Organic pollutants found in Mediterranean diet up GDM risk

Adherence to a healthy dietary pattern, such as the Mediterranean diet (MedDiet), may reduce the risk of gestational diabetes mellitus (GDM) but appears to increase exposure to harmful chemicals, according to a Singapore study presented at ADA 2024.

“Healthy diet, such as greater adherence to MedDiet, has been associated with a lower risk of GDM,” said lead author Dr Guoqi Yu, Department of Obstetrics and Gynaecology, National University of Singapore, Singapore. “However, foods characterizing MedDiet, such as fish and vegetables, are high in certain persistent organic pollutants (POPs) that are known to increase GDM risk.”

Yu and his team conducted this study based on a prospective multi-racial pregnant cohort in the US, the NICHD Fetal Growth Study, which involved a total of 2,802 participants. A validated food frequency questionnaire was used to derive adherence to MedDiet in periconception/early pregnancy.

Blood samples were collected at 8‒13 gestational weeks and used to measure 76 POPs of different classes overall. Yu and colleagues categorized pregnant women into four mixed groups based on the median values of aMED and POP concentrations. Finally, they examined the combined associations of adherence to MedDiet and POPs with GDM risk using binary logistic regression models.

Healthy diet

Adherence to MedDiet and exposure to POPs were jointly associated with a higher risk of developing GDM. Such risk was lowest among women with higher adherence scores and low POP levels. [Diabetes 2024;73(Suppl 1):130-OR]

Specifically, GDM risk was approximately lower by 80 percent among women with a higher MedDiet adherence score and low levels of polychlorinated biphenyls (PCBs) than those with a lower adherence score and high PBC levels (odds ratio, 0.18, 95 percent confidence interval, 0.04‒0.86; p=0.041 for interaction).

“The lowest GDM risk was observed among individuals who consumed both a healthy diet and were exposed to low concentrations of POPs, especially PCBs,” Yu said.

Of note, higher concentrations of POPs tended to reduce the beneficial effects of adherence to a MedDiet on GDM risk reduction. For instance, women with a higher adherence score and high PCB levels showed no decrease in GDM risk as opposed to those with a higher adherence score and low PCB levels.

“This study is one of the first to examine the association of healthy diet in early pregnancy with GDM while considering POP levels, and results suggest that future endeavours for promoting a healthy diet for the prevention of GDM may consider optimizing environmental contaminants such as POPs simultaneously,” Yu said.

Fish consumption

A potential contributor to chemical exposure was the consumption of fish. Fish and omega-3 fatty acids “had the highest loading factors for total chemical variation, as well as PCBs, polyfluoroalkyl substances, and metal levels,” Yu said.

Furthermore, the associations between dietary patterns and these chemicals were “more pronounced among Asians and Pacific Islanders,” he added.

“A more balanced diet with healthy food and less toxic chemicals merits consideration,” Yu said, noting that future studies may consider the joint and individual associations between dietary patterns and environmental chemicals.