Water fluoridation prevents dental cavities, which are a costly public health concern. But despite the benefits supplemental water fluoridation remains a controversial subject. Some indicate it may cause long term health problems, but studies reporting side effects have been minimal or inconclusive. The long-term effects of ingested fluoride remain unclear.
A recent study published in the Journal of Water and Health examined links between water fluoridation and diabetes. Type 2 diabetes is a growing epidemic in the United States. Incidence rates have nearly quadrupled in the past 32 years and show no signs of stopping. According to the study, fluoridation with sodium fluoride could be a contributing factor to diabetes rates in the United States, as the chemical is a known preservative of blood glucose.
The sole author of the paper, Kyle Fluegge, Ph.D., performed the study as a post-doctoral fellow in the Department of Epidemiology and Biostatistics at Case Western Reserve University School of Medicine. Fluegge now serves as health economist in the Division of Disease Control for the New York City Department of Health and Mental Hygiene and co-director of the Institute of Health and Environmental Research in Cleveland, Ohio.
In the study, Fluegge used mathematical models to analyze publicly available data on fluoride water levels and diabetes incidence and prevalence rates across 22 states. He also included adjustments for obesity and physical inactivity collected from national telephone surveys to help rule out confounding factors. Two sets of regression analyses suggested that supplemental water fluoridation was significantly associated with increases in diabetes between 2005 and 2010.
“The models look at the outcomes of [diabetes] incidence and prevalence being predicted by both natural and added fluoride,” said Fluegge.
Fluegge reported that a one milligram increase in average county fluoride levels predicted a 0.17 percent increase in age-adjusted diabetes prevalence. Digging deeper revealed differences between the types of fluoride additives used by each region. The additives linked to diabetes in the analyses included sodium fluoride and sodium fluorosilicate. Fluorosilicic acid seemed to have an opposing effect and was associated with decreases in diabetes incidence and prevalence. Counties that relied on naturally occurring fluoride in their water and did not supplement with fluoride additives also had lower diabetes rates.
The positive association between fluoridation and diabetes was discovered when Fluegge adjusted fluoride exposure levels to account for estimated per capita tap water consumption.