Sustainable diets and cancer: a systematic review and meta-analysis

Background Modern food systems contribute to environmental degradation, while prevailing unhealthy eating behaviours exacerbate the global cancer burden, creating a dual synergistic crisis for both planetary and human health. Investigating the impact of sustainable diets on cancer is therefore essential. Methods Following the 2020 PRISMA guidelines for reporting systematic reviews and meta-analysis, observational studies on cancer incidence and mortality among adults, assessing the sustainability of their diets using various metrics, were examined. Effect measures were pooled to compare the highest versus lowest adherence to sustainable dietary patterns. Summary effect estimates for cancer incidence and mortality were calculated using random-effects models. Subgroup analyses were conducted by sex, geographical region, study design, sustainability metric used, dietary assessment indexes reflecting sustainability, and cancer type. E-values were used to evaluate the robustness of associations against potential unmeasured confounding. The study was pre-registered in PROSPERO (ID CRD42024545102). Findings 19 effect estimates from 17 studies, encompassing over 2·2 million participants, revealed a significant reduction in cancer incidence (hazard ratio 0·93, 95% CI 0·88−0·98, I 2 84·67%) and cancer mortality (hazard ratio 0·88; 95% CI 0·85–0·92, I 2 21·25%) associated with higher adherence to sustainable diets. Subgroup analyses indicated that the overall effect was modified by study design, sustainability metrics, and dietary assessment index. Interpretation These findings support evidence linking sustainable diets with reduced cancer incidence and mortality, underscoring their potential role in cancer prevention while providing concurrent environmental benefits. The notable variability in sustainability metrics highlights the need for standardised approaches in future research.