Any experienced traveller will likely have experienced some, ahem...unpleasant reactions to the local cuisine.
At best this is an inconvenience, at worst it can knock precious days off your trip.
But the cause of these gastrointestinal woes is often quite counterintuitive, and sometimes rooted in a lot of foods you would consider healthy back home. Fortunately, with a little knowledge preventing traveler's diarrhea is pretty easy,
The first thing to take into consideration is where you are travelling. Northern and Western Europe, Australia, North America and Japan have stringent food handling and safety laws.
In these places, food is unlikely to be left for long in the “danger zone” of between 5 to 60 °C, which is where food borne bacteria can grow. Also, the water quality is generally quite good and the heartier amongst you can get away with drinking local tap water.
Once you get out of these countries, the risks mount substantially.
In hot, equatorial regions like Southeast Asia, Latin America and Africa there is a lot more biology going on in general, and this increases the likelihood of ingesting weird bacteria.
The first and most common error is drinking sketchy water. The general best practice is to drink bottled water. But the problem is, none of the locals are drinking bottled water and it is not always available, especially outside of tourist areas.
In these situations the healthiest choice is, oddly, drinking soda pop. Even in the most far flung corners of the world Coke, Fanta and other sodas are ubiquitous. And since they are carbonated and acidic, bacteria simply cannot grow in them. For an extra layer of safety, take a tissue or hanky and wipe around the mouth of the bottle before drinking. Beer is also an option and commonly available, but often served warm and can exacerbate dehydration.
(These tips apply to trips lasting less than two to four weeks. If you are intending to stay for a period of months, slowly start introducing local tap water. After a year straight in Kenya, my stomach was bulletproofed to the point where I could drink Nairobi city tap water and even rainwater without any problems. This impresses and builds rapport with the locals because you’re not asking for any special treatment.)
When it comes to food, thou shalt always heed the prime commandment: “Boil It, Peel It, Cook It or Forget It.”
All salads are off limits, because they will have been washed with local water. Previously peeled fruit and fruit salads should be avoided as well. Also, beware of meat-and-rice dishes or samosas that have been sitting out.
Fortunately, all fresh prepped-in-front-of-you BBQ is good to go, as are freshly made burrito type street foods in Latin America. Noodle soups in Asia are a reliable winner as well. Rice and curries are a safe bet, as are fried foods. Cooked vegetables served hot are a reliable winner too, especially in Asia. Kale is also very common in Africa. It’s safe when cooked and is an extremely nutritious and hearty food packed with much-needed vitamins.
Abide these rules, and you should be fine.
My final final tip is to carry rehydration salts with you. Buy these at the pharmacy before you leave, and thank me later. These are basically concentrated electrolyte salts (similar to Gatorade), and can be dissolved into water. Oral Rehydration Therapy has been used to treat diarrhea for a hundred years, and are also useful in preventing heatstroke. If you have spent a long day in the sun, or hiking in a hot climate, these are a godsend.