Researchers at the University of Otago, New Zealand, disproved claims of poor mental health in children and adults due to fluoridated water.

For the study, the researchers tracked the health and development of over 1000 people born in Dunedin between 1972 and 1973 up to the age 38. They focused on the participant's exposure to fluoride during the first five years of their lives as this period is extremely crucial for development of the brain.

The researchers measured the average IQ score of the participants during ages 7-13 and also at age 38. They compared IQs of participants with and without access to fluoridated water, fluoride toothpaste and tablets.

The subtest scores of the participant's verbal comprehension, perceptual reasoning, working memory and processing speed were also taken into consideration. The researchers also looked into external factors linked to IQ variation like socio-economic status, birth weight and breastfeeding, and secondary and tertiary educational achievements.

The researchers collected data on IQ for 92 and 942 study members in childhood and adulthood, respectively.

"Our analysis showed no significant differences in IQ by fluoride exposure, even before controlling for the other factors that might influence scores. In line with other studies, we found breastfeeding was associated with higher child IQ, and this was regardless of whether children grew up in fluoridated or non-fluoridated areas," Lead author Dr Jonathan Broadbent said in a statement.

"Our findings will hopefully help to put another nail in the coffin of the complete canard that fluoridating water is somehow harmful to children's development. In reality, the total opposite is true, as it helps reduce the tooth decay blighting the childhood of far too many New Zealanders," Broadbent said.

Previous studies claimed that exposure to fluoride in water is deadly to the developing brain and can lead to IQ deficits. Otago researchers believe that these studies used poor research methodology and were largely biased.

The findings are published in the American Journal of Public Health.

According to the National Cancer Institute, nearly 60 percent of the Americans have access to fluoridated water through public water systems. Fluoride in water helps to prevent and reverse tooth decay. The optimal level of fluoride is 0.7 milligrams per liter of water.