Over the past decade, there has been a steady drumbeat of press warning of the risks from drinking bottled water. The idea — kept alive by press releases from dental associations — is that because most bottled waters have low levels of fluoride, people switching from tap water (which is usually fluoridated) to bottled water will not receive a sufficient intake of fluoride to ward off tooth decay.
One of the things that has been absent in the discussion about bottled water’s “threat” to teeth, is the lack of empirical evidence to justify the claim. It was a significant development this year, therefore, when researchers from the NIH-funded “Iowa Fluoride Study” published a study which provides some actual hard data on the issue (8). [See also this previous Australian study.]
For the past decade, these researchers have been carefully monitoring the fluoride intake of hundreds of Iowan children, from birth through adolescence. From this group of children, the researchers separated out those children who regularly used bottled water. They then compared the tooth decay history of these bottled water drinkers with children who regularly drank tap water (most of which was fluoridated). Even when controlling for important variables, such as socioeconomic status and toothbrushing frequency, the authors found no relationship between bottled water use and tooth decay (in baby or permanent teeth), even though the fluoride intake of the bottled water users was significantly lower than the tap-water users. Similar findings were reported in the Australian study.
According to the Iowa study:
“Presumably, such reduced exposure to fluoride would result in increased caries occurrence. However, the present study did not find any significant differences in caries prevalence or incidence between bottled water users and those who did not use much bottled water.”
Due to the limited number of bottled-water users identified in this group of Iowan children, however, the authors recommend that larger studies be conducted in order to reach more definitive conclusions. The prior Australian study, however, had a very large scale (13,000) and yet it still found no relationship between consumption of “non-public” water and tooth decay in the permanent teeth.
Broffitt B, et al. (2007). An investigation of bottled water use and caries in the mixed dentition. Journal of Public Health Dentistry 67(3):151-8.