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 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 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 of contaminated food or beverages. According to a publication 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 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 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 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 for the purposes of preventing TD. When antibiotic prevention is needed, rifamixin is commonly used because it is a broad spectrum 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, 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, taking Lactobacillus rhamnosus GG showed a modest TD risk reduction. However, a subsequent study using Lactobacillus found no effect.
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 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.
Other Articles in Issue #49 (November 2018)
Fasting: the fast-track to muscle loss?
The best way to restrict calories comes down to whatever works for each person. Some people prefer intermittent energy restriction (IER). New research suggests that it may come with at least one small downside, though.
Omega-3 PUFAs might help with anxiety, at least for some people
The first meta-analysis examining omega-3 PUFAs' effect on anxiety found a small, but significant, impact on anxiety overall.
Can collagen treat crow’s feet?
Animal and test tube research suggests that collagen supplementation could stimulate processes that can help skin keep looking young. Does this hold up in practice?
Interview: Sander Greenland MS, DrPH
Statistics and epidemiology luminary Sander Greenland discusses why nutrition research seems so contradictory, the pitfalls of magnitude-based inference, and more in this interview.
Can probiotics take the edge off anxiety?
Animal studies suggest that probiotics can have pretty significant anxiolytic effects. But clinical and animal studies don't always match up...
Does vitamin D actually help your bones?
This major meta-analysis takes a close look at whether vitamin D supplementation actually improves BMD and prevents fractures. The results are not too promising.
Mini: 12-month results from PREDIMED-Plus
How much does adding energy restriction and physical activity to a Mediterranean-style diet help with metabolic and cardiovascular disease risk? The PREDIMED-Plus study aims to find out.