According to Gram Research analysis, people who eat healthier diets have higher levels of arsenic and mercury in their bodies, but lower levels of cadmium. A 2026 study of 4,944 Americans found that better diet quality was associated with increased urinary arsenic and blood mercury, likely because nutritious foods like vegetables and seafood can accumulate these metals from soil and water. However, this doesn’t mean you should avoid healthy foods—the nutritional benefits still outweigh the risks, and practical steps like washing produce can reduce exposure.
A major study of nearly 5,000 Americans found that eating a healthier diet comes with an unexpected trade-off: higher exposure to certain environmental chemicals like arsenic and mercury. Researchers analyzed what people ate and measured chemicals in their blood and urine, discovering that while nutritious foods like vegetables and seafood are good for you, they can also contain more pesticide residues and heavy metals from soil and water. The good news is that some chemicals like cadmium actually decreased with better eating habits. The study suggests we need smarter strategies to get nutrition benefits while reducing our exposure to harmful substances.
Key Statistics
A 2026 cross-sectional study of 4,944 Americans from NHANES 2017-2020 found that higher diet quality scores were positively associated with urinary arsenic (β = 0.002) and blood mercury (β = 0.005), but negatively associated with blood cadmium (β = -0.001).
According to research reviewed by Gram, vegetables and greens were the primary dietary contributors to higher nitrate exposure in a nationally representative U.S. sample of 4,944 people, while seafood and plant proteins were linked to elevated mercury and arsenic levels.
A validation analysis using 11,739 Americans across NHANES 2013-2020 confirmed that the associations between diet quality and chemical exposures were generally stable across multiple years, supporting the reliability of the findings.
Fruit consumption showed an inverse association with blood cadmium levels in the 2026 study, suggesting that certain components of healthy diets may offer protective effects against some environmental contaminants.
The Quick Take
- What they studied: Whether eating a healthier diet affects how many environmental chemicals (like pesticides, arsenic, and mercury) people have in their bodies
- Who participated: Nearly 5,000 Americans from a nationally representative survey (NHANES 2017-2020), plus a larger validation group of 11,739 people from 2013-2020 to confirm the findings
- Key finding: People who ate healthier diets had higher levels of arsenic and mercury in their bodies, but lower levels of cadmium. The connection was stronger for some chemicals than others, and the pattern wasn’t always straightforward.
- What it means for you: Eating nutritious foods is still important for your health, but you should be aware that some healthy foods may contain more chemical contaminants. This doesn’t mean you should stop eating vegetables or seafood—instead, it highlights the need for better food safety standards and washing practices.
The Research Details
Researchers used data from a large, ongoing U.S. health survey called NHANES that tracks what Americans eat and measures chemicals in their blood and urine. They scored each person’s diet using a system called the Healthy Eating Index 2020 (HEI-2020), which rates how well someone follows nutritional guidelines based on foods like vegetables, fruits, whole grains, and proteins.
They then looked for connections between diet quality scores and the levels of various environmental chemicals found in people’s bodies. The chemicals they measured included pesticide residues (like nitrates), heavy metals (arsenic, mercury, and cadmium), and industrial chemicals (like PFOA, a chemical used in non-stick cookware). They used statistical methods to account for differences between people, like age and income.
To make sure their findings were reliable, they tested the same patterns using data from a longer time period (2013-2020) with more than 11,000 people. This validation step helps confirm that the results weren’t just a one-time coincidence.
This research approach is important because it looks at real-world eating patterns and actual chemical exposures in people’s bodies, rather than just studying single foods in a lab. By using a nationally representative sample, the findings apply to the general American population. The validation with a larger dataset strengthens confidence that these patterns are real and consistent over time.
This study has several strengths: it uses a large, representative sample of Americans, measures actual chemicals in blood and urine (not just estimates), and validates findings across multiple years of data. However, because it’s observational (watching what people naturally eat rather than assigning them to diets), we can’t prove that healthier eating directly causes higher chemical exposure—other factors could be involved. The study also measures chemicals at one point in time, so we don’t know if these patterns persist long-term.
What the Results Show
People who scored higher on the healthy eating index had higher levels of three chemicals in their bodies: nitrates in urine, arsenic in urine, and mercury in blood. The increases were small but measurable. For example, for every 10-point increase in diet quality score, arsenic levels went up slightly. Interestingly, the relationship wasn’t always straightforward—for arsenic and mercury, the pattern was nonlinear, meaning the effect wasn’t consistent across all diet quality levels.
On the positive side, better diet quality was associated with lower levels of cadmium (a toxic heavy metal) and PFOA (an industrial chemical). This suggests that some aspects of healthier eating may actually protect against certain contaminants.
When researchers looked at specific foods, they found that vegetables and greens were the main contributors to higher nitrate levels, which makes sense since plants naturally contain nitrates. Seafood and plant-based proteins were linked to higher mercury and arsenic, likely because these foods can accumulate metals from water and soil. Fruits were associated with lower cadmium levels, suggesting some protective effect.
