Healthy Diet Linked to Early-Onset Lung Cancer: New Research Findings

A new study presented at the American Association for Cancer Research’s annual meeting has found a surprising association between higher diet quality and increased risk of early-onset lung cancer in adults under 50, challenging long-standing public health guidance that emphasizes fruits, vegetables, and whole grains as protective against cancer.

The research, part of the Epidemiology of Young Lung Cancer Project, analyzed dietary recall from 187 individuals diagnosed with lung cancer before age 50. Using the Healthy Eating Index (HEI), a validated measure of diet quality aligned with federal dietary guidelines, researchers found that these patients had an average HEI score of 65 out of 100 — significantly higher than the national U.S. Average of 57. The patients reported consuming more servings of dark green vegetables, legumes, and whole grains than the general population, averaging 4.3 and 3.9 servings per day, respectively, compared to 3.6 and 2.6 among U.S. Adults overall.

Most participants in the study had never smoked, and their lung cancers were of a type not typically associated with tobacco use. A majority carried an EGFR mutation, a genetic alteration increasingly linked to lung cancer in younger, non-smoking individuals. While smoking was reported in about 40% of the cohort, the study’s focus was on non-smokers or light smokers, reflecting a growing epidemiological trend of lung cancer arising in younger adults without traditional risk factors.

The findings have prompted scientific discussion about potential explanations, with the study’s lead author, Jorge Nieva, MD, a medical oncologist at USC Norris Comprehensive Cancer Center, suggesting that pesticide residues on fruits, vegetables, and grains could be a contributing factor. “There is an epidemic of lung cancer in young, nonsmoking people in the United States, and we need to make efforts to understand what is causing it,” Nieva said. “Something about their diet might be contributing to it.” He noted that agricultural workers exposed to pesticides show elevated lung cancer risk, raising the possibility that dietary intake of contaminated produce could play a role in susceptible populations.

However, experts have urged caution in interpreting the results. Katrine Wallace, PhD, an epidemiologist at the University of Illinois School of Public Health, described the evidence as “low-level” and emphasized that the study only shows correlation, not causation. “This is hypothesis-generation and not ready for prime time,” Wallace said. “The message is problematic because it could mislead the public and undermine well-established dietary guidance.” She pointed out that individuals diagnosed with cancer may alter their recall of past behaviors, potentially inflating reports of healthy eating as they seek explanations for their illness.

Roberto Pili, MD, associate dean for cancer research at the University at Buffalo Jacobs School of Medicine, echoed these concerns, noting that higher HEI scores have consistently been linked to reduced risk of chronic diseases, including colon cancer. “A higher Healthy Eating Index reported in this patient population, actually, has been associated with reduced risk of chronic diseases and cancer, in particular colon cancer,” Pili said. “there is a recognized protective impact of eating more fruits and vegetables.” He added that while the pesticide exposure hypothesis is “reasonable,” there is currently no biological evidence — such as measured pesticide levels in blood or urine — to support it in this cohort.

Sora Ely, MD, a lung cancer researcher at George Washington University School of Medicine, highlighted recall bias as a key limitation. “We have all seen patients — particularly those who feel they are out of the normal demographic for a form of cancer — who are searching for reasons they may have gotten cancer, even if there is no reason,” Ely said. “The thought is often, ‘If I did something that caused this, there may be something I can do to help the outcome.’” This psychological tendency may lead patients to overreport healthy behaviors after diagnosis, distorting retrospective dietary data.

Ely also noted that individuals who volunteer for such studies may already be more health-conscious, further skewing the sample toward higher diet quality scores regardless of disease status. “The results only show that lung cancer patients reported slightly healthier diets than national averages,” Wallace reiterated. “This observation does not support the claim that higher consumption of fruits, vegetables, or whole grains increases lung cancer risk.”

Despite the unexpected association, medical experts agree that current dietary guidelines should not be changed based on this study. Ely emphasized that she would not alter her own diet or advise patients to do so based on these findings. “The possibility of bias playing a role is enough that I’m not going to change my diet, and I’m not going to recommend that my patients do either,” she said.

Pili called for larger, prospective studies that could better assess dietary exposures and potential contaminants, including pesticide levels in biological samples. “Regardless of whether the produce is organic or conventional, washing should always be recommended to reduce contaminants such as chemicals and bacteria,” he said. Nieva echoed the need for continued investigation into the rising incidence of lung cancer in younger adults. “We need to stop ignoring the problem and conduct more research into the cause,” he stated.

For now, the study serves as a reminder of the complexities in nutritional epidemiology and the importance of distinguishing between association and causation. While healthy eating remains a cornerstone of cancer prevention for many malignancies, the biological mechanisms underlying early-onset lung cancer in non-smokers are still not fully understood. Ongoing research into genetic, environmental, and lifestyle factors — including potential foodborne exposures — will be essential to clarify risk and guide future public health recommendations.