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Please do not upvote this. If fluoride lowers IQ in children, then it would be difficult to reconcile the widespread use of fluoride (put in the water in many

Please do not upvote this. If fluoride lowers IQ in children, then it would be difficult to reconcile the widespread use of fluoride (put in the water in many developed nations since the mid 20th Century) with the Flynn Effect, so this really needs wide confirmation before anyone should take it seriously. http://en.wikipedia.org/wiki/Flynn_effect http://en.wikipedia.org/wiki/Flynn_effect

deevus 13y ago
Seems a little silly to bury it because you don't agree with it. I don't agree with it, but felt it was worth discussing here. I am interested in what other HNers have to say.
- dalke 13y ago
  The HuffPo article gives a false distortion of what the research study actually says. That's why it should be buried. The article says "Despite the evidence against it, fluoride is still added to 70 percent of U.S. public drinking water supplies." While the study reports a negative correlation with higher fluoride levels, "high" in the underlying studies usually mean above 2mg/L. The US recommended levels are (as the study says) between 0.7 and 1.2 mg/L. A city which adds fluoride to get to 0.7mg/L is in the "low" category for the study, where the IQ levels are higher. As the study did not analyze negative effects of levels lower than about 1.0mg/L, it's impossible to use it to conclude that a level of 0.7mg/L, even if reached by adding fluoride, is bad for IQ. But the HuffPo article makes that conclusion anyway.
nabla9 13y ago
high levels of fluoride <> fluoride added to water. Recommended upper levels of fluoride are <1.0 mg/L. Typical naturally occurring levels are 0.4 mg/L. In many areas that get water from mountains (India, China, western USA) naturally occurring fluoride can be anything from 1.5 mg/L to 50 mg/L. If you are American living in the west coast and use water from your own well, you might want to check your fluoride levels. Excess fluoride is removed from tap water in US.
- dalke 13y ago
  While the Huffington Post article is fully of scary alarmism, the actual referenced paper, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491930/pdf/ehp.1104912.pdf http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491930/pdf/ehp.... , is in complete agreement with what you just wrote. Some relevant quotes: > Opportunities for epidemiological studies depend on the existence of comparable population groups exposed to different levels of fluoride from drinking water. Such circumstances are difficult to find in many industrialized countries, because fluoride concentrations in community water are usually no higher than 1 mg/L, even when fluoride is added to water supplies as a public health measure to reduce tooth decay. Multiple epidemiological studies of developmental fluoride neurotoxicity were conducted in China because of the high fluoride concentrations that are substantially above 1 mg/L. Table 1 lists the results, and quantify more of what "high" and "low" mean. In all but one case, "high" is above 1mg/L (and mostly over 2mg/L) and "low" is under 1mg/L. (The one case, Xiang et al. 2003, uses "0.57–4.5 mg/L (high); 0.18–0.76 mg/L (reference)", so the high range is mostly above 1mg/L). These results explain why the US is thinking to lower recommended fluoridation levels in the US: > In response to the recommendation of the NRC (2006), the U.S. Department of Health and Human Services (DHHS) and the U.S. EPA recently announced that DHHS is proposing to change the recommended level of fluoride in drinking water to 0.7 mg/L from the currently recommended range of 0.7–1.2 mg/L, and the U.S. EPA is reviewing the maximum amount of fluoride allowed in drinking water, which currently is set at 4.0 mg/L (U.S. EPA 2011). Therefore, while the HuffPo article implies that any fluoridation is harmful, the paper itself considers most US municipal water supplies - at least, those with <1mg/L - to be in the "low" category that is better for higher IQ. What about lower fluoridation levels? From the paper: > A recent cross-sectional study based on individual-level measure of exposures suggested that low levels of water fluoride (range, 0.24–2.84 mg/L) had significant negative associations with children’s intelligence (Ding et al. 2011). However, that's a different type of study, so the authors excluded it from this metadata analysis.
lotsofmangos 13y ago
Your point actually supports the opposite of your position. The Flynn effect was much more marked in Europe than it was in the US and fluoridation is much less widespread in Europe than in the US. http://www.iqcomparisonsite.com/Locations.aspx http://www.iqcomparisonsite.com/Locations.aspx http://en.wikipedia.org/wiki/Fluoridation_by_country#Europe http://en.wikipedia.org/wiki/Fluoridation_by_country#Europe

deevus 13y ago

Seems a little silly to bury it because you don't agree with it. I don't agree with it, but felt it was worth discussing here. I am interested in what other HNers have to say.