The study found that the associations between diet quality and chemical exposure were generally stable across different time periods (2017-2020 and 2013-2020), suggesting these patterns are consistent. The nonlinear relationships for arsenic and mercury suggest that the effect of diet quality on these metals may be stronger at certain diet quality levels than others. Component-level analysis revealed that not all healthy foods contribute equally to chemical exposure—some foods like vegetables drive nitrate exposure, while others like fruits may offer protection.
Previous research has shown that individual foods can contain environmental chemicals, but this is one of the first studies to comprehensively examine how overall diet quality relates to multiple chemical exposures simultaneously. Most prior work focused on single chemicals or single foods. This research aligns with growing evidence that ‘healthy’ foods can be contaminated with environmental pollutants, and adds nuance by showing that the relationship is complex—some chemicals increase with better diets while others decrease.
This study cannot prove that eating healthier causes higher chemical exposure because it only observes patterns, not cause-and-effect. People who eat healthier diets may differ in other ways (like where they live or their income) that also affect chemical exposure. The study measures chemicals at one point in time, so we don’t know if these levels stay consistent or change over months and years. Additionally, the study doesn’t account for food preparation methods (like washing produce) that could reduce chemical exposure. Finally, while the sample is nationally representative, it only includes U.S. data, so results may not apply to other countries with different food sources and regulations.
The Bottom Line
Continue eating a healthy diet rich in vegetables, fruits, and lean proteins—the nutritional benefits far outweigh the risks from chemical exposure at current levels. However, take practical steps to reduce chemical exposure: wash produce thoroughly, peel vegetables when possible, vary the types of seafood you eat (to avoid accumulating metals from a single source), and choose organic produce for items with high pesticide residues when budget allows. This research supports the need for stronger food safety regulations and better monitoring of environmental contaminants in food sources.
Everyone should care about this research, especially pregnant women, children, and people with chronic health conditions who may be more sensitive to environmental chemicals. If you eat a lot of seafood or rely heavily on vegetables as your protein source, this information is particularly relevant. Policymakers and food safety officials should use this research to improve standards for monitoring and reducing contaminants in food.
Changes in chemical exposure levels in your body would take weeks to months to appear after changing your diet, since these chemicals accumulate over time. You won’t see immediate health effects from the chemical exposures measured in this study, but reducing exposure over years may help prevent long-term health problems. Focus on the proven benefits of healthy eating (better heart health, lower disease risk) while taking practical steps to minimize chemical exposure.
Frequently Asked Questions
Does eating healthy vegetables increase arsenic and mercury in your body?
Healthier diets are associated with slightly higher arsenic and mercury levels, primarily from vegetables and seafood which can accumulate these metals from soil and water. However, the increases are small, and the nutritional benefits of eating these foods far outweigh the chemical exposure risks at current levels.
Should I stop eating seafood and vegetables because of this study?
No. This study shows associations, not proof that these foods cause harm. The nutritional benefits of vegetables and seafood are well-established and substantial. Instead, wash produce thoroughly, vary your seafood sources, and consider organic options for high-pesticide items to reduce exposure while maintaining a healthy diet.
What foods reduce chemical exposure according to this research?
Fruits showed an inverse association with cadmium, suggesting they may offer some protective effect. The study indicates that varying your diet across different food sources, rather than relying heavily on one type, helps minimize accumulation of specific contaminants in your body.
How long does it take to reduce chemical levels by eating better?
Chemical levels in your body change gradually over weeks to months as your diet changes, since these substances accumulate over time. Consistent dietary improvements and contamination-reduction practices (like washing produce) will have cumulative benefits, but don’t expect immediate changes.
Is this study proof that healthy eating is bad for you?
No. This is an observational study showing associations, not cause-and-effect. The study actually supports eating healthy while being mindful of food safety practices. The documented health benefits of nutritious diets significantly outweigh the measured chemical exposures in this research.
Want to Apply This Research?
- Log your daily diet quality by tracking servings of vegetables, fruits, whole grains, and lean proteins. Use the app to calculate a weekly Healthy Eating Index score and correlate it with any symptoms or health markers you’re monitoring (like energy levels or digestion). This helps you see patterns between your diet quality and how you feel.
- Set a goal to wash all produce under running water for 15-30 seconds before eating, and track this habit in the app. Add a weekly reminder to vary your protein sources (rotating between different types of seafood, plant proteins, and poultry) to avoid accumulating metals from a single source. Log which produce items you buy organic versus conventional to optimize your choices based on pesticide risk.
- Track your diet quality score weekly and note any changes in how you feel. If you’re concerned about chemical exposure, discuss periodic blood or urine testing with your doctor to monitor specific chemicals. Use the app to identify which foods contribute most to your diet quality score, then research and note the pesticide/contamination profiles of those specific foods to make informed choices.
This research shows associations between diet quality and chemical exposure but does not prove that healthy eating causes chemical accumulation or health problems. The chemical levels measured are within ranges found in the general population and do not necessarily indicate health risk. This article is for educational purposes and should not replace professional medical advice. If you have concerns about chemical exposure or your diet, consult with a healthcare provider or registered dietitian. Pregnant women, children, and people with specific health conditions should discuss dietary choices with their doctor.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.