GI problems can occur for a lot of different reasons while traveling in Mexico, but they are easy to avoid.

Most people are aware of gastrointestinal issues related to going to Mexico. “Montezuma’s Revenge” as dubbed by Americans—diarrhea caused by drinking tainted water or food. This is often caused by eating food that's got bacteria on it, such as e. coli. Native Mexicans may be immune to it, but Americans are susceptible to sickness caused by these bacterias.

Keep in mind that it is actually vegetables, particularly raw vegetables like lettuce, and fresh fruits like strawberries, which when unwashed and uncooked can likely carry bacterias. When foods are cooked, like meat, bacteria is killed. For gastrointestinal issues, be very careful of raw toppings and raw sauces at street food vendors. Avoid those food which have been sitting in the sun in plastic containers—if they weren’t properly washed, they may be full of harmful bacteria. But at any nice, sit down restaurant that you go to, you should be fine eating vegetables and sauces.

Sometimes people get sick because the street food can be heavy in fat or heavy in salt. Just like in the United States that you get sick after eating a footlong chili cheese dog, all the grease and sodium in a street food burrito may disagree with you. There's a lot of lard in street food, and your body may not be used to having that much pork fat. Which can also cause GI problems.

What you should do to prepare and protect your stomach is this: Take Pepto Bismol chewable tablets every single day. Just one or two in the morning should coat and protect your stomach from irritation. Do not buy the generic Pepto Bismol chewable tablets because they taste very, very bad. If you eat a heavy meal later in the day, you may want to have another tablet. Pepto will calm your stomach, so things like pork fat or too much salt won’t bother it so much.

I recommend that you take probiotics for at least a week before you go to mexico and take them while you're there. By making sure your belly is full of good bacteria, it will help mitigate any problems with bad bacteria you may ingest that your body is not be used to.

FINALLY: When brushing your teeth always use bottled water! Make sure not to rinse your toothbrush and mouth out with water from the tap, as this may make you sick.