We've long known that aspects of modern life — eating sugary foods or sitting for long stretches in front of the tv or steering wheel, for example — contribute to diabetes.
But evidence is mounting that another facet of contemporary life—routine exposure to endocrine-disrupting chemicals—could be worsening the diabetes epidemic. In a review article out last month in Advances in Pharmacology, researchers say it's vital that doctors and policymakers take environmental health into account as they seek to stem the global rise in diabetes.
"We often attribute patient's disease risk to individual choices, and we don't necessarily think about how systems and environments play into disease risk," Dr. Robert Sargis, lead author and an endocrinologist at the University of Illinois at Chicago, told EHN.
The new review article surveyed more than 200 animal, cell, clinical, and epidemiological studies, finding that exposure to endocrine disruptors is a "novel but under-appreciated" diabetes risk factor.
Global uptick in diabetes
Diabetes has been on the rise globally — in 1980, 108 million people around the world had diabetes; now, more than 420 million people have the disease, according to the World Health Organization. While type 1 diabetes is an autoimmune disease that occurs when our bodies don't produce enough insulin, more common type 2 diabetes occurs when we develop resistance to insulin, a hormone produced by the pancreas that helps us convert sugar into energy.
Obesity, which has tripled around the world since 1975, is a main risk factor in developing type 2 diabetes.
Dr. Carolina Solis-Herrera, assistant professor of Medicine in the Division of Diabetes at the University of Texas Health at San Antonio, told EHN that family history is another risk. "If one of your parents has type 2 diabetes, your risk of developing diabetes over time is about 30 percent," she said. "And if both of your parents have type 2 diabetes, your risk can go up to 60 percent." Other conditions — like heart disease, high cholesterol, hypertension and polycystic ovary syndrome — can also put someone more at risk for developing diabetes.
The authors of the new review say that while calorie-rich diets, lack of exercise, sleeping issues, and genetic risk factors clearly play a major role in the diabetes epidemic, those factors fail to fully account for "the dramatic rise and spread" of diabetes.
How endocrine disruptors contribute to diabetes
Over the past couple of decades, researchers have examined what role endocrine disruptors —chemicals that impact our bodies' hormone making system — have on diabetes. We come in contact with endocrine disruptors in items like receipts, contaminated food, and cosmetics, as well as by breathing in air pollution. Researchers have found, according to Sargis, that certain endocrine disruptors such as PCBs, arsenic, and DDT can impair our ability to make insulin, make us more insulin-resistant, and, in some cases, do both. Some endocrine disruptors, like BPA, have also been linked to obesity.
Dr. Ángel Nadal Navajas, a professor of physiology at the Miguel Hernandez University of Elche in Spain who was not involved with the study, told EHN endocrine disruptors alone don't cause diabetes "but exposure to endocrine disruptors increases (one's) probability of developing type two diabetes. It's one more factor, and for some people, it's going to be a major factor."
There have been extensive human studies linking BPA, a compound used in plastics and canned food lines that mimics estrogen hormones, to diabetes. "I don't think there is any doubt the connection is there," said Nadal Navajas.
There have also been epidemiological studies showing associations between diabetes and exposure to arsenic, organochlorine pesticides, air pollution, and other endocrine disruptors, according to the review. While some of endocrine disruptors looked at, like DDT, have been banned, they don't break down readily in the environment or in our bodies. The authors call for more research into how endocrine disruptors could affect type 1 and gestational diabetes, which occurs when glucose levels rise during pregnancy and puts both mother and child at a greater risk for type 2 diabetes.
In the U.S., Indigenous, Latinx, and Black people have a greater risk of developing diabetes, and of suffering complications from the disease. Some of these populations are also exposed to more to endocrine disruptors from air pollution and other sources because of where they live and what they do for work.
While this disproportionate exposure could be contributing to the higher levels of diabetes in these communities, it's difficult to tease out the link "because people who are exposed to endocrine-disrupting chemicals are also probably the same ones who have limited access to healthy food and limited access to health care," Dr. Lisa Goldman Rosas, an assistant professor of epidemiology and population health at Stanford University, told EHN.
Environmental health training and oversight
With new chemicals coming out all the time with limited federal oversight, Sargis and Nadal Navajas both said we need to come up with better ways to test chemical safety en masse. Europe has already started doing that with a recent project to develop better ways to test the hormone-disrupting effects of new chemicals before they come onto the market.
In the meantime, doctors, and the medical schools that train them, need to better take into account environmental health components that could put patients at risk for developing diabetes, or influence their disease trajectory, said Sargis.
"We (tend to) approach medicine as a one-on-one relationship with the patient and the physician, and that sort of neglects these external factors," he said, adding that this was in part because physicians have limited environmental health training.
Banner photo credit: National Human Genome Research Institute
