Eating a diet high in fruits and vegetables was found to have a surprising link to lung cancer among younger non-smokers, early research suggests.

The observational study, led by Jorge Nieva, M.D., of the USC Norris Comprehensive Cancer Center at Keck Medicine, was presented this month at the American Association for Cancer Research (AACR) annual meeting in San Diego. It has not yet been peer-reviewed. 

Researchers looked at dietary, smoking and demographic data for 187 patients who were diagnosed with lung cancer at age 50 or younger. 

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They found that among non-smokers, there was a link between healthier-than-average diets – rich in fruits, vegetables and whole grains – and the chance of lung cancer development.

Young lung cancer patients ate more servings of dark green vegetables, legumes and whole grains compared to the average U.S. adult, the researchers found.

The researchers hypothesized that pesticides applied to conventionally grown produce could be a possible factor in the disease association.

“Commercially produced (non-organic) fruits, vegetables and whole grains are more likely to be associated with a higher residue of pesticides than dairy, meat and many processed foods,” according to Nieva. He also noted that agricultural workers exposed to pesticides tend to have higher rates of lung cancer.

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“There is a large subset of lung cancer patients whose disease is not caused by smoking,” Nieva told Fox News Digital.

The disease is becoming more common in non-smokers 50 and younger, especially women – despite the fact that smoking rates have been falling for decades, the researcher noted.

“These patients tend to have eaten much healthier diets before their diagnosis than the average American,” he went on. “We need to support research into understanding why Americans – and women in particular – who no longer smoke very much are still having lung cancer,” he said.

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The study did have some limitations, Nieva acknowledged, primarily that it relied on survey data and was limited by the participants’ memories of their food intake.  

“Also, the survey participants were self-selected, and this could have biased the findings,” he told Fox News Digital.

“There is a large subset of lung cancer patients whose disease is not caused by smoking.”

The researchers did not test specific foods for pesticides, relying instead on average pesticide levels for certain types of food. Looking ahead, they plan to test patients’ blood and urine samples to directly measure pesticide levels, Nieva said.

Although the study shows only an association and does not prove that pesticides caused lung cancer, Nieva recommends that people wash their produce before eating and choose organic foods whenever possible.

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“This work represents a critical step toward identifying modifiable environmental factors that may contribute to lung cancer in young adults,” said Nieva. “Our hope is that these insights can guide both public health recommendations and future investigation into lung cancer prevention.”  

Dr. Marc Siegel, Fox News senior medical analyst, said the study is “interesting,” but that it “raises far more questions than it answers.”

“It is a small study (around 150) and observational, so no proof,” the doctor, who was not involved in the research, told Fox News Digital.

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“It is possible that the increased lung cancer risk could be due to pesticide exposure in whole farmed foods, but it is by no means certain,” Siegel went on. “How much exposure is needed? How much of it gets into food and in which areas? This requires much further study.”

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Kayla Nichols, communications director for Pesticide Action & Agroecology Network, a distributed global network, said the organization agrees with the study’s conclusion that more research should be done on the rise in lung cancer, particularly in individuals eating diets higher in produce and fiber.

“There is a bounty of existing research that already links pesticide exposure to increased risk of multiple types of cancers,” Nichols, who was also not involved in the study, told Fox News Digital. She called for more research on chronic, low-level exposures to pesticides, as well as more effective policies to protect the public from pesticide residues on food.

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The study was supported by the National Institutes of Health and the National Cancer Institute, as well as industry partners including AstraZeneca and Genentech, among others.

Fox News Digital reached out to several pesticide companies and trade groups for comment.