I find that doing a liver flush, plus the colon flush that goes with the Liver Flush helps prevent the headaches and other symptoms of detox that so often accompanies the first few days of fasting. It simply allows the liver to better process the toxins released through the MC. It is optional, but very helpful. If people would take a couple of weeks to prepare for the Master-Cleanse including weaning off sugar, wheat and caffeine, plus cleaning out the colon and gallbladder, they will not have such severe detox symptoms the first few days of the cleanse.