. (2014). Community water fluoridation and intelligence: prospective study in New Zealand. American Journal of Public Health [Epub ahead of print, May 15]
- Kang J, et al. (2011). Effects of fluoride and arsenic in drinking water on children’s intelligence. Chinese Journal of School Health 32(6):679-81. [Chinese text]
- Li X, et al. (2010). Investigation and Analysis of Children’s IQ and Dental Fluorosis in a High Fluoride Area. Chinese Journal of Pest Control 26(3):230-31. [Translated from Chinese to English by FAN] [Chinese text |
- He M, Zhang C. (2010). Investigation of children’s intelligence quotient and dental fluorosis in drinking water-type of endemic fluorosis area in Pucheng county Shaanxi province before and after drinking water change. Chinese Journal of Epidemiology 29:547-48. [Article in Chinese]
- Calderon J, et al. (2000). Influence of fluoride exposure on reaction time and visuospatial organization in children. Epidemiology 11(4): S153.
- Spittle B, et al. (1998). Intelligence and fluoride exposure in New Zealand Children (abstract). Fluoride 31:S13.
- Hu Y, Yu Z. (1989). Research on the Intellectual Ability of 6-14 Year Old Students in an Area with Endemic Fluoride Poisoning. Collection of papers and abstracts of 4th China Fluoride Research Association. 6:73. [Translated from Chinese to English by FAN] [Chinese text]