Eating more fruits and vegetables tied to unexpected lung cancer risk

But new findings from USC Norris Comprehensive Cancer Center, part of Keck Medicine of USC, suggest there may be an unexpected risk for a specific group. Research presented at the annual meeting of the American Association for Cancer Research indicates that non-smoking Americans under age 50 who follow healthier diets could face a higher risk of developing lung cancer.

"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."

Possible Role of Pesticides in Lung Cancer Risk

Researchers believe the explanation may lie in environmental exposure, particularly pesticides used in agriculture. 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 pointed out that agricultural workers who are regularly exposed to pesticides tend to have higher rates of lung cancer, which supports the possibility of a connection.

The study also found that young women who do not smoke are diagnosed with lung cancer more often than men in the same age group. Women in the study also tended to consume more fruits, vegetables and whole grains than men.

Rising Lung Cancer Cases in Younger Non-Smokers

Lung cancer has traditionally been associated with older adults (the average age of lung cancer 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.

To better understand this trend, scientists launched the Epidemiology of Young Lung Cancer Project. The study included 187 patients diagnosed with lung cancer before age 50. Participants shared information about their demographics, diet, smoking history and diagnosis.

Most of these patients had never smoked. They were also diagnosed with a form of lung cancer that is biologically different from the type linked to smoking. A 2021 study from the Epidemiology of Young Lung Cancer Project, the Genomics of Young Lung Cancer 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 1-100.

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 vegetable 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.

More Research Needed on Pesticides and Cancer

Nieva emphasized that more research is needed to confirm any link between pesticide exposure and lung cancer in younger people, especially women.

In this 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 such as fruits, vegetables and grains.

The next step, according to Nieva, is to measure pesticide levels directly in patients through blood or urine samples. This could help determine whether certain pesticides are more strongly associated with lung cancer risk than others.

"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, a nonprofit focused on advancing lung cancer research and care, as well as AstraZeneca, the Beth Longwell Foundation, Genentech, GO2 for Lung Cancer and Upstage Lung Cancer.

Researchers also received funding from the National Institutes of Health, grant number R25CA225513 and the National Cancer Institute, grant number P30CA014089.

Disclosure: Dr. Nieva has received consulting payments from AstraZeneca and Genentech.