dalke 13y ago
The HuffPo article gives a false distortion of what the research study actually says. That's why it should be buried. The article says "Despite the evidence against it, fluoride is still added to 70 percent of U.S. public drinking water supplies." While the study reports a negative correlation with higher fluoride levels, "high" in the underlying studies usually mean above 2mg/L. The US recommended levels are (as the study says) between 0.7 and 1.2 mg/L. A city which adds fluoride to get to 0.7mg/L is in the "low" category for the study, where the IQ levels are higher. As the study did not analyze negative effects of levels lower than about 1.0mg/L, it's impossible to use it to conclude that a level of 0.7mg/L, even if reached by adding fluoride, is bad for IQ. But the HuffPo article makes that conclusion anyway.

nabla9 13y ago

high levels of fluoride <> fluoride added to water. Recommended upper levels of fluoride are <1.0 mg/L. Typical naturally occurring levels are 0.4 mg/L. In many areas that get water from mountains (India, China, western USA) naturally occurring fluoride can be anything from 1.5 mg/L to 50 mg/L. If you are American living in the west coast and use water from your own well, you might want to check your fluoride levels. Excess fluoride is removed from tap water in US.

dalke 13y ago
While the Huffington Post article is fully of scary alarmism, the actual referenced paper, at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491930/pdf/ehp.1104912.pdf http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491930/pdf/ehp.... , is in complete agreement with what you just wrote. Some relevant quotes: > Opportunities for epidemiological studies depend on the existence of comparable population groups exposed to different levels of fluoride from drinking water. Such circumstances are difficult to find in many industrialized countries, because fluoride concentrations in community water are usually no higher than 1 mg/L, even when fluoride is added to water supplies as a public health measure to reduce tooth decay. Multiple epidemiological studies of developmental fluoride neurotoxicity were conducted in China because of the high fluoride concentrations that are substantially above 1 mg/L. Table 1 lists the results, and quantify more of what "high" and "low" mean. In all but one case, "high" is above 1mg/L (and mostly over 2mg/L) and "low" is under 1mg/L. (The one case, Xiang et al. 2003, uses "0.57–4.5 mg/L (high); 0.18–0.76 mg/L (reference)", so the high range is mostly above 1mg/L). These results explain why the US is thinking to lower recommended fluoridation levels in the US: > In response to the recommendation of the NRC (2006), the U.S. Department of Health and Human Services (DHHS) and the U.S. EPA recently announced that DHHS is proposing to change the recommended level of fluoride in drinking water to 0.7 mg/L from the currently recommended range of 0.7–1.2 mg/L, and the U.S. EPA is reviewing the maximum amount of fluoride allowed in drinking water, which currently is set at 4.0 mg/L (U.S. EPA 2011). Therefore, while the HuffPo article implies that any fluoridation is harmful, the paper itself considers most US municipal water supplies - at least, those with <1mg/L - to be in the "low" category that is better for higher IQ. What about lower fluoridation levels? From the paper: > A recent cross-sectional study based on individual-level measure of exposures suggested that low levels of water fluoride (range, 0.24–2.84 mg/L) had significant negative associations with children’s intelligence (Ding et al. 2011). However, that's a different type of study, so the authors excluded it from this metadata analysis.

lotsofmangos 13y ago

Your point actually supports the opposite of your position. The Flynn effect was much more marked in Europe than it was in the US and fluoridation is much less widespread in Europe than in the US. http://www.iqcomparisonsite.com/Locations.aspx http://www.iqcomparisonsite.com/Locations.aspx http://en.wikipedia.org/wiki/Fluoridation_by_country#Europe http://en.wikipedia.org/wiki/Fluoridation_by_country#Europe