Firstly, key points from the NIH website page on fluoridation facts;
- Fluoride in water helps to prevent and can even reverse tooth decay.
- More than 60 percent of the U.S. population has access to fluoridated water through public water supply systems.
- The optimal level of fluoride to prevent tooth decay is 0.7 milligrams per liter of water.
- Many studies, in both humans and animals, have shown no association between fluoridated water and cancer risk.
It seems strange that, if the NIH funded a study which stated otherwise, the NIH would continue to conclude a contrary position. How can the anti-fluoridation advocate hold the NIH up as authority and yet ignore the actual conclusions drawn by the NIH?
Taking further effort to look through the various anti-fluoridation websites, to find the actual study this claim refers to (as most of the time, it is stated without citation) I found that it comes from an ongoing study commonly known as the “Iowa Fluoride Study“.
FAN put it this way;
“In 2009, the Iowa researchers published the long-awaited data on the effect of total fluoride exposure on tooth health after 9 years of the children’s life. Much to the disappointment of fluoridation advocates, fluoride intake was found to be significantly associated with dental fluorosis, but not tooth decay.”
The study they refer to is, Warren et al (2009) Considerations on Optimal Fluoride Intake Using Dental Fluorosis and Dental Caries Outcomes – A Longitudinal Study, and, as is usually the case, on actual inspection, the article itself reads a little differently to the cherry picked and re-quoted article provided by FAN.
In essence, the study attempts, as the title suggests, to find the “optimal” fluoride intake value. The results of their study basically conclude that this is a difficult thing to achieve, to say the least, if not entirely impossible.
However, they do not conclude there is no significant association with fluoride intake and caries prevention. Rather, they find an overlap; with lower fluoride exposure, there is lower rates of fluorosis and with higher fluoride exposure, less caries.
Yet, as with Bassin et al (2006), here too the researchers stress limitations with the study and caution in interpreting the results – something the average anti-fluoridation advocate often fails to mention. Limitations include; actual control of fluoride intake – some sources were not accounted for; the study sample was not representative of any defined population; and, the vast majority of fluorosis was mild or very mild (only 3% were considered severe) and not of aesthetic concern – results that mirror those of the 2007 NSW Dental Health Survey discussed above.
From the closing paragraph of Warren et al (2009);
“Despite the limitations, the study provides the only recent, outcome-based assessment of the “optimal” fluoride intake, and as such, it appears that while the generally accepted range of 0.05 to 0.07 mg F/kg bw may still be associated with caries prevention, it may not be optimal in preventing fluorosis.”
“By the same token, while limiting fluoride intake to less than 0.05 mg F/kg bw may be appropriate to prevent fluorosis, given that most fluorosis were mild even at higher intake levels, recommendations to limit fluoride intake to less than 0.05 mg F/kg bw may not be justified.”
Rather than being the “final word” on the matter of fluoridation, Warren et al (2009) concludes that fluoride intake is not, as the anti-fluoridation advocate would like their readers to otherwise believe, a black and white scenario. There is certainly benefit in the use of fluoride for caries prevention as well as evidence of increased fluorosis with higher rates of exposure, even if in most cases very mild to mild.
FAN also refer to two more recent papers from the same research group; Chankanka et al (2011) Longitudinal associations between children’s dental caries and risk factors and Chankanka et al (2011) Mixed Dentition Cavitated Caries Incidence and Dietary Intake Frequencies.
The former admits to a study sample of mostly white individuals with a generally middle to higher socio-economic status, which typically results in greater oral health management (more than 99% used fluoridated tooth paste, which anti-fluoridation groups insist is swallowed).
The latter is only listed in the references and is not actually cited in the article itself. Again, this is the same sample group and both studies are primarily focused upon oral hygiene and what food and drink the individuals consume. Both suffer the same limitations when analysing the effectiveness of water fluoridation due to other social factors and the cohort itself (primarily “well off” Caucasians).
The U.S. NIH continues to support the use of fluoride because they have sufficient technical scientific training to actually read and interpret the relevant research. The Iowa Fluoride Study has not concluded that water fluoridation is ineffective. It has simply shown, through many studies over the years, that the relationship is indeed complex and that strategies for caries prevention must include a wide range of actions, which still includes fluoride.