Aug. 19, 2008 -- Exposure to arsenic, typically through drinking water, is linked to diabetes, according a study published in the Journal of the American Medical Association.
Thirteen million Americans -- and millions more worldwide -- are exposed to drinking water contaminated with more inorganic arsenic than the Environmental Protection Agency has deemed safe. The EPA standard is 10 micrograms per liter.
Researchers, led by Ana Navas-Acien, MD, PhD, of the Johns Hopkins Bloomberg School of Health, studied 788 adults who had their urine tested for arsenic exposure in the 2003-2004 National Health and Nutrition Examination Survey. Participants with type 2 diabetes had a 26% higher level of total arsenic in their urine than those without the disease. Levels of organic arsenic, called arsenobetaine, which is often found in seafood, were similar between two groups. Arsenobetaine is considered nontoxic.
After adjusting for diabetes risk factors and seafood intake, researchers found that participants in the top one-fifth of total urine arsenic levels (16.5 micrograms per liter) had 3.6 times the odds of having type 2 diabetes as those in the lowest one-fifth (3 micrograms per liter).
Researchers also looked at levels of dimethylarsinate, a compound created when inorganic arsenic is metabolized before excretion. Participants in the top one-fifth of urine dimethylarsinate levels (6 micrograms per liter) had 1.6 times the odds of having type 2 diabetes as those in the lowest one-fifth (2 micrograms per liter.)
There are several reasons that inorganic arsenic may contribute to diabetes. Insulin-sensitive cells that are exposed to insulin and sodium arsenic appear to take in less glucose than cells exposed only to insulin. Arsenic could influence genetic factors that interfere with insulin sensitivity and other processes. Arsenic also may contribute to oxygen-related cell damage, inflammation, and cell death, all of which are linked to diabetes.
The study adds more evidence that inorganic arsenic in drinking water is dangerous. Previous research has linked arsenic to cancer and other health problems.
"Given widespread exposure to inorganic arsenic from drinking water worldwide, elucidating the contribution of arsenic to the diabetes epidemic is a public health research priority with potential implications for the prevention and control of diabetes," the authors conclude.
An accompanying editorial written by Molly L. Kile, ScD, and David Christiani, MD, MPH, both of the Harvard School of Health, highlights the increasing prevalence of type 2 diabetes, which affects 7.8% of Americans (24 million individuals). Most research focus has been on prevention through medication and lifestyle changes, but additional research needs to be done on environmental factors, the authors write.
In the meantime, Kile and Christiani write, "It is prudent to minimize arsenic exposures while its effect on metabolic diseases continues to be researched."