Fruit and veg have always been promoted as staples of a balanced diet, yet emerging research is prompting questions about whether they could be linked to an increase in certain cancers among health-conscious younger adults.
Healthcare professionals routinely recommend eating more produce to help protect against a range of illnesses, cancer included. However, a rise in lung cancer diagnoses among non-smokers under 50 has pushed researchers to search for possible environmental explanations.
A new study suggests one potential factor may be long-used agricultural pesticides. The researchers propose that lingering chemical residues on some crops could be contributing to the worrying pattern of younger people developing serious cancers.
Lead investigator in the study, Jorge Nieva, a lung cancer specialist at the University of Southern California (USC), said: “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.”
Nieva said the results highlight the need to pinpoint what’s driving the trend. He told the Mirror: “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.”
Although the findings may sound alarming for people trying to eat well, the study’s team emphasized that the suspected issue is not fruits and vegetables themselves, but the way some are produced—particularly when pesticides are used in growing and handling.
One practical approach, they noted, is choosing organic options where possible to reduce exposure from produce treated with pest-control chemicals. They also suggested that items such as meat, dairy, and many processed foods may be less directly affected by pesticide application on crops, though dietary choices remain personal and complex.
Backing the idea that pesticide exposure could matter, Dr Nieva pointed to evidence that farm workers who regularly handle these chemicals show higher rates of lung cancer.
To explore why lung cancer is increasing specifically in under-50s—the only age group seeing a rise—researchers launched the Epidemiology of Young Lung Cancer Project.
The project surveyed 187 people diagnosed with lung cancer before turning 50, collecting details about diet, personal history, and smoking status.
A significant portion reported never having smoked, yet they still developed lung cancer—often a form that differs from the cancers most commonly associated with tobacco. When researchers assessed diets using the Healthy Eating Index (HEI) on a 1–100 scale, a notable pattern emerged.
On average, those diagnosed with this non-smoker lung cancer had higher HEI scores than the general population, landing around 67/100 compared with a typical score of about 57.
Overall, participants reported eating more of several foods typically considered healthy, including dark leafy greens and legumes, and they also consumed more grains than the wider population.
Because the researchers did not directly test pesticide levels in each individual’s food, they instead estimated likely exposure by using published data showing how frequently different foods carry pesticide residues.
The team hopes the survey will help lay the groundwork for more detailed research, including measuring pesticide markers in blood and urine and identifying which specific chemicals, if any, may be associated with the pattern.
Dr Nieva said: “This work represents a critical step toward identifying modifiable environmental factors that may contribute to lung cancer in young adults. Our hope is that these insights can guide both public health recommendations and future investigation into lung cancer prevention.”
The findings are due to be presented at the annual meeting of the American Association for Cancer Research, but some cancer experts have urged caution in interpreting the results.
Professor Stephen Duffy, Emeritus Professor of Cancer Screening, Queen Mary University of London (QMUL), said: “It is not clear from the abstract exactly when the food frequency questionnaires were administered, but it does appear that this was after diagnosis with lung cancer.
“Is it possible that there is an element of reverse causality here? That is, people with a diagnosis of a serious illness may make lifestyle changes in response, for example to a more healthy diet. Also, it appears that the comparison is with standards from an external study.”
He added: “Thus these results may be subject to confounding with factors related to the time of recruitment and other factors which differ between the two studies. I would certainly not advise against a healthy diet on the basis of these results.”
More broadly, other researchers noted the key limitation that a link does not automatically prove cause and effect. It’s possible that separate characteristics associated with healthier lifestyles could be influencing the results.
Prof Peter Shields, Emeritus Professor of Medical Oncology at Ohio State University, said: “It is well known that leanness is a risk factor for lung cancer, opposite to most other cancers. The authors may not be seeing anything more than this.
“More importantly, the grouping of those mutations together is arbitrary and unclear if they share the same carcinogenic pathways, versus those are the only ones we know how to treat. And, even more important, a role for pesticides is entirely speculative.
“This research should be considered exploratory, as it is in early stage, and is a small study.”