When thinking about lung cancer, most people still imagine heavy smokers and the elderly. But in recent years a phenomenon has been unfolding that engages researchers worldwide: more and more young people who have never smoked are being diagnosed with the disease, particularly women. Despite the ongoing decline in smoking rates, the number of cases in this population is rising - and the reason remains unclear.

A new study from the United States now suggests a possible and surprising direction. The researchers found that young people who developed lung cancer despite never having smoked actually reported a healthier-than-average diet, including more fruits, vegetables and whole grains. According to the researchers, the foods themselves are not dangerous; rather, exposure to pesticide residues that may be present on them could play a role.

The study, presented at the annual meeting of the American Association for Cancer Research (AACR), suggests that exposure to pesticides may explain at least part of the findings, though the researchers emphasize that the possible link still requires further investigation.

The researchers note that fruits, vegetables and whole grains grown in conventional agriculture typically contain more pesticide residues than dairy products, meat and processed foods. They also cite previous studies showing that agricultural workers with years of exposure to certain pesticides face an elevated risk of developing lung cancer.

Dr. Haim Zilberman, Head of Lung and Chest Tumors at the Oncology and Hematology Center at Haemek Medical Center, part of Clalit, says: "There are data from studies conducted among agricultural workers indicating that prolonged exposure to certain types of pesticides may increase the risk of lung cancer. Such exposure may also contribute to some young patients, but it is important to note that the current study included a relatively small number of participants, so larger studies are needed to examine whether such a link exists."

The study involved 187 people diagnosed with lung cancer before age 50 as part of the Epidemiology of Young Lung Cancer project. Participants provided information on their dietary habits, smoking history, demographic data and disease characteristics.

Most participants had never smoked, and many were diagnosed with a biologically distinct type of lung cancer from that seen in smokers. A previous study by the same research group suggested that lung tumors developing in young people may represent unique subtypes of the disease.

To assess diet quality, the researchers used the Healthy Eating Index (HEI), which assigns a score from 1 to 100 based on American dietary guidelines. The average score among study participants was 65 points, compared with an average of 57 in the general American population. In addition, participants reported higher consumption of fruits, vegetables and whole grains.

On average they consumed 4.3 servings per day of dark green vegetables and legumes and 3.9 servings of whole grains. By comparison, the general population averages 3.6 servings of dark green vegetables and legumes and 2.6 servings of whole grains daily.

Another notable finding was the difference between women and men. The researchers found that women under 50 who had never smoked were diagnosed with lung cancer at a higher rate than men in the same age group. These women also reported, on average, a healthier diet that included more fruits, vegetables and whole grains.

According to Dr. Zilberman, pesticides are only one of the possibilities currently being examined. "There are additional risk factors that may be linked to the development of lung cancer in non-smokers, including exposure to environmental pollutants, harmful substances in the workplace, radon gas - a naturally occurring radioactive gas that can accumulate in homes and buildings - and secondhand smoke."

Alongside the findings, the researchers highlight significant limitations of the study. Chief among them is that they did not measure pesticide levels in participants' bodies but instead estimated exposure based on prior data on residue concentrations in different food groups.

They say the next step will be to directly measure pesticide levels in blood and urine samples from patients to determine whether specific substances may be associated with increased lung-cancer risk.

According to Dr. Zilberman, there is currently no reason to change dietary recommendations based on the study. "The important message is that even young people who lead a healthy lifestyle should listen to their bodies and not ignore unusual symptoms. A new cough that persists over time without explanation, unplanned weight loss or other ongoing symptoms are reasons to see a doctor and get checked."