The inhibition of mercury absorption by dietary ethanol in humans: cross-sectional and case-control studies

Background: Since the inhibition of mercury absorption by ethanol was serendipitously discovered in 1965,1 a limited number of small number studies with both animal and human subjects have reported results consistent with this finding. Aims: To investigate this phenomenon in a large scale human study with low level Hg exposed dentists. Methods: Data were collected for a sample of 1171 dentists, and both cross sectional and case-control methods were utilised to examine the data. Results: Abstainers (n = 345) had significantly higher urinary mercury concentrations (HgU) than drinkers (n = 826): 5.4 mug/l v 4.8 mug/l. Multiple linear regression showed a significant effect of ethanol dose on HgU after adjusting for potential confounders. A case-control analysis in which cases were defined as those individuals with urinary Hg concentrations of greater than or equal to15 mug/l (approximate to top 5%), and controls as those with concentrations of <1.0 mu g/l (approximate to bottom 5%), showed a clear protective dose-response relation; there was a decreasing risk of being a case (having an HgU >= 15 mu g/l) with increasing ethanol consumption. The significance of the adjusted model is p < 0.001, and the chi(2) test for trend across ethanol consumption categories in the adjusted model is p < 0.05, confirming the dose-response relation. Conclusion: We believe that this straightforward investigation provides the first specific confirmation in a large scale human study of the inhibitory effect of ethanol on urinary mercury concentration, and by inference, on mercury absorption.