Indole-3-carbinol (I3C) is derived from the breakdown of glucobrassicin, a compound found in cruciferous vegetables.
In the stomach, I3C molecules undergo acid-catalyzed condensation that generates a number of biologically active I3C oligomers, such as 3,3′-diindolylmethane (DIM). DIM and I3C come from the same source, and the majority of I3C is converted to DIM. However, DIM and I3C are different molecules with different (albeit similar) chemical structures.
Why choose DIM over I3C?
In terms of a dietary supplement, the benefits for I3C and DIM are similar, most likely because of the high rate at which I3C converts to DIM. However, DIM tends to be the preferred supplemental form because of the relative instability of I3C and its conversion to other molecules whose biological actions are not well studied. When you supplement with DIM, you are going straight to the active molecule without waiting for your body to first complete all of the conversion steps.
What is the link with genetics?
DIM upregulates CYP1A1 and downregulates CYP1B1 and CYP19A1. For someone who has a slower CYP1A1 variant or a faster CYP1B1 or CYP19A1 variant, DIM is really good.
The CYP1A1 enzyme levels rise and fall over the course of a day along with the core circadian gene, CLOCK. Taking DIM in the morning may be more effective than taking DIM at night.
If people aren’t eating enough cruciferous veggies, DIM is a suitable alternative. Cabbage is the cruciferous vegetable highest in DIM.