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Researchers say fluoride in water is not neurotoxic, not harmful to IQ

Harold Mandel's picture
Refreshing drinking water

There has been a great deal of debate about the potential for fluorinated water to cause damage to the developing brains of children. Water fluoridation nevertheless continues to be a standard part of the water purification procedures in our communities. Recent research has shown that fluoride in water is not neurotoxic for people.

Researchers decided to confront the controversy surrounding water fluoridation by investigating the relationship which exists between community water fluoridation and IQ reported the American Journal of Public Health. A general population sample was used consisting of people born in Dunedin, New Zealand. Assessment was made as follows:

1: Residence in a community water fluoridation area

2: Use of fluoride dentifrice

3: Intake of 0.5-milligram fluoride tablets

IQ was assessed repeatedly between ages 7 to 13 years and at age 38 years.

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There were no significant differences found in IQ due to fluoride exposure. These findings run contrary to assertions that fluoride in the context of community water fluoridation programs is neurotoxic. The researchers concluded fluoridating water does not lower IQ reports the University of Otago in a review of this research.

This research from the University of Otago does not support the claims that fluoridating water negatively affects children’s mental development and adult IQ. The researchers were exploring the contentious claim that exposure to levels of fluoride which are used in community water fluoridation is toxic to the developing brain and can therefore result in IQ deficits.

Fluoride exposure during the 1st five years of life and IQ development

Lead author Dr Jonathan Broadbent has said this new research focused on fluoride exposure of participants during the first five years of their lives. These early years are a critical period in the development of the human brain. After this period the IQ has been seen to be relatively stable.

Dr Broadbent said this analysis showed there was not any significant difference in IQ by fluoride exposure even prior to controlling for the other factors which could influence scores. As seen in other studies the researchers found breastfeeding was associated with higher child IQ. The positive association with breastfeeding was seen regardless of whether kids grew up in fluoridated or non-fluoridated regions.

Review of Opponents' View on Fluoride in Water and IQ

Dr Broadbent says that studies that fluoridation opponents have said show that fluoride in water may cause IQ deficits have been reviewed. This research group says these studies relied on poor research methodology and have a high risk of bias. Dr Broadbent hopes these new findings will help to put an end to acceptance of allegations that fluoridating water is somehow harmful to children’s development.

This research is significant in view of the continued controversy surrounding fluoridating water. In consideration of the fact that fluoridating water helps reduce the tooth decay of children it is comforting to know this research upholds the safety of water fluoridation.



The NZ fluoride/IQ study is seriously flawed: Only about 10% of the kids Broadbent reviewed were from the non-fluoridated areas (99 out of 992). But 139 took fluoride tablets. Since fluoride tablets are recommended for children who don't live in fluoridated areas, it's safe to assume that most of the 99 were the ones who took the fluoride tablets. Broadbent doesn't provide the numbers. So Broadbent did not measure fluoride users against fluoride non-users. And he assumes that the kids in the fluoridated areas were drinking the tap water instead of bottled or tank water. And he failed to determine total fluoride intake from all sources. He provided no IQ analysis of children who consumed no fluoride. A different Dunedin study shows that kids who take fluoride tablets actually have higher rates of fluoride ingestion than kids who live in fluoridated areas. Broadbent also doesn't factor in the large amount of toothpaste toddlers studied ingest daily while brushing (once, twice or more times a day) because they can't or won't spit it out. Further Broadbent reports that critics of the Lancet fluoride/IQ studies didn't adjust for lead, iodine, arsenic, nutrition, and fluoride from other sources. But neither did he. Broadbent also based family income on occupation and got figures from a book - not on actual income of the family Broadbent is one of NZ’s leading political promoters of fluoridation. He is a dentist not developmental neurotoxicologist His article is obviously politically motivated, slanted and should be retracted. Broadbent's assertion that his study will put a nail in the coffin of fluoridation opposition is scientifically naive as over 100 animal studies and 38 human studies show a link to fluoride and brain deficits.