Study selection
Our objective was to thoroughly evaluate the relation between dietary intake or blood concentrations
of α-carotene, β-carotene, lycopene and risk of PCa. Studies that met the following
criteria were included in the meta-analysis: 1) used epidemiologic investigation design: casecontrol
study, nested case-control study, cohort study, etc; 2) evaluated the association between
carotene(α- and/or β-), lycopene and PCa risk; and 3) provided RRs with 95% CIs for 3 exposure
categories. Furthermore, studies that additionally provided the doses of carotenoids, the
number of cases, and the number of controls(or person-years) in each of exposure categories
were included in the dose-response meta-analysis.