Fluoride Action Network

Fluoride & IQ: The 7 “No Effect” Studies

Fluoride Action Network | by Michael Connett | Updated April 2015

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: