Pregnant people who more closely followed the U.S. Dietary Guidelines had measurably lower levels of certain harmful chemicals in their urine compared to those with poorer dietary quality, but the same dietary choices had little protective effect against another set of chemicals that enter the body through routes other than food, according to a new study published July 9, 2026 in the American Journal of Clinical Nutrition.
The study, led by epidemiologists Diana Pacyga and Jessie Buckley at the UNC Gillings School of Global Public Health and funded through the NIH's ECHO Cohort, analyzed data from nearly 1,500 pregnant participants. The findings add meaningful but bounded evidence to one of maternal health's most persistent questions: can what you eat during pregnancy protect you from the chemicals all around you?
The honest answer, researchers say, is partly.
Why This Matters
Pregnant people cannot avoid chemical exposures entirely. Phthalates — a broad class of plasticizing chemicals — are found in food packaging, plastic containers, vinyl flooring, personal care products, and countless other consumer goods. Polycyclic aromatic hydrocarbons (PAHs) form when meat and other foods are grilled, smoked, or charred, and are also present in vehicle exhaust and cigarette smoke. Pesticide residues enter the food supply through conventional produce. These and dozens of other chemical classes are routinely detected in urine samples from pregnant people across all income levels and geographies.
Why does it matter during pregnancy specifically? Many of these chemicals are endocrine disruptors — substances that interfere with the body's hormonal signaling. Prenatal exposure during the period when fetal organs and systems are developing has been associated in prior research with preterm birth, reduced birth weight, neurodevelopmental differences, and changes in reproductive health. The evidence of harm is not uniformly conclusive across all chemical classes, but the precautionary principle supports minimizing exposures where practical.
The new study asks specifically whether following established U.S. dietary guidance — advice that already exists for nutritional reasons — can also serve as a secondary benefit for reducing chemical exposures.
What We Know So Far
The study, titled "Dietary guidelines adherence and pregnancy exposure to 10 classes of priority chemicals: An observational study in the ECHO Cohort," measured adherence to U.S. Dietary Guidelines among nearly 1,500 pregnant participants, then compared their urinary levels of more than 50 chemicals across 10 classes.
Researchers found that participants with higher dietary quality scores had lower levels of several chemical classes known to enter the body primarily through food. Notably, levels of one phthalate that leaches into food from plastic packaging were approximately 13% lower among participants with higher-quality diets. Levels of PAHs — the byproducts of high-heat cooking methods like grilling — were also lower in those with better dietary adherence, consistent with eating leaner proteins and fewer processed or charred foods.
"What we discovered is that following the U.S. Dietary Guidelines may have two benefits — helping pregnant people meet nutritional goals while also reducing exposures to some environmental chemicals," said Dr. Diana Pacyga of UNC Gillings, the study's lead author.
However, the same dietary choices had little measurable effect on exposure to certain replacement plasticizers — chemical compounds being used increasingly in products as older phthalates are phased out — and other chemical classes that enter the body through air, water, household dust, and personal care products rather than food.
Where the Concern Is Greatest
Chemical exposures during pregnancy are not uniform across populations. Several structural factors elevate risk for specific communities:
Urban environments. Cities with heavy traffic, industrial facilities, and older housing stock have higher background levels of PAHs, heavy metals, and particulate matter that contribute to chemical body burden through inhalation — routes dietary change cannot address.
Low-income communities. Access to fresh, minimally processed foods is inconsistent across income levels. Food deserts — areas with limited access to grocery stores selling whole foods — are disproportionately concentrated in lower-income urban and rural communities where Dietary Guidelines adherence is harder to achieve and chemical exposure from low-quality processed food packaging may be higher.
Workers with occupational chemical exposure. Pregnancy does not suspend occupational chemical exposure for essential workers in manufacturing, agriculture, cleaning, or healthcare settings.
None of these structural factors can be resolved by individual dietary choices. The researchers explicitly noted that their findings underscore why policy-level reduction of chemicals in consumer products and food packaging remains essential alongside individual-level guidance.
What Researchers Say
"Following the U.S. Dietary Guidelines may have two benefits — helping pregnant people meet nutritional goals while also reducing exposures to some environmental chemicals," Dr. Pacyga said, according to UNC Gillings' news release. She added that the effect is meaningful but incomplete: diet is one tool among several, not a comprehensive solution.
Dr. Jessie Buckley, Pacyga's research partner and an environmental epidemiologist at UNC Gillings, has in prior work emphasized that both individual-level and system-level interventions are needed to meaningfully reduce prenatal chemical exposures. A finding that diet helps with some exposures does not reduce the urgency of regulatory action on chemicals in packaging, personal care products, and environmental sources.
Independent environmental health researchers have noted that the ECHO Cohort design — which pools data across multiple study sites and includes diverse populations — provides a stronger evidence base for this type of finding than smaller single-site studies.
What the Evidence Shows — and What It Does Not
This is an observational study, meaning it cannot prove that dietary guideline adherence caused lower chemical exposures. It found associations — participants with better diets had lower levels of certain chemicals. Many factors influence both dietary quality and chemical exposures, and the study cannot fully separate dietary effects from other lifestyle and environmental factors.
The study used urinary biomarkers to measure chemical exposure at specific time points, which may not capture exposure fluctuations over the full course of pregnancy. The ~13% reduction in one phthalate class associated with higher dietary quality is statistically significant but modest — it does not represent near-zero exposure.
Current prenatal care guidelines have not been changed as a result of this study.
MedicalDaily Evidence Check
- Study type: Observational cohort study
- Published: July 9, 2026, American Journal of Clinical Nutrition
- Title: "Dietary guidelines adherence and pregnancy exposure to 10 classes of priority chemicals: An observational study in the ECHO Cohort"
- Institution: UNC Gillings School of Global Public Health; NIH ECHO Cohort
- Participants: ~1,500 pregnant people
- What it found: Higher dietary guideline adherence was associated with lower urinary levels of certain phthalates (~13% lower for one class) and PAHs
- What it did not find: A meaningful dietary effect on replacement plasticizers, certain persistent pollutants, and chemicals entering the body primarily through air, water, and non-food products
- Key limitation: Observational design cannot prove causation; dietary quality and chemical exposure both influenced by many factors
- What readers should know: Following dietary guidelines during pregnancy is beneficial nutritionally and may modestly reduce some food-sourced chemical exposures; it does not replace policy-level protections
Who Is Most Affected?
All pregnant people are exposed to some level of environmental chemicals — the variation is in degree. Groups with the highest exposures include:
- Pregnant people who regularly eat grilled, charred, smoked, or heavily processed foods (higher PAH exposure)
- Those who use plastic containers with hot food or liquids frequently (higher phthalate exposure from packaging)
- People living near high-traffic areas or industrial facilities (higher air-exposure chemical burden, not addressable by diet)
- Pregnant workers in manufacturing, agriculture, cleaning, or chemical environments (occupational exposure, not addressable by diet)
- Those who use certain personal care products with fragrance or phthalate-containing ingredients (exposure through skin and inhalation, not food-related)
Symptoms and Warning Signs
Environmental chemical exposures during pregnancy typically do not cause symptoms in the pregnant person that would prompt medical attention. The concern is not acute toxicity but long-term, low-level exposure during critical fetal developmental windows. This makes prenatal chemical exposure primarily a preventive concern rather than a diagnostic one.
If a pregnant person has occupational chemical exposure or known high environmental exposure, discussing it with an OB-GYN or maternal-fetal medicine specialist is appropriate. Some prenatal care practices can assess exposure risk and offer guidance specific to the patient's environment.
What You Can Do Now
- Follow U.S. Dietary Guidelines during pregnancy. Emphasis on lean proteins (especially fish, legumes, and poultry rather than red or processed meats), whole grains, fruits, and vegetables — and reduction of ultra-processed foods — aligns with both nutritional recommendations and this study's findings on chemical reduction.
- Reduce grilling and high-heat charring of food. PAHs form most abundantly when meat is charred, smoked, or cooked over an open flame. Choosing baked, steamed, or braised cooking methods reduces PAH formation.
- Minimize food contact with plastic , especially when food is hot. Use glass, stainless steel, or ceramic containers for storing and reheating food rather than plastic — particularly containers labeled with recycling codes 3, 6, or 7, which may contain phthalates or BPA.
- Do not microwave food in plastic containers. Heat significantly increases phthalate leaching from plastic into food.
- Eat fresh, whole foods over packaged goods where practical and accessible. More food packaging contact means more opportunity for chemical transfer.
- Talk to your OB-GYN about your specific environment. If you live near industrial areas, have occupational chemical exposure, or have concerns about specific exposures, your prenatal care provider can help assess your individual risk and connect you with resources.
- Understand that diet is one tool, not a complete solution. The same precautionary reduction steps apply regardless of how closely you follow dietary guidelines, because many exposure routes are outside of dietary control.
Cost and Access: What Patients Should Know
Following dietary guidelines during pregnancy is not inherently expensive, but access to fresh whole foods varies significantly by geography and income. For low-income pregnant people:
- WIC (Women, Infants, and Children) provides vouchers specifically for nutritious foods — including fresh fruits, vegetables, whole grains, and lean proteins — to eligible pregnant and postpartum people. Find your local WIC office at www.fns.usda.gov/wic .
- SNAP (Supplemental Nutrition Assistance Program) helps cover grocery costs for income-eligible families. Apply at benefits.gov .
- Community supported agriculture (CSA) programs and farmers markets in many cities accept WIC and SNAP benefits and provide access to fresh produce.
Environmental health resources for pregnant people vary by state. Organizations such as the Collaborative on Health and the Environment maintain current research summaries on prenatal chemical exposures and policy recommendations.
What Happens Next
The study's researchers noted that future work should examine whether specific dietary patterns — not just overall adherence to U.S. guidelines — may be more effective at reducing particular chemical classes. It also opens the door to studying whether policy interventions that reduce chemicals in packaging independently improve prenatal chemical profiles.
The ECHO Cohort, which pools data from more than 50 child cohort studies across the U.S. and is funded by the NIH, will continue to provide data for follow-up analyses. Whether any of this translates into updated prenatal dietary guidance will depend on how consistently these associations replicate across additional cohorts and chemical classes.
The Bottom Line
Pregnant people who followed U.S. Dietary Guidelines more closely had modestly lower levels of certain phthalates and PAHs in their urine, according to a new study of nearly 1,500 participants. The reduction is real but partial — diet cannot protect against the chemicals entering the body through air, water, household products, and personal care items. The most practical takeaway: following dietary guidelines during pregnancy is worth doing for multiple overlapping reasons, including modest chemical exposure reduction, and cooking methods like avoiding charring or grilling meat add incremental benefit. Broader chemical exposure during pregnancy remains a public health issue that requires regulatory solutions beyond what any individual can control through food choices alone.
