This is the answer I got re taking Inner Health Plus to stop Bali Belly - 'When there are adequate "good" bacteria in the intestines there is nowhere for the "bad" bacteria to adhere to the bowel wall, therefore they cannot infect you. You also have improved natural immunity to fight off the baddies' - they also told me that it has to be taken for at least 3 weeks prior to departure, during the holiday and a couple of weeks after. Hope this answers everyones questions. If you need anymore help, please don't hesitate to ask.
Cheers
Robin