May 17, 2015
Gut Check
Kelli Jennings

The healthy bacteria lingering in athletes’ intestines won’t make their stomachs turn. In fact, probiotics may be just what they need to reach new performance goals.

The following article appears in the May/June 2015 issue of Training & Conditioning.

It’s no secret that athletes work hard to be healthy. They train for hours each week and adhere to proper nutrition to turn their bodies into well-oiled machines. Yet, it’s often the little things that ultimately make the difference between success and failure in competition. Or in the case of probiotics, the microscopic things.

For some time now, scientists have acknowledged the benefits probiotics provide for the general population. As healthy bacteria that live in our guts, probiotics defend intestinal cells, improve digestive and immune system function, and influence nutrient absorption. Their presence in fermented foods and supplements makes them easy to access and consume.

Only recently, however, have athletes become aware of ways probiotics can improve performance. Along with the boost probiotics provide to immune function, there are benefits to consuming them before, during, and after training. Let’s dig in to learn more about each of these advantages, explore the best ways to incorporate probiotics into a meal plan, and discover how some tiny organisms can help athletes.


While many traits of elite athletes are associated with reduced illness risk, such as cardiovascular fitness and lean body mass, the preparation required to stay at a high level can have an impact on overall health. Long training hours–especially for an athlete who has not dialed in their nutrition plan, developed a smart workout schedule, or built in adequate recovery periods–can set the body up for nutrient deficiencies, over-training, and chronic fatigue. When viruses and infection-causing bacteria are introduced to the mix, athletes can be predisposed to sickness and stay that way for weeks or months.

However, probiotics can change this. Consuming fermented foods and/or probiotic supplements daily can vastly improve an athlete’s gut flora, and gut health correlates to whole-body health.

For instance, a 2014 study published in Critical Reviews in Food Science and Nutrition found that regular probiotic consumption not only led to better digestion and fewer gastrointestinal issues, but also improved immune function, recovery, and overall health. In athletes, this can translate to less time missed due to illness and increased recovery from training.

The gut is also the gateway through which nutrients systemically affect the body. When the gut is healthy, foods are digested correctly, and nutrients are either broken down and absorbed or eliminated if needed.

But when the gut is compromised, harmful nutrients like whole proteins can invade the bloodstream. A 2013 study from Current Nutrition and Food Science found this could cause inflammation, immune-function reactions, or food intolerances, all of which could drastically impact performance for athletes.

Beyond boosting gut health, probiotics directly support immune function by promoting higher levels of interferon, a protein made and released by cells in response to the presence of viruses, bacteria, and parasites. The production of interferons can be suppressed in some athletes during periods of intense, extensive training, and past studies in the British Journal of Sports Medicine and Critical Reviews in Food Science and Nutrition showed that daily supplementation of probiotics by fatigued athletes led to increased interferon production. Over time, these individuals also showed decreased incidence of illnesses like colds and mononucleosis.

These findings are further supported by a 2008 study published in British Journal of Sports Medicine. It revealed that endurance athletes who took a lactobacillus fermentum probiotic supplement experienced half the number of days coughing and sneezing due to colds and other viral infections over a four-month period than those in a control group. Athletes taking probiotics also exhibited higher levels of gamma interferon.


Before hitting the track, field, or court, athletes often consume pre-training fuel to give their bodies sufficient energy and nutrient sources during their workout. However, I’ve worked with a number of athletes who experience acute stomach distress and reflux when they eat right before practice.

Probiotics can be a great solution to soothe gastrointestinal discomfort. When probiotics are present in the gut, acute nausea and reflux are reduced while food transit time is increased, allowing foods and nutrients to more efficiently leave the stomach and become useful to the body.

With my clients, I often recommend drinking a probiotic smoothie before any workout exceeding two hours. Here are the ingredients for one of my favorite options:

• 1 small banana

• 1 cup frozen or fresh berries

• 1 tablespoon chia seeds

• 1/2 cup to 1 cup of plain Greek yogurt

• 1 to 2 tablespoons of organic honey

• 1/2 tablespoon of organic coconut oil

• Water or ice for desired consistency.

This smoothie delivers many nutrients that can sustain an athlete during a training session. For starters, yogurt offers quick probiotics and long-lasting protein, and the coconut oil provides special fatty acids called medium-chain triglycerides, which act as an energy source in cells. The fruit, chia seeds, and honey deliver needed long-lasting carbohydrates for energy, natural enzymes to improve digestion, fiber (prebiotics) that acts as a food source for probiotics, and antioxidants to keep cells healthy and repair damage brought on by the extra oxygen reactions during training. Many athletes I’ve worked with have found the smoothie is a great energy source that doesn’t cause the stomach distress or fullness of many pre-workout meals.

Athletes should also consume fuel during workouts that last more than 90 minutes. Since probiotics enhance nutrient absorption, they can help athletes during long-duration training by allowing the gut to deliver more nutrients to the bloodstream. Specifically, the absorption of carbohydrates, electrolytes, fluids, and amino acids can minimize muscle damage and lower an athlete’s risk of dehydration and cramping.

