As broad questions of reviews may be addressed by large sets of heterogeneous studies, the data synthesis may be particularly challenging. In our study, 9 reviews (among the 39 broadly focused reviews) pooled the results of different herbs, which did not identify potentially important differences in effects across different interventions. Systematic reviews can, but do not have to use meta-analysis when combining data from primary studies, prior to conducting a meta-analysis, reviewers should examine the consistency of the interventions. It is recommended that the data of each intervention should be analyzed and presented separately if several different interventions for the same condition were tested in one review.