Mediterranean diet adherence and dietary fat intake in relation to lung cancer outcomes: a prospective cohort study

Background: Lung cancer continues to be the most frequently diagnosed malignancy globally and a major contributor to cancer-related deaths. Although dietary factors have been increasingly implicated in its development, evidence for the Mediterranean diet (MED) and specific fat subtypes remains limited. Objectives: To examine the associations between MED adherence and dietary fat intakes with lung cancer incidence, mortality, and survival. Methods: We included 191 139 cancer-free participants from the UK Biobank. The validated Oxford WebQ 24-hour dietary questionnaire was used to measure dietary intake. The adherence of MED was assessed by the Alternate Mediterranean diet (AMED) score. Total dietary fat and fat subtype intakes were calculated as a proportion of total energy intake. Associations between dietary factors and lung cancer outcomes were analyzed using adjusted Cox regression. Results: After full adjustment, greater adherence to the MED was associated with a lower lung cancer risk (HR_{Q4 vs. Q1}: 0.66; 95% CI: 0.58-0.77), and lower lung cancer-specific mortality (HR_{Q4 vs. Q1}: 0.61; 95% CI: 0.50-0.74). Higher polyunsaturated fatty acids (PUFAs) intake was linked to lower lung cancer risk (HR_{Q4 vs. Q1}: 0.82; 95% CI: 0.71-0.95) and mortality (HR_{Q4 vs. Q1}: 0.77; 95% CI: 0.63-0.94), whereas higher saturated fatty acids (SFAs) intake was associated with increased lung cancer risk (HR_{Q4 vs. Q1}: 1.25; 95% CI: 1.09-1.45) and mortality (HR_{Q4 vs. Q1}: 1.23; 95% CI: 1.01-1.49). In isocaloric substitution analyses, replacing 1% of energy from SFAs with PUFAs was associated with a 9% and 10% lower risk of lung cancer incidence and mortality. Among participants who developed lung cancer, individuals with high pre-diagnosis AMED scores and PUFAs intake had better post-diagnosis survival than those with low AMED scores and low PUFAs intake (HR = 0.77; 95% CI: 0.61-0.96). Conclusions: Adherence to the MED and higher PUFAs intake were independently related to lower risk of lung cancer and reduced lung cancer-specific mortality. The combination of greater MED adherence and higher PUFAs intake may provide additional benefits for lung cancer post-diagnosis survival. These findings imply that dietary modifications might have a role in both the onset and progression of lung cancer. Further studies are warranted to clarify the mechanistic pathways and inform the development of dietary recommendations.