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Pacifying Montezuma’s Revenge

Do probiotics and prebiotics placate the poops?

Study under review: Are probiotics and prebiotics effective in the prevention of travellers’ diarrhea: A systematic review and meta-analysis


Travelers' diarrhea (TD) is pretty much exactly what you think it is: the onset of diarrhea when traveling to another country, typically lower income countries located in Asia, Africa, or Latin America. Although diarrhea or other gastrointestinal problems can be caused by the stress of traveling, TD is most often caused[1] by microorganisms such as E. coli, Salmonella, or protozoa such as Giardia lamblia.

Although TD rates have fallen somewhat in recent decades, it still remains a common health problem among travelers, with incidence of TD[2] between 10-40% during the first two weeks of travel depending on the destination country. Risk of developing TD is considered high when the incidence is greater than 20% for the first two weeks of travel. Intermediate risk is considered 8-20% incidence, and low risk is less than 8%. Higher risk countries are shown in Figure 1, and include most of Central America and Africa, while countries such as China, Russia, and Brazil are considered to be intermediate risk. The United States, Canada, Australia and the majority of western Europe are considered low risk for developing TD.

Most cases of TD are caused by the ingestion[3] of contaminated food or beverages. According to a publication[4] by the Centers for Disease Control and Prevention, the contamination may be due to a variety of factors: inability to properly maintain cold temperatures of perishable product due to inconsistent electrical capacity and blackouts, inadequate water supply leading to poor handwashing practices or utensil cleaning, and warm climates may increase flying insect activity, which can lead to cross-contamination. Additionally, food vendors and preparers may lack the knowledge[5] of safe food practices, the local government may not have comprehensive food safety standards, or there may not be strict enforcement of the existing regulations. This is why it is recommended[6] for people who travel to countries at higher risk for TD to wash their hands often, consume water or other beverages in factory-sealed containers, eat fully-cooked food that has been recently prepared, and avoid fresh produce, undercooked meats, and tap water. It is even cautioned to avoid ice, as the ice may have been made with contaminated water.

Historically, low-doses of antibiotics[7] could be counted on to prevent the development of TD. However, increasing antibiotic resistance worldwide means that antibiotics are becoming less useful for this purpose and are contraindicated[8] for the purposes of preventing TD. When antibiotic prevention is needed, rifamixin is commonly used because it is a broad spectrum[9] agent that is poorly absorbed into the bloodstream, leading to a high concentration in the gut and a lower risk of side effects or interactions with other drugs. Aside from antibiotics, bismuth subsalicylate (often sold as Pepto-Bismol) is recommended for any traveler to aid in the prevention of TD. However, bismuth subsalicylate can have side effects[10], like darkening the color of the tongue and stool as well as constipation.

Probiotics and prebiotics have been discussed as alternatives to the above treatments, but their effects have been inconsistent. For example, in one placebo-controlled trial[11], taking Lactobacillus rhamnosus GG showed a modest TD risk reduction. However, a subsequent study using Lactobacillus found no effect[12].

The study under review aims to examine human trials involving the use of probiotics and prebiotics for the prevention of TD. It is an update to a previous systematic review[13] by the same author that was published in 2007.

Travelers' diarrhea (TD) is a common health problem experienced when traveling to countries with food safety standards and education that may not be as comprehensive as they are in developed countries. TD can be caused by a variety of microorganisms, but the most common cause appears to be E. coli. Probiotics and prebiotics have been studied as a potential preventive treatment for TD with mixed results. The study assessed here is a systematic review and meta-analysis of the randomized controlled trials (RCTs) published to date.

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