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It has long been believed that one of the best ways to ward off cancer is by following a healthy, balanced diet full of tasty fruits and vegetables. But what if what is inside those foods is actually contributing to the development of disease?
A new University of Southern California (USC) study has found that young, non-smoking lung cancer patients tend to eat healthier diets than the general population, a surprising pattern that has led researchers to ask whether pesticide residues on fruits, vegetables and whole grains—or anything else—could be playing a role.
The findings are preliminary, and the scientists behind them are urging caution while further research will be carried out.
What the Study Found
“Our research shows that younger non-smokers who eat a higher quantity of healthy foods than the general population are more likely to develop lung cancer,” Jorge Nieva, MD, a medical oncologist, lung cancer specialist with USC Norris and lead investigator of the study, said in a statement. “These counter-intuitive findings raise important questions about an unknown environmental risk factor for lung cancer related to otherwise beneficial food that needs to be addressed.”
Newsweek reached out to USC for more information.
Nieva said commercially grown, non-organic produce generally carries higher pesticide residue levels than dairy, meat and many processed foods. He also cited earlier research showing that farmworkers with long-term pesticide exposure have higher rates of lung cancer, which he said lends support to the theory.
Rethinking Who Gets Lung Cancer
Lung cancer has traditionally been linked to older adults, smokers, unhealthy eaters and men, with an average diagnosis age of 71. But while U.S. smoking rates have fallen steadily since the mid-1980s, driving down overall lung cancer cases, that trend has not held for one group; non-smokers aged 50 and younger, particularly women, who are now more likely than their male peers to develop the disease, despite being shown in research to eat healthier on average.
Lung cancer is the most common cancer worldwide and the leading cause of cancer death.
In 2022, about 2.5 million people were diagnosed and more than 1.8 million died. Tobacco still drives most cases globally, but as smoking rates decline, the share of lung cancers diagnosed in people who have never smoked is climbing—now between 10 and 20 percent of all cases.
To investigate, researchers launched the Epidemiology of Young Lung Cancer Project, studying 187 people diagnosed with lung cancer by age 50. Most had never smoked and had a form of the disease that differs biologically from typical tobacco-related lung cancer that is better known, echoing a 2021 companion study that found lung cancers in people under 40 form distinct subtypes.
Participants’ diets were scored using the Healthy Eating Index, which rates diet quality from 1 to 100. The patient group averaged 65, well above the national average of 57, with women scoring even higher than men. Patients also reported eating more dark green vegetables, legumes and whole grains than typical American adults.
Medical Experts Urge Caution
The research, supported by Addario Lung Cancer Medical Institute, AstraZeneca and Genentech among others, offers new routes for investigating the rise in lung cancer, but medical experts urge caution.
Dr. Kristin Higgins, chief clinical officer at City of Hope Cancer Center Atlanta, told Newsweek: “The findings from this study point to environmental factors playing a part—pesticides in fresh fruits and vegetables. It is important that people realize it is not likely the fruits or vegetables themselves causing heightened cancer risks, but the pesticides used to grow these products. We can’t conclude that consuming these products causes cancer, but the association does point to pesticides being problematic and something we should try to avoid.”
Dr. Semiya Aziz, a U.K.-based general practitioner and founder of Say GP, told Newsweek that cancer in younger adults is rarely traced to one cause.
“The evidence is not strong enough to support the conclusion that pesticides in conventionally grown fruit and vegetables are causing lung cancer in the young,” she said, pointing instead to a mix of possible factors including obesity, sedentary lifestyles, alcohol use, air pollution and genetics. “What is clear, however, is that the benefits of a diet rich in plant-based foods remains well established.”
Nieva stressed the pesticide theory remains unproven. The researchers did not measure pesticide levels in the food participants actually ate; instead, they estimated exposure using published data on average residues in food categories.
“As a doctor my message to the public would be one of informed awareness rather than a cause for alarm,” Aziz said. “We should continue to promote a healthy balanced diet, since current research validates the numerous health benefits. Other lifestyle measures such as avoiding smoking, maintaining a healthy weight, staying physically active, limiting alcohol intake, and participating in recommended screening programs, should continue to be reinforced, since these measures will not only pick up early stages of disease, but will instigate appropriate treatments.
“At the same time, it is essential that ongoing high‑quality research and randomized controlled studies are carried out to understand why cancer patterns are shifting and how we can prevent more cases in the future.”
Reference
University of Southern California – Health Sciences. “Why are healthy young non-smokers developing lung cancer?” ScienceDaily. July 2026. www.sciencedaily.com/releases/2026/07/260712011758.htm.
Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang
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