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

BACKGROUND: Lung cancer poses a substantial global public health burden, and dietary factors represent potentially modifiable targets for primary prevention. This study evaluates the methodological quality, risk of 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. CONCLUSIONS: 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.