When workouts exceed 90 minutes, I recommend athletes take a probiotic supplement pill every two to three hours. For those who suffer from digestion issues, I suggest increasing that intake to every hour.

In addition to assisting with nutrient absorption, some research indicates that consuming probiotics during training may lead to more direct performance enhancement. At the International Probiotic Association’s World Congress in 2012, one brand presented a study that found probiotics improved athletes’ VO2 max and anaerobic threshold. Although more third-party research is needed and the exact trigger for this is not yet known, one theory suggests that better nutrient uptake from probiotic consumption means more energy per hour of training.

Finally, all athletes know how important recovery is following a strenuous workout, but few are aware of the ways probiotics can help with this. One important element in recovery is eliminating free radicals, which are abundant after training and can damage cells and tissues. Antioxidants found in foods can neutralize free radicals. Since taking probiotics after exercise can increase the absorption of antioxidants, it helps with the removal of free radicals and keeps athletes from experiencing their negative effects.

A 2011 study in Current Microbiology evaluated the effects of probiotics lactobacillus rhamnosus and lactobacillus paracasei on oxidative stress (from free radicals) in athletes following intense physical activity. Over a four-week period, 12 participants consumed these two probiotic strains each day and 12 did not. Although the results indicated high levels of oxidative stress in all participants after exercise, those who consumed the probiotics also exhibited increased plasma antioxidant levels. The researchers concluded that the two probiotic strains contributed to the strong antioxidant activity.

Besides providing optimal pre-training fuel, a delicious smoothie with yogurt or added probiotics, protein, and fresh fruits and vegetables is a powerhouse post-workout snack. To further gear it toward recovery, athletes can simply add a scoop of their favorite protein powder.


If athletes would like to tap into the power of probiotics, there are lots of ways to incorporate the healthy bacteria into their diets. I recommend making probiotics a daily nutrition go-to through fermented foods and freeze-dried supplements.

It’s important to understand that there isn’t a “magic bullet” amount or perfect dose of probiotics. Our floras change with age, antibiotic use, medical issues, gut conditions, and more. Some people simply have healthier guts and more bacterial colonies than others and may not need to consume as many probiotics. Others, specifically those who have battled chronic colds and infections, digestive issues, food intolerances, and environmental allergies, will likely benefit from more frequent doses.

In addition, multiple strains of probiotics have been identified in the human gut flora, and different individuals will benefit from different strains. Therefore, it’s important to experiment with consuming a variety of strains through many types of products. Here are some easy, effective ways for athletes to add probiotics into their diet:

Eat naturally fermented foods and drinks each day. A convenient way to ensure dairy-tolerant athletes have access to healthy bacteria on a daily basis is to include yogurt in their dietary plan. Ambitious athletes can even make their own high-probiotic yogurt at home. Other fermented food options include kefir, kombucha, miso soup, sauerkraut, and several types of microalgae, such as spiruline, chorella, and blue-green algae.

Try fortified foods with added probiotics. Several companies now add probiotics to foods that don’t naturally contain them. You can find dark chocolate products, instant oatmeal, cereals, juices, meal replacement shakes and powders, non-dairy milks, and much more with added probiotics. These are great if athletes tire of fermented dairy or can’t tolerate it but still want a tasty probiotic option. In fact, many of these foods also contain inulin, a prebiotic fiber that serves as probiotic food. (Yes, healthy bacteria need to eat, too. See “Feeding the Flora” below for more on prebiotics.)

Add a daily, high-quality, multi-strain probiotic supplement. This can be especially beneficial during the winter when viruses are most active. Have athletes look for supplements that are freeze-dried and do not require refrigeration for the most viable bacteria. In addition, they should try supplements that contain eight or more strains of bacteria for optimum probiotic diversity.

In my sports nutrition practice, my clients have seen better recovery, improved health, and better athletic performance with probiotics. No matter what sport athletes are training for, there’s really no downside to probiotics and very little risk in adding them to a nutrition regimen. I recommend probiotics as an easy, delicious, and inexpensive way to make a big impact on wellness and athletic performance.


Since probiotics are alive and kicking in our guts, they need a food source to continue to proliferate. Prebiotics are specific fibers on which probiotics feed, and can make a world of difference on an athlete’s health.

The most effective and researched prebiotics are inulin-type fructans. These include inulin, oligofructose, and fructooligosaccharides (FOS, a synthetic prebiotic often added to supplements and fortified foods). In nature, they are found in over 36,000 plant species. Humans often consume them from bananas, chicory root, onions, leeks, sweet potatoes, beans, and legumes, and they are found in smaller amounts in most other fruits and vegetables.

Prebiotics are often added to supplements. For example, FOS is derived from chicory root and serves as a synergistic additive to probiotic supplements. I consider these prebiotics as good fertilizer to get things growing, but athletes must also continue to nurture their probiotics with a healthy diet full of prebiotic-containing plants.

Kelli Jennings, RD, is the founder of Apex Nutrition, LLC, an online sports nutrition planning and coaching service based in Golden, Colo. She's also the sports nutritionist for Team Prep USA Running and several professional and amateur mountain bike teams. Jennings can be reached through her website at:

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