Study Linking Fruits, Veggies to Lung Cancer Raises Eyebrows

SAN DIEGO — Outside experts expressed caution about a study suggesting a link between early onset lung cancer and diets rich in fruits, vegetables, and whole grains.

Survey data on 187 lung cancer patients ages 50 and younger with molecular subtypes of non-small cell lung cancer mostly seen in low-risk groups — such as women and non-smokers — revealed that these patients on average had higher-quality diets than the general U.S. population, based on Healthy Eating Index (HEI) scores.

The researchers suggested that components of these diets are those often exposed to pesticides, which could indicate a possible link to lung cancer.

“Lung cancer is not one disease,” said Jorge J. Nieva, MD, of the Keck School of Medicine at the University of Southern California in Los Angeles, part of the research team presenting the findings at the American Association for Cancer Research annual meeting.

“There’s a lot of lung cancer that’s being driven by things other than tobacco, and we need to stop ignoring the growth of non-tobacco-related lung cancer in the population,” he told MedPage Today.

Karla Giboyeaux, a clinical dietitian nutritionist at Memorial Sloan Kettering Cancer Center in New York City, noted that the study was “interesting, but we have to be really careful not to jump to conclusions.”

“It found that younger non-smokers with lung cancer reported slightly better diet quality — but that doesn’t mean fruits, vegetables, or whole grains are causing cancer,” she told MedPage Today.

“The idea that pesticides are responsible is still just a theory, since this study didn’t actually measure pesticide exposure,” she said. “What we do know, consistently, is that high-fiber diets including fruits, vegetables, and whole grains support overall health and are linked to lower risk of many chronic diseases, including several cancers. This is really a signal that more research is needed — not a reason for people to avoid fruits, vegetables, and whole grains.”

Urvi A. Shah, MD, also of Memorial Sloan Kettering Cancer Center, told MedPage Today that she and her colleagues found similar counterintuitive results in a study evaluating dietary patterns among patients with plasma cell disorders that showed that they had higher HEI scores than the general U.S. population.

“This is because of the biases of those who respond to such surveys, as well as the changes they make after their diagnosis, and cannot be attributed to the healthier diet causing the cancer,” she said. “Those who participate in studies are more aware of research and guidance on diet and likely have healthier diets.”

Shah had several other reservations about the study, including the fact that observational studies in larger cohorts, such as an analysis of U.K. Biobank participants, have shown a reduced risk of lung cancer in those with anti-inflammatory diets and diets rich in plant foods and low in meats.

She also noted that plant foods include dietary fiber and flavonoids, which have been shown to be significantly associated with reduced risks of cancer and chronic diseases, irrespective of adjustment for pesticide exposure.

Study Details

Nieva and colleagues analyzed 187 patients (78% women) from the Epidemiology of Young Lung Cancer observational case study, using mutation-based grouping by shared biological mechanisms — EGFR pathway, fusion positive (ALK+ROS1+RET+NTRK), and other/mixed mutations. The study uses comprehensive epidemiological surveys to capture smoking history, diet, oral contraceptive use, physical activity, and genomic alterations.

Based on HEI scores (a ranking of the overall quality of Americans’ diets on a scale of 1-100), Nieva and team found that young lung cancer patients had an average HEI score of 65 out of 100, compared with the national average of 57.

When looking at specific diet patterns, based on a 5-point HEI scale, compared with the general population, young lung cancer patients had significantly higher scores for:

• Total vegetables: 4.2 vs 3.5
• Total fruit: 3.3 vs 2.5
• Whole grains: 3.9 vs 2.6

What’s Causing Lung Cancer in Younger Adults?

“We launched this study to try to understand what were the potential epidemiologic factors that we might see in these young lung cancer patients,” Nieva said.

Lung cancer in patients 50 and younger is rare and biologically distinct, and mostly affects never-smokers with targetable mutations, including EGFR, ALK, and ROS1.

While the incidence has declined among men, it has increased among women, suggesting that “an alternative carcinogenic pathway may be driving disease,” Nieva said. “And what we found in the survey was that these people were actually super healthy people,” based on their diet histories and exercise patterns.

“And interestingly, when you look at healthy eating indexes in general, women are generally healthier than men, and that’s true in our lung cancer patient population, and that’s true in the U.S. population overall,” he noted. “So, at first we thought these people are eating healthy, that couldn’t be the problem.”

However, Nieva and colleagues also knew that studies have shown that occupational exposures to some pesticides may increase the risk of lung cancer among agricultural workers.

“So, what if diet actually is the problem?” Nieva asked. “When we see that people are eating more of the types of foods that are exposed to pesticides, and we see that agricultural workers who are pesticide sprayers have high lung cancer rates, it raises the question as to whether or not it could be a dietary source for a new carcinogen.”

However, Shah pointed out that the increased risk of lung cancer in agricultural workers involves a scenario of direct inhalation of pesticides. “So, it’s a stretch to conclude that pesticides in diet caused young lung cancer,” she said.

In any case, the potential link between pesticides and lung cancer needs more research, Nieva said. He and his colleagues did not test specific foods for pesticides, but used published data on average pesticide levels for food categories, such as fruits, vegetables, and grains, to estimate exposure.

The next step, said Nieva, will be to measure pesticide levels in patients’ blood or urine samples.