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, asks Newsweek.
A University of Southern California (USC) study recently 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 they 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,” said Jorge Nieva, MD, a medical oncologist, lung cancer specialist with USC Norris and lead investigator of the study.
“These counter-intuitive findings raise important questions about an unknown environmental risk factor for lung cancer related to otherwise beneficial food, which needs to be addressed.”
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 US 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 2.5m people were diagnosed and more than 1.8m 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% of all cases.
To investigate, researchers launched the Epidemiology of Young Lung Cancer Project, studying 187 people diagnosed with lung cancer by 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 Centre 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 realise it is not likely to be 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 UK-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 like avoiding smoking, maintaining a healthy weight, staying physically active, limiting alcohol intake, and participating in recommended screening programmes, 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 randomised controlled studies are carried out to understand why cancer patterns are shifting and how we can prevent more cases in the future.”
Study details
Dietary patterns in young lung cancer: mutation-specific environmental associations
Sarah Gorbatov, Marisa Bittoni, Anna Wu et al.
Abstract
Following peak tobacco incidence in the mid-1980’s there has been a large reduction in lung cancer incidence among men that has not been seen among women. Lung cancer at a young age is now more common among women than men, reversing a decades long pattern. We sought to characterise environmental exposures among young lung cancer patients to understand potential drivers of this change in the epidemiologic profile of young lung cancer patients. We analysed 187 patients (157 females, 84%) from the Epidemiology of Young Lung Cancer (YLC) study (ClinicalTrials.gov identifier: NCT04640259) using mutation-based grouping by shared biological mechanisms: EGFR Pathway (EGFR+ERBB2), Fusion Positive (ALK+ROS1+RET+NTRK), and Other/Mixed Mutations (including MET exon 14 skipping, TP53, KRAS, BRAF, and additional alterations). Of these, 166 patients (138 females, 83.1%) completed validated food frequency questionnaires. Dietary quality was assessed using the Healthy Eating Index-2015 (HEI-2015) and compared to U.S. reference values from NHANES. Dietary categories with elevated contaminant residue potential were identified using published literature. Statistical comparisons employed one-sample t-tests against reference means and chi-square tests for categorical variables. The EGFR groups and ALK groups had tobacco use history in 32.8% and 13.4% of patients respectively. All groups had similarly high levels of oral contraceptive exposure among women (75-100%). Dietary analysis revealed that EGFR Pathway, Fusion Positive, and Other/Mixed Mutations patients demonstrated HEI-2015 scores (out of 100) of 64.9 ± 10.7, 65.5 ± 9.8, and 63.5 ± 9.5 respectively, compared with the US reference of 58. YLC women demonstrated higher dietary quality scores than men (65.6 ± 9.7 vs. 61.8 ± 11.3), both exceeded U.S. reference values of 60 for females and 56 for males. These YLC patients also consumed more foods from dietary categories associated with elevated contaminant exposure potential, as reflected by higher HEI-2015 component scores (out of 5) for total vegetables (4.2 vs. 3.5), fruits (3.3 vs. 2.5), and whole grains (3.9 vs. 2.6). YLC patients have a diet pattern of higher diet quality, with higher exposure to whole fruits, vegetables and whole grains. While these food groups are presumed to have good health benefits, there is an emerging, under-appreciated literature that produce based whole foods often contain high pesticide/herbicide contaminants. Further investigation of the role of pesticide contaminated fruits/vegetables/whole grains is timely to assess its role, if any, in the changing lung cancer prevalence over the last 4 decades.
more likely than their male peers
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