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DEPARTMENTS: Fitness Focus

Potential Benefits of Probiotics in Highly Active People: Brought to you by the American College of Sports Medicine

Roy, Brad A. Ph.D., FACSM, FACHE; Troy, Lynn N.D.

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ACSM’s Health & Fitness Journal: November/December 2013 - Volume 17 - Issue 6 - p 3-4
doi: 10.1249/FIT.0b013e3182a9429d
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Preventing injury and illness is a priority for both recreational and competitive athletes. Training smart by gradually increasing volume and intensity, allowing recovery between workouts, getting adequate sleep, and consuming a well-balanced diet should be critical components for everyone’s exercise training plan.

Historically, athletes have had a keen interest in nutritional intake, looking for that slight edge that might enhance their competitive performance. In addition to focusing on dietary intake, many physically active people take dietary supplements, hoping to compensate for potentially poor food choices. Although not a substitute for poor diet, at times, dietary supplements may be helpful for the athlete.

The fact that immunity and host resistance to illness are influenced by a person’s nutritional intake has created a growing interest in the use of probiotics. During the past decade, probiotics have become increasingly popular among athletes desiring to reduce gastrointestinal (GI) disturbance and their susceptibility to upper respiratory tract infections during periods of heavy training and competition. Symptoms such as gut pain, cramping, diarrhea, bleeding, and nausea have been documented in some highly active people, especially those participating in prolonged endurance events.


Found in supplements and fermented food sources such as kefir and yogurt, probiotics are beneficial bacteria that inhabit the mucus lining of the intestine. These live microorganisms transiently alter our intestinal microbial flora, the diverse bacterial population that inhabits the GI tract, by interacting with various receptors on intestinal cells and the common mucosal immune system. The mucosal lining of the gut serves as the first line of defense against invading pathogens.

The primary interest in probiotics for athletic people is their potential ability to decrease the incidence of upper respiratory tract infections, improve gut permeability, and lessen the inflammation that occurs with endurance sports. Although probiotics are unlikely to result in direct benefits on physical performance, there are a number of small studies that have produced modest evidence that probiotics can provide benefits that indirectly improve performance in highly active people. Probiotics seem to reduce mild to moderate symptoms such as stomach pain or cramps, bloating, nausea, and unexpected changes in stool composition and frequency. Data also suggest that highly active people taking probiotics are less likely to experience upper respiratory tract infections that might interrupt their training schedules. Although current studies show promise, additional research is required to provide definitive answers. One of the limitations of the current research is the use of a large variety of types of probiotics, called strains. Some studies use multiple strains whereas others focus on one particular strain, and this variability makes it challenging to compare the significance of the results across studies.


Merely taking a supplement does not fully compensate for an inadequate diet and, in some cases, may be a poor investment because of inaccurate labeling (not getting what’s stated), creative marketing (false claims and hype), contamination issues, and excessive/unnecessary consumption (more is not necessarily better). Although generally safe, the quality of supplements is quite variable. Poor-quality probiotics may not contain viable bacteria and, in some cases, have even been found to contain harmful organisms. Thus, people with compromised immune systems, especially those with low white blood cell counts, should not take probiotics. Some people also may experience side effects, such as an increase in gas.


Emerging evidence suggests that probiotic supplementation may assist highly active people participating in recreational and athletic events by reducing the risk of respiratory and GI challenges during periods of intense and stressful physical activity. Although existing data are promising, additional studies are necessary before definitive recommendations can be made. Thus, it is prudent for athletes of all ages to seek advice from a sports nutrition expert, such as a certified sports dietician, before reaching for the supplement jar.

© 2013 American College of Sports Medicine.