Toxic Chemicals and Diabetes

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Diabetes epidemics have followed the standard American diet across the world. The starches, sugars, and saturated fats in mass-produced foods would seem to be the cause. But maybe not. There are other nasty things in those packages.

Last week I attended the American Public Health Association (APHA) conference in San Francisco, and learned some things you might want to know. The most striking was the effect of environmental chemicals in the development of diabetes.

In my book, Diabetes: Sugar-Coated Crisis, I correctly called diabetes an environmental illness. But I mostly meant an environment of high stress, junk food, and few opportunities to move our bodies. I mentioned air and water pollution, but didn’t stress them.

Since then, much new research shows that environmental chemicals have a great deal to do with both diabetes and obesity. I learned much of this news from Sarah Howard, MS, National Coordinator of the Collaborative on Health and the Environment’s (CHE) working group on diabetes and obesity. Here is her Web site on diabetes.

This week we’ll look at chemicals and Type 2. Next week, I’ll write about Type 1.

Categories of pollutants that have been associated with Type 2 diabetes include the following:

Persistent organic pollutants (POPs): A 2006 study found that US adults with the highest exposure to six kinds of POPs had 37.7 times the risk of diabetes of people with the lowest levels of exposure. You read that right, 37.7 times more diabetes! The POPs included dioxins, DDE, oxychlordane, and trans-nonachlor. The last two are breakdown products of the pesticide chlordane.

Virtually everyone in the modern world is contaminated with POPs. They were sprayed on most commercially grown foods in America and have many industrial uses. But the more you can avoid them, the better. You can find them lurking in animal fats. POPs and arsenic are the chemicals most strongly linked with diabetes by existing evidence.

According to a 2006 article in Diabetes Care, obesity did not increase the risk of Type 2 diabetes in obese people with very low levels of POPs in their bodies. An editorial by a Spanish doctor in The Lancet in 2006 stated, “This finding would imply that virtually all the risk of diabetes conferred by obesity is attributable to persistent organic pollutants, and that obesity is only a vehicle for such chemicals. This possibility is shocking.”

POPs may do damage by disrupting hormone function or altering gene expression (function.)

Air pollutants: Studies in the USA, Canada, and Germany, among several other countries, have found that women and children exposed to higher levels of traffic-based air pollution had much higher rates of Type 2 diabetes. The pollutants most studied were nitrogen dioxide and “particulate matter,” the tiny grains put in the air from soot and tailpipe exhaust.

A study of Iranian children aged 10–18 found that children exposed to higher levels of air pollution had increased insulin resistance. Mice exposed to particulate matter in early life developed signs of increased insulin resistance, fat formation, and inflammation in adulthood, even when fed a normal diet.

Chinese scientists found that particulate air pollution actually changed DNA in mouse mitochondria. The process leading from air pollution to insulin resistance is thought to involve oxidative stress from the free radicals in the pollution.

Pesticides: Farm workers have high rates of Type 2 diabetes. One study found that women who mixed or applied pesticides to crops or repaired pesticide application equipment during the first trimester of pregnancy had a higher risk of developing gestational diabetes. Four herbicides and three insecticides were found to increase risk.

Phthalates (pronounced “thalates”) are chemicals used in plastic manufacture and in cosmetics, perfumes, and industrial paints and solvents. DEHP is the most commonly used phthalate, used to manufacture a variety of products, including food packaging and medical devices. It can enter people’s bodies by leaching out of these products.

Studies in Sweden and Mexico found high levels of phthalate chemicals in elderly people with diabetes. These chemicals were linked to impaired insulin production and increased insulin resistance.

Rats given the phthalate DEHP developed symptoms of diabetes (mainly high blood glucose). The symptoms went away when the phthalates were stopped.

Phthalates may cause diabetes and obesity by disrupting hormone function — they seem to promote the growth of some hormone receptors and suppress others, and stimulate fat cell growth.

Selenium is not an industrial chemical. It’s a vital trace mineral, but too much selenium has been associated with Type 2 diabetes in some studies of people in the US. One study found that in 900 US adults exposed to high selenium levels, the prevalence of diabetes increased with increasing levels of selenium.

Many people take selenium supplements, but a randomized, double-blind, placebo-controlled study found that selenium supplementation may increase the risk of developing Type 2 diabetes. The mechanism is thought to be oxidative stress leading to insulin resistance.

Other chemicals have been implicated in Type 2, with varying degrees of evidence. These include flame retardants, such as polybrominated diphenyl ethers (PBDEs), arsenic (which is present in some drinking water), bisphenol A (BPA), and radiation. Still others may be implicated in Type 1, as we’ll discuss next week.

To learn more, please visit the Web site of Diabetes and the Environment. It’s a great site and organization.

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