Study Observes Link Between Healthier Diet Scores and Early-Onset Lung Cancer in Nonsmokers

A study presented at a scientific conference has observed an association between higher scores on a healthy diet index and early-onset lung cancer among people who have never smoked. The research, which has not yet been published in a peer-reviewed journal, involved 187 patients diagnosed with lung cancer before age 50.

Researchers hypothesize that pesticide residues on conventionally grown produce may be a factor, but emphasize the findings show correlation, not causation, and that more direct research is needed.

Study Design and Key Findings

The research analyzed data from the Epidemiology of Young Lung Cancer study, a nationwide observational project examining factors linked to cancer in younger adults.

Participants: The study group consisted of 187 patients diagnosed with lung cancer before age 50. Approximately 78% of participants were women, and the majority in each tumor pathway group had never smoked.

Diet Assessment: Researchers assessed dietary habits using food-frequency questionnaires and the Healthy Eating Index (HEI), where a higher score indicates closer adherence to U.S. dietary guidelines.

Dietary Comparisons: The study found that participants had an average HEI score of approximately 65, compared to the national average score of 57 for U.S. adults. Participants reported consuming more servings of dark green vegetables, legumes, and whole grains than the average adult.

Proposed Hypothesis and Research Context

The observed association between healthier diet scores and early-onset lung cancer in nonsmokers prompted researchers to propose a hypothesis for further investigation.

Pesticide Hypothesis: Researchers suggested that environmental exposures, particularly pesticide residues on commercially grown (non-organic) fruits, vegetables, and whole grains, could be a contributing factor. They noted that agricultural workers with regular pesticide exposure tend to have higher rates of lung cancer.

Important Context: The study did not directly measure pesticide levels in the foods consumed or in the participants' bodies. Instead, it estimated potential exposure using existing data on average pesticide residue levels in food categories.

Broader Cancer Trends: The research is situated within a context where overall lung cancer rates have declined alongside reduced smoking, but incidence has been increasing among younger nonsmokers, particularly women. The average age of lung cancer diagnosis in the U.S. is 70 years.

Study Limitations and Researcher Statements

The researchers and external commentators highlighted several important limitations of the study.

Lead researcher Dr. Jorge Nieva and others stressed that the finding demonstrates an association, not proof that eating fruits, vegetables, or whole grains causes cancer.

Study Design: The study was retrospective, meaning it looked at people who already had cancer rather than following healthy individuals over time. It also relied on self-reported dietary data and involved a relatively small sample size.

Contrast with Larger Body of Evidence: As noted in commentary on the research, large, long-term studies and meta-analyses involving hundreds of thousands of people have consistently found that higher fruit and vegetable intake is associated with a lower risk of lung cancer, particularly among smokers. These larger studies inform current public health dietary guidelines.

Next Steps and Recommendations

Researchers outlined plans for further investigation and provided cautious recommendations.

Future Research: Dr. Nieva stated that more work is needed to understand the potential link. Planned next steps include directly measuring pesticide metabolites in the blood or urine of lung cancer patients and examining different geographic regions and chemical uses.

Current Advice: While emphasizing the study does not prove causation, researchers noted that washing produce under running water and varying the types of fruits and vegetables consumed can help reduce potential exposure to surface residues. Choosing organic produce is an option for those concerned about pesticides.

Study Support and Disclosure: The research was supported by the National Institutes of Health, National Cancer Institute, and industry partners including AstraZeneca and Genentech. Dr. Nieva has received consulting payments from AstraZeneca and Genentech.