“The concern is traveler’s diarrhea, which can be brought on by exposure to microbes that we are not used to,” Dr. B. says. “In these places, the local people are used to them, but we’re not exposed, so we are not used to them. It’s likely the water is not treated the same way in other places as we treat our water in the United States. Like E. coli…every ounce of water has a percentage of the bacteria, if you ingest enough of it, it crosses a line and gives you traveler’s diarrhea.” One of the purposes of our gut microbiome is to protect us from this bacteria. For example, when we take antibiotics, we can be prone to new infections developing, for example a bacteria called C. diff grows because we have suppressed the good bacteria that usually keeps it in check.

So, follow the travel food safety advice of the CDC: “Avoid eating raw meat or seafood, including items “cooked” with citrus juice, vinegar, or other acidic liquid (such as ceviche).” That’s because all these ingredients have not been basically sterilized by fire, ie cooked. (That’s a lesson I won’t soon forget after losing 5 pounds in two days after eating a large plate of steak tartare at an outdoor café in the south of France.)