Young adults diagnosed with lung cancer despite never smoking reported eating healthier diets than the average American, according to preliminary research that has prompted scientists to investigate whether pesticide exposure could be one possible explanation.
The study examined 187 people who had been diagnosed with lung cancer by age 50. Most had never smoked and reported consuming relatively high amounts of fruits, vegetables, legumes and whole grains.
Their average Healthy Eating Index score was 65 out of 100, compared with a national average of 57. However, the research does not prove that healthy food causes lung cancer or that people who eat more produce have a greater overall risk of developing the disease.
What the Researchers Found
The research was conducted through the Epidemiology of Young Lung Cancer Project and presented at the 2026 annual meeting of the American Association for Cancer Research.
Participants provided information about their diet, smoking history, demographic characteristics and cancer diagnoses. Researchers then used the Healthy Eating Index to compare the quality of their diets with broader US dietary data.
According to the University of Southern California’s summary of the research, the patients consumed more fruits, vegetables and whole grains than the average American.
Participants reported an average of 4.3 daily servings of dark-green vegetables and legumes, compared with a national average of 3.6 servings. Their reported whole-grain consumption averaged 3.9 servings per day, compared with 2.6 servings among the general population.
Women in the study generally had higher Healthy Eating Index scores than men. Researchers said this observation was notable because lung cancer among younger nonsmokers appears to disproportionately affect women.
The Study Did Not Measure Lung-Cancer Rates
Headlines describing the participants as having “higher lung-cancer rates” because they ate healthier diets can be misleading.
The study primarily examined the diets of people who had already developed lung cancer. It did not follow a large group of healthy people over time to compare cancer incidence among those eating different diets.
Without an appropriate cancer-free control group, researchers cannot determine from this study alone whether eating more fruit, vegetables or whole grains increases a person’s chance of developing lung cancer.
Independent experts responding through the Science Media Centre said the conference abstract provided limited evidence of an association and did not establish a causal connection between diet, pesticides and lung cancer.
The findings should therefore be viewed as an unusual pattern that requires further investigation, not as proof that healthier diets are dangerous.
Why Researchers Are Asking About Pesticides
Fruits, vegetables and grains can contain small amounts of pesticide residue, particularly when they are grown using conventional agricultural methods.
Because participants reported eating relatively large quantities of these foods, the researchers considered whether repeated exposure to pesticide or herbicide residues might help explain the unexpected dietary pattern.
Previous research has associated high occupational pesticide exposure with lung-cancer risk among some agricultural workers. However, exposure experienced by farmworkers who mix, spray or regularly handle agricultural chemicals may be very different from the much smaller amounts consumers encounter through food.
The USC team did not directly test the participants’ food, blood or urine for pesticides. Instead, researchers used published average residue data for broad food categories to estimate possible exposure.
That method cannot determine which chemicals an individual encountered, how much entered the body or whether any particular pesticide contributed to the cancer.
Pesticide Exposure Remains a Hypothesis
Lead investigator Dr. Jorge Nieva, a medical oncologist and lung-cancer specialist at USC Norris Comprehensive Cancer Center, said the findings raise questions about an unidentified environmental factor associated with otherwise beneficial foods.
Pesticides are one proposed explanation, but other factors could produce the same pattern.
People who report eating healthy diets may differ from national averages in income, education, location, healthcare access or environmental exposure. They may live in areas with different levels of air pollution, radon, industrial chemicals or occupational hazards.
Dietary information can also be affected by recall errors. Participants may not remember their long-term eating patterns accurately, and a diet reported after diagnosis may not fully represent what they ate during the years when their cancer developed.
Researchers will need larger studies with suitable control groups and direct biological testing before determining whether pesticide exposure has any meaningful role.
These Findings Do Not Mean Fruits and Vegetables Cause Cancer
Fruits, vegetables, legumes and whole grains remain central components of widely accepted healthy eating recommendations.
They provide fibre, vitamins, minerals and other compounds associated with lower risks of cardiovascular disease, type 2 diabetes and several forms of cancer.
The new research does not justify reducing produce consumption or replacing nutritious foods with highly processed alternatives. Health experts commenting on the study have continued to recommend eating a varied diet rich in plant foods while the possible environmental connection is investigated.
