Prune juice can take as little as a day to as much as several days to have an effect on the bowels. Up to 4 ounces of prune juice can be consumed daily to promote a healthy bowel movement. This level should not be exceeded for quicker results.
Excessive intake of prune juice can cause cramping and other digestive distress, such as loose bowel movements. Drinking prune juice, along with drinking plenty of water and getting regular exercise, is helpful in maintaining healthy bowel function. While 4 ounces of prune juice is a standard guideline, an individual's doctor may suggest slightly increasing consumption over time if the individual can tolerate more.