Coordinator of the CHE Diabetes-Obesity Spectrum Working Group
What did Dr. Lind and her colleagues find? That three of the four phthalate metabolites they measured were associated with diabetes in elderly Swedish adults—even after adjusting for obesity, smoking, exercise, and other factors linked to diabetes. People with higher phthalate metabolite levels had about twice the risk of diabetes as those with lower levels. In this study, the phthalate metabolites linked to diabetes included MMP, MEP, and MiBP, all of which are metabolites of phthalates used in personal care products. Taking the research one step farther, the authors found that MMP and MEP were related to insulin resistance, while MiBP was related to poor insulin secretion. (The phthalate MEHP, a breakdown product of the common plasticizer DEHP, was not related to diabetes or the other health effects). These four phthalate metabolites were detected in almost all study participants.
A smaller, previous study of Mexican women also found an associated between phthalates and diabetes, although the specific phthalate metabolites linked to diabetes were different (all were DEHP metabolites) (Svensson et al. 2011.
No other human studies have investigated phthalates together with diabetes.
Two longitudinal studies, however, have found associations between phthalate metabolite levels and later body size measures, one study in children (Teitelbaum et al., 2012) and one study in the elderly (Lind et al., 2012 ). In a cross-sectional sample of the US population (NHANES), phthalate metabolites were associated with higher waist circumference and insulin resistance in adult men (Stahlhut et al., 2007). Animal studies also find that exposure to phthalates in utero can affect blood glucose levels and insulin secretion later in life (Lin et al., 2011 ).
Phthalates bind with the receptors of PPAR hormones, which are known to play a role in blood glucose levels, insulin resistance, and fat formation. In fact, pharmaceutical drugs that are PPAR antagonists are used to treat type 2 diabetes and can decrease insulin resistance (Lind et al., 2012). The association between phthalates and diabetes is not entirely surprising then.
Can phthalates contribute to the development of diabetes? We don’t know yet, but this study adds to the existing evidence that exposure to phthalates at levels seen in the general population may influence the major processes that lead to type 2 diabetes.