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Are there Environmental Causes for Type 1?

Sarah Howard is the national coordinator for the Diabetes-Obesity Working Group of the Collaborative on Health and the Environment. A mom with Type 1 with a child with Type 1, she has dedicated herself to scouring research to study possible environmental factors in rising rates of Type 1 diabetes. With a master’s degree in environmental policy and education from the the University of Michigan’s School of Natural Resources and Environment, she has had eight articles and letters published in peer-reviewed science journals.

Sarah shared some of her findings with Insulin Nation.

Is Type 1 diabetes all in the genes?

No, but genetics do play a role. The incidence of Type 1 diabetes has been increasing in children living in industrialized countries worldwide since the 1950s, on the order of 3% per year. That sort of increase cannot be explained by genetics alone. Certain genes, generally those linked to the immune system, are linked to Type 1 risk, and they can provide a protective effect or increase the risk. Anyone can develop this disease, even with low-risk genes—and not everyone with high-risk genes will develop the disease.

What is the role of the environment?

Type 1 researchers generally agree that the increasing incidence in Type 1 diabetes must be due to environmental factors. What those factors are, however, remains an area of active debate and research. Some of the top contenders include: viruses (either too many or too few), vitamin D deficiency, the gut microbiota, diet/nutrition (including cow’s milk or gluten), being overweight or obese, and environmental chemicals. It very well could be a combination of factors to blame, with different factors playing different roles in each person, depending on genetic make-up, and thus making it difficult to identify any root causes of the problem.

Researchers have been looking into viruses as a cause of Type 1 diabetes for over a hundred years, but conclusive proof remains elusive. A doctor first proposed that mumps could cause diabetes in 1864, and subsequent doctors also noticed that Type 1 diabetes peaks coincided with mumps outbreaks. There is good scientific evidence now that viruses could contribute to Type 1 diabetes development in humans (e.g., viruses can cause diabetes in lab animals; signs of viruses are present in the pancreases of people with diabetes), but some scientists still question the link. Even if certain viruses do cause diabetes in some people, the infection rates of many of these viruses have not changed much since the 1950s, and may not explain the increasing incidence of Type 1.

There is less research on environmental chemicals, but the few studies that do exist show associations between Type 1 in humans and exposure to air pollution, PCBs, and nitrate/nitrite. Some animal studies also show links with BPA, a widespread chemical used in plastics.

Despite the evidence possibly linking these and other factors to Type 1 development, there are no studies that show an effective means of preventing the condition. Few prevention trials have been done, and those that have been tried were unsuccessful.

Could environmental exposures during early life affect the chances you can develop Type 1 diabetes later in life?

Some studies say that a mother’s Vitamin D deficiency during pregnancy may increase her child’s later risk of Type 1, as could Vitamin D deficiency during infancy or childhood, while other studies find no such link. Likewise, scientists are conflicted about whether breastfeeding can sometimes be protective against Type 1. A number of researchers do, however, agree that introducing solid food to babies too early in life (before 3 months of age) is associated with an increased risk of autoimmunity or Type 1 development.

How can we learn more about the evolving body of research on this subject?

I keep track of the scientific research on this topic on my website, www.diabetesandenvironment.org. It is a lot of information on a lot of research, but worthwhile to read. Sources for the above article can be found there. Also, this fall the Collaborative on Health and the Environment (CHE) will be hosting a call, “Type 1 Diabetes and the Environment,” that will feature scientists focusing on this research. Visit CHE for more information and the date at www.healthandenvironment.org. The conversation will be archived on the site, as well.

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Sarah Howard and her son both have Type 1 diabetes. She works with the Collaborative on Health and Environment on their diabetes and obesity working group.

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