Interpreting the Newcastle fluoride bioavailability study

doi:10.1136/bmj.39374.404502.BE

BMJ 2007;335:840-841 (27 October), doi:10.1136/bmj.39374.404502.BE

Letters

Fluoridation

Interpreting the Newcastle fluoride bioavailability study

The first 150 words of the full text of this article appear below.

We are surprised that the chief dental officer and chief medicalofficer for England in their full response to Cheng et al considerthat the Newcastle study on bioavailability "contributed toa better understanding of the health effects of water fluoridation."¹² The researchers themselves urged caution when interpretingthe results.³ It is disappointing that such senior public healthofficials make the error of assuming that "no statisticallysignificant differences in bioavailability between artificiallyand naturally fluoridated water" has any meaning when the studywas too small to find scientifically important differences.

Interestingly, despite the small size, the Newcastle study didreport a significant difference in the relative bioavailabilityof fluoride in drinking water (plasma Fp%) at three hours (27%)and eight hours (36%) follow-up (mean difference in Fp% (0-8)=35,95% confidence interval 5.9 to 64.5).³ However, the authorsremoved one of the 20 data points, which they determined wasan . . . [Full text of this article]

Stephen T Holgate, MRC clinical professor of immunopharmacology¹, Trevor A Sheldon, professor and pro-vice chancellor²

¹ IIR Division, Southampton General Hospital, Southampton SO16 6YD, ² Health Services Research, University of York, York YO10 5DD

sth@soton.ac.uk