Practicing the same method as geneticists use to study genetic factors for disease, researchers at Stanford University successfully used an environment-wide association study (EWAS) to study environmental factors for disease. The report appeared in the May 20 issue of PLoS, a journal of The Public Library of Science.
The researchers turned to EWAS as a way to study environmental risk factors because genetic-wide association studies have been so effective in recognizing genetic risk factors, says Atul Butte, researcher and assistant professor of pediatrics and medical informatics at Stanford University.
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"Environmental factors haven't gotten the same kind of respect that the genetics field has," he says, pointing out that environmental factors are much stronger in affecting the development of Type 2 diabetes. "Environmental causes are certainly stronger. We wouldn't have the increase rate of Type 2 diabetes [that we do] from genetics because our genes aren't changing fast enough."
Butte and his team focused on Type 2 diabetes, which is a "public health menace," he says.
The scientists gathered public data from the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey, which looked at environmental risk factors such as nutrients, vitamins, allergens, pollutants and pesticides.
The data was all adjusted to account for factors including age, gender, body mass index and socioeconomic status.
Out of 226 environmental factors, the researchers found Type 2 diabetes association with tocopherol, a form of vitamin E, heptachlor epoxide, a pesticide that was outlawed in the 1980s, and polychlorinated biphenyls (PCBs), which are chemicals that were banned in the 1970s because of their association with cancer.
Edward McCabe, past president of American Society of Human Genetics and current physician-in-chief at Mattel Children's Hospital at UCLA, says the fact that the researchers were able to study 226 factors is "impressive."
Butte says he was "absolutely" surprised by the findings, especially the vitamin E association with Type 2 diabetes.
The researchers were also able to confirm that vitamin D and beta carotene possess protective properties. And they didn't even look at some factors, which have been proven as having an effect on Type 2 diabetes development.
"The most obvious factors are still always diet and exercise," Butte says. "What you eat still plays the largest role [in developing Type 2 diabetes]. We knew we would find some of those, so we didn't even look at those...This doesn't mean all of a sudden you can stop that diet or stop trying to lose weight."