Indole-3-carbinol: anticarcinogen or tumor promoter in brassica vegetables?

Indole-3-carbinol (I3C) is one of several compounds in brassica vegetables that demonstrate anticarcinogenic effects in experimental animals. A review of Medline and CancerLit databases indicated that interest in I3C, as a cancer chemopreventive agent, has increased significantly in the past 5-10 years. Whereas most studies report inhibitory or protective effects of I3C in vivo, a few provide clear evidence for promotion or enhancement of carcinogenesis, depending upon the initiator, exposure protocol and species. In the absence of detailed information on the inhibitory and in particular, promotional mechanisms, it would seem advisable to proceed with caution before including I3C in extensive human clinical trials.