– Pesticide residue on conventionally grown produce is a suspected culprit, researchers say –
A surprising new study presented at the annual meeting of the American Association for Cancer Research suggests that young non-smokers who eat a very healthy diet—rich in fruits, vegetables, and whole grains—may face a higher risk of developing lung cancer, with researchers pointing to pesticide exposure as a possible hidden culprit.
The research, conducted at USC Norris Comprehensive Cancer Center, part of Keck Medicine of USC, found that patients under age 50 diagnosed with lung cancer had better-than-average diets. This counter-intuitive finding raises urgent questions about environmental risk factors in otherwise beneficial foods.
“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 and 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 that needs to be addressed.”
The Pesticide Hypothesis
Researchers believe the explanation may lie in pesticide residue. According to Nieva, commercially produced (non-organic) fruits, vegetables, and whole grains are more likely to carry higher levels of pesticide residue compared to dairy, meat, and many processed foods. He also noted that agricultural workers who are regularly exposed to pesticides tend to have higher rates of lung cancer, supporting a potential connection.
In the study, researchers did not directly measure pesticide levels in the foods participants ate. Instead, they estimated exposure using existing data on average pesticide levels in food categories. The next step, according to Nieva, is to measure pesticide levels directly in patients through blood or urine samples to determine whether certain pesticides are more strongly associated with lung cancer risk than others.
Rising Cases in Younger Non-Smokers
Lung cancer has traditionally been associated with older adults (average age of onset is 71), smokers, and historically, men. While smoking rates have declined since the mid-1980s—leading to an overall drop in lung cancer cases in the United States—one group stands out. Non-smokers age 50 and younger, particularly women, are now experiencing increasing rates of lung cancer and are more likely than men to develop the disease.
The study, part of the Epidemiology of Young Lung Cancer Project, included 187 patients diagnosed with lung cancer before age 50. Participants shared information about their demographics, diet, smoking history, and diagnosis. Most had never smoked and were diagnosed with a form of lung cancer biologically different from the type linked to smoking. A 2021 study from the same project showed that lung cancer subtypes in people under 40 differ from those seen in older adults.
Healthier Diet Scores Among Lung Cancer Patients
To evaluate diet quality, researchers used the Healthy Eating Index (HEI), which scores diets on a scale of 1 to 100. Young non-smoking lung cancer patients had an average HEI score of 65, compared to the national average of 57. Women in the study generally had higher HEI scores than men.
Participants also reported eating more fruits, vegetables, and whole grains than the average American. On average, they consumed 4.3 servings of dark green vegetables and legumes and 3.9 servings of whole grains daily. By comparison, the typical U.S. adult eats 3.6 servings of dark green vegetables and legumes and 2.6 servings of whole grains per day.
What This Means for Public Health
Nieva stressed that more research is needed to confirm any link between pesticide exposure and lung cancer in younger people, especially women. However, he noted that the findings represent a critical step toward identifying modifiable environmental factors that may contribute to lung cancer in young adults.
“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.”
The research is supported by the Addario Lung Cancer Medical Institute, AstraZeneca, the Beth Longwell Foundation, Genentech, GO2 for Lung Cancer, and Upstage Lung Cancer. Researchers also received funding from the National Institutes of Health and the National Cancer Institute. Nieva has received consulting payments from AstraZeneca and Genentech.