NR4A1 and breast cancer: In light of the methodological and research gaps identified in our review (e.g., consideration of different sources/subtypes of dietary iron intake, comprehensive assessment of supplemental and total iron intake, repeated measures of iron intake/status at multiple time points, exploration of nonlinear trends, stratification of results by menopausal and hormone receptor status), further research is needed to better elucidate the association between iron intake/status and risk of breast cancer.