Although this recent study cited below only partly bears this out, a high quality probiotic is the one thing I advise all my patients, family and friends take with them when they travel overseas.
Based on a meta-analysis of 34 randomized trials, probiotics reduced the incidence of antibiotic-related diarrhea by 52 percent. Generally, probiotics lowered the risk of diarrhea among adults (26 percent) and children (57 percent). However, probiotics didn't do nearly as much good for travelers' diarrhea, according to the study, reducing it only by 8 percent.
I suspect there are reasons for this discrepancy. For one, there are many brands on the market, but many of them contain insufficient quantities of bacteria. When treating acute infectious diarrhea, large therapeutic doses are required (typically an entire bottle over a day's time or about an eighth of a bottle every hour until the problem is resolved). Most often, the symptoms will subside within four hours.
Using a probiotic is one of the most amazingly consistent approaches to manage travelers' diarrhea I have ever seen. In addition to a lot of lousy products on the market, there are many good ones. One of the best ways to find a good one is to ask a trusted expert in a local health food store. If you don't have such a resource, or simply want to take advantage of the five years we spent researching this new product, you can consider Rebalanced Health Probiotics, a probiotic now available in my Web store.
The Lancet Infectious Diseases, Vol. 6, No. 6, June 2006: 374-382