Could Consumption of UPFs Up Lung Cancer Risk?

Medscape

a day ago

Individuals who ate more ultra-processed foods (UPFs) had a significantly higher risk for lung cancer over 12 years than those who ate fewer UPFs, based on new data from more than 100,000 adults in an observational study.
Cigarette smoking is a known contributor to lung cancer, but diet also is known to play a role; however, data on the impact of UPFs in particular on lung cancer risk remain unclear, Kanran Wang, MD, of Chongqing Cancer Hospital, Chongqing, China, and colleagues wrote.
In a study published in Thorax, the researchers reviewed data from 101,732 adults enrolled in the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, a randomized trial of screening tests for lung, prostate, colorectal, and ovarian cancers from 10 centers across the US. The primary endpoint was the incidence of lung cancer.
In a multivariate analysis, individuals in the highest quartile of UPF consumption were 41% more likely to develop lung cancer than those in the lowest quartile of consumption (hazard ratio [HR], 1.41); risk also was higher for both non-small cell lung cancer (NSCLC) (HR, 1.37) and small cell lung cancer (SCLC) (HR, 1.44). These results remained statistically significant after a large range of subgroup and sensitivity analyses, including age, sex, and family history of lung cancer.
UPF consumption was based on the Food Frequency Questionnaire, and foods were classified by dietitians into four categories of processing as unprocessed or minimally processed, processed culinary ingredients, processed foods, and UPF, based on the NOVA criteria. The mean age of the study population at baseline was 62.5 years. The mean energy-adjusted UPF consumption was 2.8 servings/d, with mean servings for the lowest and highest intake quarters of 0.5 and 6.0, respectively. Approximately half of the participants in each quarter were current or ever-smokers.
The researchers identified 1706 lung cancer cases over a mean follow-up of 12.2 years, including 1473 cases of NSCLC and 233 cases of SCLC.
Potential explanations for the association between UPF and lung cancer include the impact of nutritional components of UPF including high sodium, saturated fats, added sugar, and low fiber, the researchers noted.
Overall, lunchmeat was the greatest contributor to UPF (11%) following by caffeinated soft drinks (diet and regular) and decaffeinated soft drinks (diet and regular), which each accounted for approximately 7% of UPF intake.
The researchers acknowledged the study limitations, including the observational design, limited number of incident events, relatively homogenous study population, and use of self-reports.
However, they concluded that if the findings are confirmed in other studies, limiting trends of UPF intake globally could help reduce the overall burden of lung cancer. In addition, 'future studies should elucidate potential molecular mechanisms and increase understanding of the observed associations,' the researchers wrote.
Caveats Abound, Experts Say
Several experts weighed in with comments that were published online in the Science Media Centre.
Although the study was well-conducted, limitations include the study population of only adults aged 55-74 years in the US, therefore the results may not be relevant to younger individuals in other countries, said Rachel Richardson, acting head of methods support, The Cochrane Collaboration, in an editorial section accompanying the study.
In addition, dietary habits also change considerably over the course of long-term studies; therefore, 'it is difficult to directly conclude that lung cancer is related to the level of UPF consumption alone given it was only declared at the start of the study,' wrote Sam Hare, MD, a consultant chest radiologist at Royal Free London NHD Trust.
'The most obvious confounding factor here is smoking, which is well-known to cause a greatly increased risk of lung cancer,' wrote Adam Jacobs, MD, executive director and strategic consultant, biostatistics, Ergomed. 'If people with high UPF consumption smoked more than people with low UPF consumption, then that difference in smoking could easily lead to the observed results,' he said. The researchers' efforts to adjust for smoking was limited by the use of only two categories (current/former smokers and nonsmokers) and the use of self-reports, he said.
Study Has Merit, but More Work Is Needed
There was ample justification to conduct a study on the link between UPF and lung cancer, as prior evidence on this association was limited and inconsistent, said Jamie Garfield, MD, professor of thoracic medicine and surgery at the Lewis Katz School of Medicine at Temple University, Philadelphia, in an interview.
'Given the global rise in UPF consumption and the high burden of lung cancer, clarifying this relationship is important for public health and cancer prevention strategies,' said Garfield, who was not involved in the study.
Strengths of this study include the large, well-characterized population, pathologic confirmation of lung cancer, and comprehensive adjustment for confounders such as smoking, diet quality, and demographic factors, she said.
The findings of a statistically significant association between higher UPF intake and increased risk for lung cancer (including both NSCLC and SCLC), were not surprising, as similar associations have been observed for other cancer types and chronic diseases, Garfield told Medscape Medical News .
'However, the magnitude and consistency of the association across subgroups, and the observation that the risk persisted after adjustment for smoking and diet quality, are notable and reinforce the plausibility of a direct link,' she said.
The findings were limited by the observational design that prevents conclusions of causality, especially from unmeasured smoking intensity, said Garfield. Additionally, the single dietary assessment at baseline only may not capture dietary changes over time and could lead to misclassification of UPF intake bias, she noted.
Other limitations included the use of a validated food frequency questionnaire not designed to align with the NOVA classifications, and the use of a mainly non-Hispanic White study population, Garfield said.
Despite the limitations, the study findings are worthwhile and have potential implications for clinical practice, Garfield told Medscape Medical News . 'They support dietary counseling to limit UPF intake as part of cancer prevention,' she said. However, 'Further research in more diverse populations and with repeated dietary measures is needed to confirm causality and clarify mechanisms,' she added.
This study was funded by the Chongqing University Cancer Hospital, Chongqing, China, and received grants from the Chongqing Talent Plan, Chongqing Shapingba District Technological Innovation Project.
The researchers disclosed no financial conflicts of interest.
The Science Media Centre commentators disclosed no financial conflicts of interest.