One of the myths promoted by the anti-fluoride people is that fluoridation is bad for our bones. As with similar myths the evidence used to support the claims usually comes from studies of situations where people have high F intake, often from natural sources.
However, there are studies which anti-fluoridationists can quote which do relate to fluoridated water concentrations. For example, this is one of the many claims made by Christopher Bryson in his book The Fluoride Deception. This book tends to be used as scripture by anti-fluoridationists today so I thought I would look a bit more deeply into his claim.
Such deeper looks can often show problems of confirmation bias or uncritical evaluation of the literature – it did in this case.
Bryson based his claim solely on work by Joseph Lyon, in particular the paper Hip Fractures and Fluoridation in Utah’s Elderly Population by Christa Danielson; Joseph L. Lyon; Marlene Egger; and Gerald K. Goodenough (1992). However, he does claim “subsequent studies have found similar associations between fluoride in water and bone fractures.”
Danielson et al. concluded:
“We found a small but significant increase in the risk of hip fracture in both men and women exposed to artificial fluoridation at 1 ppm, suggesting that low levels of fluoride may increase the risk of hip fracture in the elderly”
Well, it doesn’t take much searching to find papers with contrary conclusions. For example Community water fluoridation, bone mineral density, and fractures: prospective study of effects in older women by
Kathy R Phipps, Eric S Orwoll, Jill D Mason, Jane A Cauley (2000).
“Long term exposure to fluoridated drinking water does not increase the risk of fracture.”
So different conclusions, but why? Well Phipps et al. allude to the causes of contradictory conclusions in their introduction.
“While the benefit of fluoridation in the prevention of dental caries has been overwhelmingly substantiated, the effect of fluoridation on bone mineral density and rates of fracture is inconsistent. Ecological studies that compare rates of fracture specific for age and sex between fluoridated and nonfluoridated communities have variously found that exposure to fluoridated water increases the risk of hip fracture, (here they refer to Danielson et al 1992) increases the risk of proximal humerus and distal forearm fracture, has no effect on fracture risk, and decreases the risk of hip fracture. Ecological studies, however, have a major design flaw—they are based on community level data and cannot control for confounding variables at the individual level.” (My emphasis).
“We determined, on an individual level, whether older women with long term exposure to fluoridated water had different bone mass and rates of fracture compared with women with no exposure.” (My emphasis).
And they concluded:
“This is the first prospective study with adequate power to examine the risk of specific fractures associated with fluoride on an individual rather than a community basis. Our results show that long term exposure to fluoridation may reduce the risk of fractures of the hip and vertebrae in older white women. Because the burden of osteoporosis is largely due to fractures of the hip, this finding may have enormous importance for public health. If fluoridation does reduce the risk of hip fracture it may be one of the most cost effective methods for reducing the incidence of fractures related to osteoporosis. In addition, our results support the safety of fluoridation as a public health measure for the control of dental caries.”
So, if we compare the results from the two studies we see that while Danielson et al (1992) reported an increase in the risk of hip fracture for women drinking fluoridated water, Phipps et al (2000) actually reported a decrease in the risk. The difference being that Phipps et al (2000) removed confounding factors such as medical history, drugs and supplements, reproductive history, menopause, alcohol consumption, exercise, smoking, caffeine intake, height and weight.
While preparing this I noted a new paper on this subject just published – Näsman et al (2013) “Estimated Drinking Water Fluoride Exposure and Risk of Hip Fracture:A Cohort Study
The abstract reports:
“Estimated individual drinking water fluoride exposure was stratified into 4 categories: very low, < 0.3 mg/L; low, 0.3 to 0.69 mg/L; medium, 0.7 to 1.49 mg/L; and high, ≥ 1.5 mg/L. Overall, we found no association between chronic fluoride exposure and the occurrence of hip fracture. . . . fluoride exposure from drinking water does not seem to have any important effects on the risk of hip fracture, in the investigated exposure range.”
So extra support for the conclusion that fluoridation does not lead to increased risk of hip fracture.
Motivated cherry picking
I think this shows the danger of cherry picking studies to support a preconceived position. And of relying on individual sources, or ideologically motivated sources like The Fluoride Deception, for information.
There is a large amount of research on fluoride which to the uninitiated must seem contradictory. Proper review of this literature requires skills in critical thinking, and background in the field. The sort of thing that activist groups, and local body councils, don’t have.
Of course, I have no special background in this area either – and I don’t pretend that my summary here is at all definitive. However, it does show how misinformation can easily be promoted, with an apparent respectability conferred by scientific references, when motivated people cherry pick.