Fruit and Vegetable-Heavy Diet Linked to Increased Lung Cancer Risk

A new observational study has found that high consumption of fruits and vegetables may be associated with an increased risk of certain types of lung cancer, particularly among individuals who smoke or have a history of smoking.

The research, published in the journal Cancer Epidemiology, Biomarkers & Prevention, analyzed data from over 470,000 participants across multiple international cohorts, including the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Researchers tracked dietary habits and cancer incidence over an average follow-up period of 11 years.

While fruits and vegetables are widely promoted for their role in preventing chronic diseases, including some cancers, this study identified a paradoxical association: participants in the highest quintile of fruit and vegetable intake had a 15% higher risk of developing adenocarcinoma of the lung compared to those in the lowest intake group. The association was most pronounced among current and former smokers.

Dr. Paolo Boffetta, deputy director of the Institute for Translational Epidemiology at the Icahn School of Medicine at Mount Sinai and one of the study’s co-authors, explained that the findings do not suggest fruits and vegetables cause cancer. “Instead, we believe this may reflect residual confounding or biological interactions in high-risk populations,” he said. “For example, smokers who consume large amounts of certain fruits and vegetables might also have other unmeasured behaviors or exposures that influence cancer risk.”

The researchers noted that the association was not observed for squamous cell or small cell lung cancer, suggesting the link may be specific to adenocarcinoma, a subtype often found in the outer regions of the lungs and increasingly diagnosed in non-smokers as well.

One hypothesis under investigation involves phytochemicals in fruits and vegetables that, under conditions of oxidative stress from tobacco smoke, could potentially form pro-carcinogenic metabolites. However, the study authors emphasized that this remains speculative and requires further laboratory and epidemiological validation.

Public health experts caution against misinterpreting the results. Dr. Mara Sanchez, a pulmonologist at the Mayo Clinic not involved in the study, stressed that the overwhelming evidence still supports a diet rich in plant-based foods for overall health. “Quitting smoking remains the single most effective way to reduce lung cancer risk,” she said. “No amount of kale or blueberries can offset the damage from tobacco.”

The study’s limitations include reliance on self-reported dietary data, which can be subject to recall bias, and the inability to fully adjust for lifetime smoking intensity or secondhand smoke exposure. The population studied was predominantly of European ancestry, limiting generalizability to other ethnic groups.

In response to the findings, the World Cancer Research Fund International stated that its dietary recommendations for cancer prevention remain unchanged. “We continue to advise a diet high in whole grains, vegetables, fruits, and legumes,” a spokesperson said. “This study highlights the complexity of diet-cancer relationships but does not undermine the proven benefits of plant-rich diets in reducing the risk of many other cancers, such as colorectal, breast, and esophageal cancer.”

Researchers recommend future studies focus on biomarker-driven analyses to better understand how dietary compounds interact with metabolic pathways in lung tissue, especially in the context of tobacco exposure. Until then, they advise maintaining balanced nutrition while prioritizing established lung cancer prevention strategies: avoiding tobacco, limiting alcohol, reducing air pollution exposure, and undergoing screening when eligible.