Jäger R, Mohr AE, Carpenter KC, Kerksick CM, Purpura M, Moussa A, Townsend JR, Lamprecht M, West NP, Black K, Gleeson M, Pyne DB, Wells SD, Arent SM, Smith-Ryan AE, Kreider RB, Campbell BI, Bannock L, Scheiman J, Wissent CJ, Pane M, Kalman DS, Pugh JN, Ter Haar JA, Antonio J.,  International Society of Sports Nutrition Position Stand: Probiotics. Journal of the International Society of Sports Nutrition. Dec 21;16(1):62. 2019.

‘Probiotics’ has become a trendy word that you see added to all sorts of foods and marketed to all types of people for a wide variety of reasons. With all the information out there I wanted to give a summary from the latest position stand of what the latest research on probiotics in athletes has shown and what the recommendations are. Spoiler alert, we still need a lot more research in this area.

To know why probiotics may be important for humans, we first need to know what our microbiome is, and Harvard Public Health does a good job breaking Ursell’s research down:

Picture a bustling city on a weekday morning, the sidewalks flooded with people rushing to get to work or to appointments. Now imagine this at a microscopic level and you have an idea of what the microbiome looks like inside our bodies, consisting of trillions of microorganisms (also called microbiota or microbes) of thousands of different species. These include not only bacteria but fungi, parasites, and viruses. In a healthy person, these “bugs” coexist peacefully, with the largest numbers found in the small and large intestines but also throughout the body. The microbiome is even labeled a supporting organ because it plays so many key roles in promoting the smooth daily operations of the human body.

Each person has an entirely unique network of microbiota that is originally determined by one’s DNA. A person is first exposed to microorganisms as an infant, during delivery in the birth canal and through the mother’s breast milk. Exactly which microorganisms the infant is exposed to depends solely on the species found in the mother. Later on, environmental exposures and diet can change one’s microbiome to be either beneficial to health or place one at greater risk for disease.

The microbiome consists of microbes that are both helpful and potentially harmful. Most are symbiotic (where both the human body and microbiota benefit) and some, in smaller numbers, are pathogenic (promoting disease). In a healthy body, pathogenic and symbiotic microbiota coexist without problems. But if there is a disturbance in that balance—brought on by infectious illnesses, certain diets, or the prolonged use of antibiotics or other bacteria-destroying medications—dysbiosis occurs, stopping these normal interactions. As a result, the body may become more susceptible to disease.

What are probiotics and where are they found:

Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (host meaning your gut microbes)

To break it apart literally it means:

Pro – for

Biotic – life

They are described by: genus, species, and strain

            Ie. Lactobacillus acidophilus SPP (commonly found in yogurt)

Reported in CFUs on labels – colony forming units

Ie. 10 million CFUs

They are found naturally in fermented foods like: yogurt, kombucha, kefir, sauerkraut, miso, and some pickled vegetables. (Sorry, yes beer is fermented but the live microorganisms are killed in the beer making process – always look for labels that say ‘live and active cultures)

They were first research for their reported health benefits on the supporting/improving of the immune system, maintenance of the intestinal barrier, fight against pathogen adhesion to host tissue, and production of different metabolites such as vitamin, minerals, short chain fatty acids, and molecules that act as modulators in the gut-brain axis communication.

The body of research is growing in athletes and probiotics:

• Studies are now looking at the effect on: gut health, exercise performance, recovery, physical fatigue, immunity, and even body composition (based on positive rat studies)

On the flip side things that improve your microbiome outside of probiotics:

• Exercise has a positive relationship on gut biodiversity (your microbiome)
• Protein has a strong positive impact on the microbiota
• Carbohydrates are well known for their profound effect on the gut microbiota with fiber (coming from whole grains and fruits/vegetables) associated with microbial richness and diversity

Benefits of Probiotic supplementation that are being researched:

One thing we know of athletes with high training volume – Strenuous and prolonged exercise places stress on the gastrointestinal (GI) tract and increases the likelihood of multiple symptoms associated with a disturbance of gut microbiota (ie. Diarrhea, bloating, cramps, etc.) and decreased performance.

The GI tract is also heavily protected by the immune system as it is a major gateway for pathogens, therefore much research has been done on probiotics defense against upper respiratory tract infections (URTI).

Probiotics may also regulate mucosal immune response, improve macrophages (pathogen fighters), and modulate expression of genes associated with macrophage activity.

Although this all seems promising it is important to remember: research is quite new in athletes

• Of the 24 studies – 17 reported null effects and 7 reported significant improvements
• With multi-strain probiotics seeming to have more positive effects than single strain

Within those studies some of the positive results are below:

• Lactobacillus planetarium has been shown to activate cell growth signaling pathways in gut enterocytes which in turn increases protein metabolism in the gut as well as maintain gut permeability (essentially they control of what passes through the gut wall)
• Bacillus coagulans GBI-30, 6086 enhances the health of the cells of the gut lining through improved nutrient absorption including minerals, peptides, and amino acids by decreasing inflammation and encouraging optimum development of the absorptive area of the gut villi. They have been shown to increase protein absorption (Kimmel et al. 2010) (Maathuis et al., 2010) when added to a protein post-workout drink.

• B. subtilis – no performance improvement, but lower serum TNF-alpha concentrations (which is your immune system regulator – concentrations are typically higher in the case of infection/illness).
• Although a few studies have found multi-strain probiotics increase VO2 max, aerobic power, training load, and time to exhaustion, more studies have found no such effect.
• The effect of probiotics on body composition is mixed, and many of the studies are poor study design, as of now the research is lacking.