The distinction between correlation and causation is essential. The patients happened to report healthier-than-average diets, but this does not establish that their diets produced their disease.
It is also possible that the observed difference resulted from limitations in how the study population was selected or compared with national dietary data.
Lung Cancer Can Affect People Who Never Smoked
Smoking remains the leading preventable cause of lung cancer, but it is not the only cause.
People who have never smoked can develop the disease after exposure to radon, secondhand smoke, air pollution, asbestos, diesel exhaust or other environmental and occupational hazards. Genetic and biological factors may also influence susceptibility.
The younger patients included in the USC study often had forms of lung cancer that were biologically different from cancers commonly associated with long-term tobacco use.
Many younger nonsmokers develop adenocarcinomas containing genetic alterations that can sometimes be treated with targeted therapies. Their disease may therefore have different causes and characteristics from traditional smoking-related lung cancer.
The American Cancer Society’s information on lung-cancer risk factors explains that radon is the leading cause of lung cancer among people who do not smoke.
This means pesticide exposure, even if future studies support a connection, would probably represent only one possible factor within a much broader and more complicated risk picture.
Why Young Women Are Receiving Particular Attention
Researchers have observed that lung cancer among younger nonsmokers appears especially important in women.
In the USC study, women reported healthier diets than male participants. The investigators suggested that this could potentially correspond with greater exposure to residues on fruits, vegetables and grains, although that relationship remains unproven.
Hormonal and genetic differences may also influence the development of certain lung cancers. Some tumors occurring in younger nonsmokers contain biological pathways that differ from those commonly found in smoking-related cancers.
Researchers need to separate these possible explanations before determining whether food-related environmental exposure contributes to the gender difference.
A dietary pattern alone cannot establish whether pesticides, hormones, air pollution, genetics or another factor caused an individual cancer.
Washing Produce Can Reduce Some Residues
Consumers concerned about pesticide exposure can wash fruits and vegetables under clean running water before eating or preparing them.
Rubbing firm produce and removing damaged outer leaves may reduce dirt, bacteria and some surface residue. Washing with soap, bleach or household cleaning products is not recommended because those substances are not intended for consumption.
Peeling certain foods can further reduce surface exposure, although it may also remove fibre and beneficial nutrients.
Cooking can reduce residues from some chemicals but may have little effect on others. The outcome depends on the pesticide, food and cooking method.
Choosing organic products may lower exposure to certain synthetic pesticides, but organic food is not entirely pesticide-free. Cost and availability may also make an all-organic diet unrealistic for many households.
Consumers should not stop eating conventional produce when organic options are unavailable. The established benefits of consuming fruits and vegetables remain stronger than the evidence supporting this preliminary pesticide hypothesis.
The Next Research Step Is Direct Testing
The USC researchers plan to investigate the theory by measuring pesticide levels or related chemical markers in patients’ blood and urine.
Direct testing could provide more reliable information than assigning estimated exposure based on food categories. It might also help researchers identify whether particular pesticides appear more frequently in younger lung-cancer patients than in comparable people without cancer.
Future studies will need to recruit larger groups, include cancer-free controls and account for environmental factors such as radon, air pollution, occupation and residential history.
Researchers may also need to examine patients’ diets over many years because lung cancer generally develops after prolonged biological changes rather than a brief exposure.
Until those studies are completed and peer reviewed, the pesticide explanation remains an early scientific question rather than a confirmed public-health conclusion.
What People Should Take From the Study
The study identified an unexpected characteristic among 187 younger lung-cancer patients: their reported diets were healthier than national averages.
It did not demonstrate that healthy diets increased cancer rates, and it did not directly show that pesticide residues caused any of the participants’ illnesses.
The responsible interpretation is that scientists have found a pattern worth investigating. It may eventually reveal an environmental risk factor, or further research may show that the apparent association resulted from study design, unmeasured differences or chance.
People should continue eating fruits, vegetables and whole grains while following normal food-safety practices. Those concerned about lung-cancer risk should focus on established precautions, including avoiding tobacco smoke, testing homes for radon and limiting unnecessary exposure to hazardous workplace chemicals and polluted air.
