Healthy diet, higher lung cancer risk? Deciphering surprising link in new study

Fruits and vegetables don’t cause lung cancer, but a new study may explain why scientists found a link. Lucas Ottone/ Stocksy A new study from USC researchers found an association between healthier diets containing fruits, vegetables, and whole grains and higher rates of early onset (or young-onset) lung cancer in nonsmokers.

The researchers believe that pesticide residue may be a possible explanation for this association, and not healthy foods themselves, and plan to investigate it further. They also found a similar association with women who take oral contraceptives.

While lung cancer mortality in the United States has declined significantly since 1990, incidence trends have been more nuanced. New lung cancer cases have fallen in men since the mid-1980s and in women since the mid-2000s, declining annually by 3.0% and 1.4%, respectively, from 2012 to 2021.

However, while overall incidence has gone down, researchers are concerned about a different trend: increasing lung cancer rates in younger nonsmokers, especially women. Researchers in the new study utilized data from the Epidemiology of Young Lung Cancer case study to examine this trend more closely.

They found a surprising association between healthier eating patterns and early onset lung cancer among nonsmokers. This finding is only an association, however, and does not prove that eating vegetables, fruits, or whole grains causes cancer.

The authors suspect environmental factors may contribute to this. The researchers presented the study findings at the American Association for Cancer Research annual meeting .

The results of the study are yet to be published in a peer-reviewed scientific journal. Exploring young-onset lung cancer While lung cancer typically affects older adults who have a background of smoking , it can still affect younger adults, including nonsmokers.

The average age of receiving a lung cancer diagnosis is 70, and when someone receives a diagnosis before the age of 50, it is referred to as “young-onset lung cancer.” Newer studies found an increase in young-onset lung cancer incidence among nonsmokers, which prompted the researchers of the new study to further examine what may be behind this. The researchers analyzed data from the Epidemiology of Young Lung Cancer study, which is a nationwide observational study that examines factors linked to cancer mutations.

The study group included 187 patients with young-onset lung cancer, and women accounted for 78% of the cohort. The scientists grouped the participants based on the biological pathways driving their tumors: the EGFR pathway group (73) the fusion-positive group (82) the mixed mutations group (32) Next, the researchers gathered epidemiological survey data covering the year before diagnosis.

This included information such as smoking history, oral contraceptive use, and demographics. They also reviewed dietary habits, which were assessed using food-frequency questionnaires.

The researchers assessed overall diet quality using the Healthy Eating Index (HEI); higher scores indicated healthier diets. Could pesticides explain the link between fruit, vegetables, and cancer?

The researchers reported that the majority of the participants of each group had never smoked. Prior smokers accounted for 32.9% of the EGFR pathway group, 13.4% of the fusion-positive group, and 21.9% of the mixed group.

Of the nonsmokers with young-onset lung cancer, the researchers found a surprising association between dietary choices and risk. Using the HEI, researchers found that the EGFR and fusion-positive groups had higher-than-average food scores, around 65% for each group.

Compared to the average U.S. adult’s HEI of 57, this is roughly a 13% difference.

All groups also consumed more servings of dark green vegetables, legumes, and whole grains compared to the average adult. While this association is surprising, it should not be interpreted to mean that healthy foods cause cancer.

The researchers say this points to the need to learn more about the environmental factors involved in growing the food. Jorge Nieva , MD, a medical oncologist and lung cancer specialist with USC Norris Comprehensive Cancer Center and lead author of the study, spoke with Medical News Today about the findings.

“There is a lot of work to be done, from measuring pesticide metabolites in lung cancer patients, to looking at different geographies and relative uses of different specific chemical substances,” said Nieva. Nieva pointed out that since all pesticides are not the same, they will need to understand the biological effects of each one.

Contraceptives may explain lung cancer risk Another interesting finding was that oral contraceptive use was notably higher than average among female participants in two groups. Around 11.4% of women ages 15 to 49 in the U.S.

report using oral contraceptives, which is significantly lower than the rate of the female study participants who took oral contraceptives. The EGFR and mixed mutation groups stood out, as around 77% of the women in these groups reported ever taking oral contraceptives.

Around 65% of the fusion-positive group reported taking them. As with the healthy eating pattern association, this does not show that oral contraceptives cause lung cancer, but it does open the door to another pathway to explore to figure out why young-onset lung cancer cases are increasing, particularly in women.

Nieva also touched on why women seemed more affected. He said that the mutations that contribute to young-onset lung cancer are more common in females.

Notably, the “most common subtype, EGFR, more commonly expresses estrogen receptors, particularly in women.” Nieva further talked about how chemicals that disrupt the endocrine system are used in pesticides . “In our study and for the U.S.

on average, women seem to have much healthier diets than men, and this might mean greater relative exposure to any contaminants that may be in whole grains, fruits and vegetables,” Nieva explained. Proceed with care in interpreting these findings David Yashar , MD, a hematologist-medical oncologist at MemorialCare Cancer Institute at Long Beach Medical Center, spoke with MNT about the study findings.

“In general, these are fascinating findings; however, I think we must be careful in the way we analyze the data,” said Yashar. Yashar said results do not suggest that fruits, vegetables, or whole grains alone increase lung cancer risk.

“It may be the link between pesticides that they use in growing the produce and whole grains that is the cause for increased rates of lung cancer in non-smoking females,” Yashar theorized. Yashar also pointed out that even if someone is concerned about the findings, practicing healthy eating habits is still crucial to overall health.

“We know that a poorer diet leads to obesity, and this also has a negative impact not only on one’s health, but also on the development of other cancers, such as breast cancer,” shared Yashar.