Let’s talk about the Immune System:

The mucosal lining of the GI tract is the first-line-of-defense against invading pathogens and is an important border with the host immune system with approximately 70% of the immune system in the gut.

Exhaustive exercise is known to negatively impact immunity.

Therefore, many studies have focused on this effect of probiotics and immuity:

• Of the studies on athletes and immune system (22), 14 showed significant improvement and 8 showed no effect.
• B. animalis ssp. Lactis Bi-07 in active people showed 27% reduction in URTI episode and 0.8 month delay in time to illness
• However, most studies are conducted on endurance athletes
• Note: The body of evidence favors probiotics in reducing URTI, however there is large differences in stains used, duration, population, and effects measured.

The beneficial effect from probiotics on incidence of URTI is possibly linked to enhanced systemic and mucosal immunity.

In summary for the immune system, probiotic supplementation may be viable to support immune function during intense training.

Let’s talk about GI tract health

Exercise induced redistribution of blood can result in splanchnic hypoperfusion (meaning blood is diverted from the abdominal region and your gut) as a possible mechanism for gut dysfunction or the up and down movement of running can increase the frequency of gut symptoms.

Disruptions in the GI system can impair the delivery of nutrients and may affect performance.

Of the 10 studies, 6 reported no effects – 4 reported positive effects

• In the positive results, zonulin and endotoxin concentrations were reduced (markers of gut permeability).
• Several lactobacillus species have been noted to increase mucin expression in human intestinal cell lines and thus may help restore mucus layer.
• Adhesion of probiotics to the intestinal mucosa have shown to favorably modulate the immune system and the fighting of pathogens by preventing pathogen binding and creating a hostile environment that may inhibit the colonization of pathogenic bacteria.

Probiotic Safety:

They have been used safely in foods and dairy products for over 100 years in adults and infant formula (unknown in vulnerable population)

It is important if you are looking to take supplements that you take a reputable brand (and NSF certified if possible). Many probiotics, when tested, didn’t have the stated amount or strains in them.

Most Studied:

• Bifidobacterium (ssp. Adolescentis, animalis, bifidum, breve, longum
• Lactobacillus (ssp. Acidophilus, casei, fermentum, gasseri, johnsonii, reuteri, paracasei, plantarum, rhamnosus, and salivarius

International Olympic Committee recognizes benefits of probiotic supplementation with a daily dose of 1 x 10 billion taken for 14 days prior to competition or event.

Duration of effect: After 8 days of ceasing probiotic intake levels reduce back to non-detectable in the gut so they only are effective if you are taking them

Timing or consumption: 30 minutes before a meal or with a meal – improves bacterial survival rate (also better taken with milk or oatmilk)

Probiotic supplementation is more likely to alter the microbiome composition of dysregulated microbiomes compared to healthy ones, like in the case of diarrhea or antibiotic use.

Summary:

Research in athletes shows promising benefits for immune and gut health.

Here is a quick guide to which probiotic may be beneficial and when:

Probiotic	Effect	Food/Supplement
L. acidophilus	Treat travelers and antibiotic related	Certain brands of yogurt and milk, miso and tempeh and supplements
L. helveticus and B. longum	Immune and psychological health	Kefir, Yogurt, fermented cheeses and supplements
L. plantarum	Psychological health, increased immunity and improved metabolic conditions, preliminary research on endurance performance	Kimchi, fermented beets, pickles cucumbers, and sauerkraut, and supplements
L. reuteri	Reduce inflammation and allergies	Fermented vegetables, dairy products and supplements
L. rhamnosus GG, or LGG,	Most effective probiotic in treating infectious diarrhea	Kefir, Kombucha, yogurt, and supplements
B bifidum	Hopeful treatment for certain GI conditions, such as constipation, traveler’s diarrhea, IBS, ulcerative colitis and H. pylori	Kefir, yogurt, buttermilk, miso, tempeh, pickles, kimchi, cured meats, sauerkraut and sourdough, and supplements
S. boulardii (yeast)	Used for years to treat several gastrointestinal conditions, including travelers’ diarrhea and C. diff	Supplement
B coagulans	Beneficial effects on protein and other nutrient absorption	Supplement
L rhamnosus B bifidum, B lactis, E faecium, L acidophilus, L brevis, and L lactis L salivarius	Linked to improved gut health in athletes	Supplements and yogurts
L fermentum L casei L delbrueckii bulgaricus, B bifidum, and S salivarus thermophilus (in yogurt drink) B animalis lactis L gasseri, B bifidum, and B longum B bifidum, B lactis, E faecium, L acidophilus, L brevis, L lactis L helveticus Lafti	Have been shown to improve immune health in athletes	Supplements and yogurts
B. animalis ssp. Lactis Bi-07	Reduce URTI by 27%	Dairy products and Supplements

Resources:

The Nutrition Source, Harvard Public Health. Microbiome. https://www.hsph.harvard.edu/nutritionsource/microbiome/

Kimmel M, Keller D, Farmer S, Warrino DE. A controlled clinical trial to evaluate the effect of GanedenBC(30) on immunological markers. Methods Find Exp Clin Pharmacol. 2010 Mar;32(2):129-32. doi: 10.1358/mf.2010.32.2.1423881.

Maathuis AJ, Keller D, Farmer S. Survival and metabolic activity of the GanedenBC30 strain of Bacillus coagulans in a dynamic in vitro model of the stomach and small intestine. Benef Microbes. 2010 Mar;1(1):31-6. doi: 10.3920/BM2009.0009.

Ursell, L.K., et al. Defining the Human Microbiome. Nutr Rev. 2012 Aug; 70(Suppl 1): S38–S44.