Healthy dietary patterns, such as the alternate Healthy Eating Index (aHEI), alternate Mediterranean Diet (aMED), and Dietary Approaches to Stop Hypertension (DASH), are widely endorsed in current dietary guidelines for their association with lower risks of cardiometabolic diseases and pregnancy complications. However, these same diets may also expose pregnant women to harmful environmental contaminants like heavy metals, polychlorinated biphenyls (PCBs), and per- and poly-fluoroalkyl substances (PFAS).
The Study and Its Importance
The study aimed to determine the chemical content of widely recommended healthy dietary patterns to identify which diets increase the risk of exposure to potentially harmful chemicals. This information could improve current dietary recommendations to promote health while minimizing exposure to toxic substances.
About the Study
The cohort included 1,618 ethnically and racially diverse pregnant women with an average maternal age of 28. Participants completed a food frequency questionnaire (FFQ) to obtain aMED, aHEI, and DASH scores. Researchers studied 88 of 97 chemicals with detection rates above 1%. Multivariate linear regression models and robustness analyses were used to assess the associations and ensure the validity of the findings.
Study Findings
Higher aMED and aHEI scores were associated with increased concentrations of several harmful chemicals, including perfluorododecanoic acid (PFDoDA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), mercury, PFASs, cesium, molybdenum, and thallium. These diets also correlated with lower levels of copper, zinc, and total metals.
Greater adherence to DASH, aMED, and aHEI in early pregnancy and peri-conception was significantly related to elevated plasma concentrations of PCBs, particularly aMED and aHEI.
Chemical Exposure from Food Groups
Variations in plasma chemical concentrations were primarily attributed to the consumption of different food groups and nutrients. Fish and eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) were the highest loading factors for all chemicals. Fish, EPA + DHA, and vegetables were also high-loading factors for metal levels within the plasma. Additionally, organochlorine pesticide (OCP) concentrations were positively correlated with vegetable consumption and the ratio of monounsaturated fatty acids (MUFAs) to saturated fatty acids (SFAs).
Racial and Ethnic Disparities
The study found that Asian and Pacific Islanders were more affected by the associations of healthy dietary pattern scores with chemical exposure compared to other racial groups. Seafood and aquatic products significantly contributed to the associations of aHEI and aMED with PFASs and PCBs, as most EPA + DHA is obtained from seafood and fish consumption. Due to bioaccumulation, fish are also common sources of heavy metals like silver and mercury.
Regulatory Context and Health Implications
To date, specific PFAS control standards have not been established for human blood. However, the U.S. Environmental Protection Agency (EPA) has reduced environmental limits for PFAS exposure due to their potential metabolic and reproductive toxicity, even at lower doses.
Comparing to Existing Literature
Previous studies on similar associations between dietary patterns and chemical concentrations, including one using umbilical cord blood, have documented inconsistent findings. Many of these studies had small sample sizes and did not consider variations in food, diet, and nutrient intake. In contrast, this study assessed multiple dietary patterns and a wide range of chemicals, which can help identify toxic substances more comprehensively.
Conclusions
The findings demonstrate that chemical exposure was higher with greater adherence to healthy dietary patterns. Fish and its associated nutrients largely contributed to these associations, which were particularly strong among Asian and Pacific Islanders.
Study Strengths and Limitations
Notable strengths of the study include the assessment of three widely recommended dietary patterns combined with a broad array of environmental chemicals. The use of a well-validated FFQ allowed researchers to obtain comprehensive information on various covariates and long-term habitual dietary patterns.
The main limitation was the inability to control for unmeasured confounding factors, a common issue with observational studies. Additionally, the FFQ may not have captured commonly consumed foods in each ethnicity and race, underscoring the need for the development of ethnicity- or race-specific FFQs.
Implications for Future Research
These findings highlight the need for further research to develop dietary recommendations that consider both nutritional benefits and chemical exposure risks. Understanding the balance between promoting h
