There are two ways to go on a cranberry juice diet: one way is to incorporate the juice into the normal daily diet and the other is to only drink cranberry juice for one to three days. The latter method is one of detoxification, which increases the metabolism and converts fats into energy. When the juice is fresh and made from the whole berry, the health benefits include the reduction of E. coli and other harmful bacteria, the destruction of various strains of virus, prevention and treatment of urinary tract infections, digestive health, and the promotion of good cholesterol over bad.
A cranberry juice diet involves the drinking of six 8 ounce (237 milliliters) glasses a day. It is recommended, however, that this be done for no longer than three days. The only other liquid allowed in this type of fasting is water, of which at least six glasses must also be consumed. The diet should be stopped with the onset of any side effects such as headache, diarrhea, abdominal bloating or pain.
Before starting on the fast, medical advice should be sought, as some medications and diseases may interact with the juice in a negative way. It is recommended that the cranberry juice fast be followed only during the spring or summer, when the body does not need energy to keep warm. The fast does have its detractors, however, as some experts maintain that any sort of liquid diet is bad for the body in that it causes depletion of nutrients and weakens the immune system, leaving it vulnerable to infection and inflammation.
Preparation for the cranberry juice diet means reducing and even eliminating alcohol, nicotine, caffeine and sugar for at least a week before the diet begins. Fatty foods and dairy products should also be severely limited. When done correctly, this diet leads to weight loss as long as care is taken after the diet to limit calorie intake.
Fasting and detoxifying by drinking only juice for a day or two is also considered by some as an ideal way of preparing the body for a weight loss diet. Cranberries are rich in antioxidants, vitamin C and dietary fiber. They contain compounds that inhibit the bacteria responsible for urinary tract infections, ulcers and gum disease. It is not necessary to follow the extreme form of the cranberry juice diet to receive these benefits, however, as the incorporation of even one glass a day can be advantageous.