I'm going to add to it though, that even though there really isn't a special diet you need to be on
The lighter and healthier you eat before an ayahuasca session, the easier the purge will be. My first time I drank nothing but water all day, and only ate a cup of ramen noodles. The purge took less than two minutes, and didn't hurt at all.
My second time, I paid no attention whatsoever to my diet, and drank the medicine after a normals days worth of eating. Some junk food, some snacks, pop, etc. The purge was waaaaaaayyyy more hardcore, and I ended up with dirrahea too.
So just keep that in mind, and godspeed.