PCBs plus obesity equals diabetes

It appears that fat alone is not the cause of an increased risk of type 2 diabetes. Duk-Hee Lee at Kyungpook National University in South Korea, and colleagues reported last year that people with higher levels of 6 different persistent organic pollutants (POPs) were more likely to have diabetes that people with low levels of POPs.

Now, a follow-up study, published in March 2007, suggests an association in non-diabetic people between certain pesticides, PCBs and insulin resistance – the diabetes precursor. In this study, fat people with POPs in their blood were more likely to develop insulin resistance than thin people with POPs, but the expected association between obesity and insulin resistance disappeared in people with no POPs. According to Lee, this suggests that it is possible that it is the POPs stored in fat tissue and not obesity itself, that is a key factor in the development of type 2 diabetes. The association exists at everyday background levels of POPs.

However, Matthew Longnecker from the National Institute of Environmental Health Sciences, North Carolina, suggests that people with diabetes, or a pre-diabetic condition, may clear POPs from their system at a slower rate, which would lead to increased POP concentrations over time. Long-term studies are planned.