Dietary risk factors for lung cancer: an umbrella review of systematic review and meta-analysis

Background: This study evaluates the methodological quality, bias, and reliability of evidence related to dietary risk factors for lung cancer through an umbrella review and provides a comprehensive overview of the identified risk factors.

Methods: This review protocol has been registered on PROSPERO. A systematic search was conducted in PubMed, Embase, Web of Science, and Cochrane Database of Systematic Reviews to collect meta-analyses on dietary factors and lung cancer risk published up to March 2026. The methodological quality of the included studies was evaluated using the A Measurement Tool to Assess Systematic Reviews (AMSTAR) tool, and the evidence strength of each outcome was rated based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system.

Results: There were 57 meta-analyses included, covering 57 diet-related factors. The association between folate and reduced risk of lung cancer is supported by moderate-quality evidence, while most other factors (such as beta-carotene, red and processed meat, etc.) have low or very low quality evidence. A healthy dietary pattern is associated with a lower risk of lung cancer risk, while a Western/meat diet pattern and a high glycemic load diet are positively associated with risk. Conclusion: The quality of evidence for the association between most dietary factors and lung cancer risk is low, with only folate showing moderate-quality evidence, indicating that current research is not sufficient to support strong causal inference. In the future, it is necessary to conduct well-designed prospective cohort studies and randomized controlled trials to provide a higher-quality scientific basis for precise nutritional prevention of lung cancer.