I think it's the cayenne. My husband and I did this fast a couple of years ago, but for some reason, I thought that the cayenne was optional. I tried it, didn't like it and just left it out. So, we got through the fast just fine...did it for eight days, but I don't know how effective it was without the cayenne. The memory of that stuff coming back up is still too fresh in my memory so I'm not about to touch it in any way, shape or form for awhile. I'll look for a nice juice fast.