Pollution and Diabetes

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In response to my blog post on thin Type 2s, Robinhood wrote, “According to the Veteran’s Administration, [my type 2] was brought on by exposure to Agent Orange.” The VA could be right. Chemical pollution may be a major cause of both Type 1 and Type 2 diabetes.

We think of pollution as causing cancer, maybe, or birth defects. How could pollution of air or water cause diabetes? Isn’t that just about genes and weight if you’re Type 2, or about genes, viruses, and bad luck if you’re Type 1?

Apparently not. A 2006 study of children in Southern California found that those exposed to ozone, sulfates, or cigarette smoke in early childhood were two to three times more likely to develop Type 1 diabetes. Meanwhile, a reported published in July 2009 on Great Lakes fishermen found “consistent, dose-related associations of DDE” [a breakdown product of the pesticide DDT] with diabetes. The DDE is probably being consumed from fish caught in the Lakes’ polluted waters.

Writing in 2008 in the Lancet, one of the world’s leading medical journals, Oliver Jones, PhD, and Julian Griffin, PhD, called for more research into the link between persistent organic pollutants (POPs) and insulin resistance. POPs include Agent Orange, DDT, and other industrial and agricultural chemicals.

Pollution can get into our bodies from food, water, or the air we breathe. A 2002 study by Alan Lockwood, MD, at the University of Buffalo ranked the 50 American states by air pollution levels and diabetes levels. States with more pollution consistently have more diabetes. The government source for the pollution levels by states did not even include dioxins (a type of poisonous chemical), so the real correlation might be even stronger than Lockwood found.

Korean studies found a very strong association between POPs and diabetes. Interestingly, the Korean scientists found that the usual association between obesity and diabetes disappeared in people with low concentrations of POPs in their blood. Could it be that it’s the pollution, not the weight, that causes diabetes? Or could pollutants be causing both the weight AND the diabetes?

Sanjay Rajagopalan, MD, at Ohio State University found that mice who were exposed to polluted air developed inflammation, insulin resistance, and increased body fat. The effects were worse when combined with a poor diet.

“It’s interesting that the diabetic increases have been most notable in urbanized areas, where there’s been a high percentage of patients being exposed to bad air,” says Dr. Rajagopalan.

How could this be?
So here are all these strong associations between pollution and diabetes. You can also associate diabetes with high weight, low income, poor education, and many other factors. So what? Two things can be seen together; that doesn’t mean one causes the other. Before we can talk about pollution causing diabetes, we would have to have some idea how this could happen. Scientists have been looking into that, too.

A report from the National Academy of Sciences (NAS) in 2000 cited several reasons to think that chemicals like Agent Orange really do contribute to diabetes. These chemicals can disrupt fat metabolism, leading to lowered HDL (“good cholesterol”) levels. “Fatty acid metabolism, insulin resistance, and glucose metabolism are closely linked,” the report says. The NAS report found a variety of changes at the cellular level that could contribute to diabetes. However, it concluded that “family history, inactivity, and obesity” appear to be more important factors.

The most compelling studies find that pollution causes elevated levels of tumor necrosis factor (TNF). TNF is a powerful inflammatory chemical. Its function is to kill cancerous cells and other cellular bad guys. You don’t want it around healthy cells. If released into beta cells, it can lead to Type 1. It also increases insulin resistance, causing Type 2. So this could be a major way pollution of various kinds causes diabetes.

The last time I reported on this, I thought that stress was probably the biggest factor in causing diabetes. Pollution causes stress, which causes inflammation, which leads to insulin resistance. But it looks like pollution can cause inflammation directly, which makes sense when you think about your body trying to cope with dirty air and water. These “inflammatory cytokines,” like TNF, are part of our bodies’ response to polluted environments, just as they are to any other threat, like an infection. Building insulin resistance is part of what these cytokines do. Killing beta cells may be a side effect.

What can we do about it?
I’d like to ask readers what we can do about this pollution–diabetes connection. I guess we can move to less polluted environments. We can stop using so many chemicals in our households and eat more organic foods. But air pollution seems the biggest culprit. What can we do about that, or about any of it? How can we create a cleaner environment? Please let us know what you think.

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