A comprehensive meta‐analysis on dietary flavonoid and lignan intake and cancer risk: Level of evidence and limitations

Most evidence reported in previous meta-analyses was driven by case-control studies. Overall results may be promising but are inconclusive. Further prospective cohorts assessing dietary polyphenol exposure and studies using other methods to evaluate exposure (i.e. markers of consumption, metabolism, excretion) are needed to confirm and determine consumption levels required to achieve health benefits.