A diet rich in fruits, vegetables, and whole grains is widely considered to be one of the best ways to support overall health and reduce the risk of many diseases, including cancer.
But new research from the University of Southern California Norris Comprehensive Cancer Center, part of the Keck School of Medicine at the University of Southern California, suggests an unexpected possibility. Research presented at the American Association for Cancer Research’s annual meeting shows that young Americans under age 50 who have never smoked and who consume more of these healthy foods than average may be at higher risk of developing lung cancer.
“Our study shows that young nonsmokers who consume more healthy foods than the general population are more likely to develop lung cancer,” said Jorge Nieva, MD, a medical oncologist and lung cancer expert at USC Norris and the study’s principal investigator. “These counterintuitive findings raise important questions about unknown environmental risk factors for lung cancer associated with beneficial foods that need to be addressed.”
Researchers suspect exposure to pesticides may play a role
Researchers stress that the food itself is not thought to be at fault. Rather, they suspect that exposure to pesticides may help explain this surprising pattern.
According to Nieva, commercially grown (non-organic) fruits, vegetables and whole grains generally contain higher levels of pesticide residues than dairy products, meat and many processed foods. He also pointed to previous research showing that agricultural workers exposed to pesticides over long periods of time have higher rates of lung cancer, supporting the hypothesis.
The study also found that women under 50 who had never smoked were more likely to develop lung cancer than men in the same age group. Women in the study also tended to eat more fruits, vegetables, and whole grains than men.
Increase in lung cancer cases among young non-smokers
Lung cancer has traditionally been thought to be associated with older people, smokers, and men. The average age at diagnosis was 71 years.
Smoking rates have steadily declined since the mid-1980s, contributing to a decline in lung cancer cases across the United States, but one group has not followed the trend. Lung cancer is more common among nonsmokers under the age of 50, especially women, who are more likely to develop lung cancer than men in the same age group.
To better understand why, researchers launched the Juvenile Lung Cancer Epidemiology Project. The study involved 187 people diagnosed with lung cancer before age 50. Participants provided information about diet, smoking history, demographics, and cancer diagnosis.
Most had never smoked and were diagnosed with a type of lung cancer that is biologically different from the type caused by regular smoking. A 2021 study by the Young Lung Cancer Epidemiology Project, the Young Lung Cancer Genomics Project, also found that lung cancer diagnosed before age 40 has a different subtype than lung cancer seen in older people.
Healthier diets were more common among patients
Researchers compared the participants’ diets to that of the general U.S. population using the Healthy Eating Index (HEI), a 1-100 scoring scale for overall diet quality.
The average HEI score for young non-smoking lung cancer patients was 65, compared to the national average of 57. Women in the study generally had higher scores than men.
Participants also reported eating more fruits, vegetables, and whole grains than the average American. On average, they ate 4.3 servings of dark green vegetables and legumes and 3.9 servings of whole grains each day. By comparison, the typical American adult consumes 3.6 servings of dark green vegetables and legumes and 2.6 servings of whole grains each day.
further research is needed
Nieva stressed that the link between pesticide exposure and lung cancer remains unproven, and further research is needed, especially in young people and women.
The researchers did not directly measure pesticide levels in the individual foods the participants ate. Instead, they used previously published data on average pesticide residues in food categories such as fruits, vegetables, and grains to estimate exposure.
The next stage of research will involve directly measuring pesticide levels in patients’ blood or urine samples. This study may help determine whether certain pesticides are more strongly associated with lung cancer risk than others.
“This study represents an important step toward identifying modifiable environmental factors that may contribute to lung cancer in young adults,” Nieva said. “Our hope is that these insights will inform both public health recommendations and future research on lung cancer prevention.”
The study was supported by Addario Lung Cancer Medical Institute, a nonprofit organization dedicated to advancing lung cancer research and treatment, along with AstraZeneca, the Beth Longwell Foundation, Genentech, GO2 for Lung Cancer, and Upstage Lung Cancer.
Additional funding was provided by the National Institutes of Health through grant number R25CA225513 and the National Cancer Institute through grant number P30CA014089.
