Beyond supplements and surrogates: an evidence-quality map informs a strategic rebalancing of dietary research in prostate cancer active surveillance.

Background: Evidence regarding whether dietary interventions can delay disease progression in men undergoing active surveillance for prostate cancer remains fragmented. This study innovatively combines a systematic review of the evidence with rigorous methodological assessment, aiming to provide a critical analysis of the evidence base in this field, rather than merely a descriptive review. Methods: We searched the PubMed, Embase, Cochrane Library, and Web of Science databases, mapping interventions to outcomes. An evidence bubble plot was constructed, with the bubble size representing the number of studies and the color intensity representing the proportion of randomized controlled trials. Methodological quality were assessed using the Cochrane risk of bias tool, ROBINS-I, the Newcastle-Ottawa Scale and the JBI tool. Results: The map revealed a dense but flawed evidence cluster focused on phytochemical-rich supplements and PSA/biomarker change, primarily supported by randomized controlled trials with prevalent limitations in blinding and randomization reporting. In stark contrast, there is a critical gap in the evidence from intervention studies assessing the impact of holistic dietary patterns on clinical progression endpoints. The integrated quality assessment underscores a fundamental mismatch: while abundant, research on supplements is often methodologically compromised, conversely, the few observational studies on holistic dietary patterns, although of higher quality, are unable to establish causality. Conclusion: Current evidence is misaligned with clinical needs, being rich in low-certainty supplement data but scarce in high-quality trials on holistic diets. Future research would benefit greatly from a strategic reorientation of funding-namely, prioritizing large-scale, rigorous clinical trials to evaluate comprehensive dietary interventions targeting clinically significant disease progression endpoints, while recognizing that supplement studies continue to play an important role in generating mechanistic hypotheses. Systematic review registration: https://doi.org/10.17605/OSF.IO/T8G97.