Book Review Microbiota &?Sport

In athletics, competitors are all at the top of their game and seeking the 1% difference that will snatch them the victory. With the emergence of microbiome science, and increasing understanding of the interplay between diet, microbes, and an individual’s health and performance, it makes sense for the new generation of athletes and nutritionists to take into account this opportunity to do even better, based on curated symbiosis.

The microbiome has also been referred to as the “adaptome”: “the microbial genome can be considered as the variable part of the human genome, the one that allows our organism to adapt to external stimuli”. It is the part of our genes that we can change to better accompany us toward our goals.

Roberta Martinoli and Silvia Barbaresi have extensively studied human nutrition, and Silvia is a doctor in sports nutrition. Together, they have proposed a small book to shed light on this new knowledge and learn to leverage this adaptome:?Microbiota & Sport. I thank them for sending me a copy graciously.

Today, it is only available in Italian, but here are some take-home messages.

The exercise conundrum

Although exercise has been shown to enhance the microbiota setting and its diversity (as previously highlighted by Tim Spector in?The Diet Myth, and many articles such as?this one), this appears to be true of medium-intensity exercise. The intensity exerted or pursued by athletes is of a different level. The authors explain that the relationship between exercise and microbiota balance follows a J-shaped curve: medium-intensity exercise is best, no exercise is worse, but intense training and straining is deleterious too, leading to digestive issues and lesser immune defenses.

So how can microbiome interventions help athletes? There are 4 main domains in which they can help: digestive health, immunity, performance, and mental.

1.?Digestion

Athletes’ diet is usually poor in complex carbohydrates, which hardly fosters a healthy microbial setup and ecology. Without sufficient fiber and the right bugs to digest them into short-chain fatty acids, it is impossible to generate the compounds that feed the enterocytes and ensure the integrity of the gut lining (butyrate generates in itself 70% of the energy needed by colonocytes, and it participates to satiety and metabolism at several levels).

However, having more vegetables would imply the risk of going into a race without a well-emptied gastrointestinal tract.

Athletes have a high intake of protein, but in parallel should minimize their intake of toxic amines.

It’s not only the diet, but the energy diverted to the muscles during effort deprives the digestive system of blood flow, which encourages intestinal inflammation and starts a vicious cycle of permeability, inflammation, and reduced absorption.

In endurance sports, 50% of athletes manifest gastrointestinal tract (GIT) issues that compromise their race or post-race recovery. Iconic Bill Rodgers, 22-times marathon winner, claims “Marathons are won or lost more in the toilets than at the table.”

“Marathons are won or lost more in the toilets than at the table.” — Bill Rodgers, marathoner.

In athletes, endotoxemia bears another name: “gastrointestinal syndrome induced by intense physical exercise”. This syndrome is marked by a leaky gut and an associated increase in i-FABP (intestinal fatty acid binding protein), which goes together with a malfunction of the protein responsible for transcellular transportation, and absorption deficits.

Probiotic strains have been studied in the improvement of gastrointestinal symptoms and indicators of gut permeability and inflammation in athletes. The authors report their review of the literature in a 5-page-long table. As summary, they point to some strains as leading the sports GIT support pack:

• L. rhamnosus?GG at 40 billion cfu/day (Kekkonen?et al.?2007?on 141 marathon runners for 3 months, reducing GIT symptoms in the probiotic group during training by 33%, NS, and after the race by 57%, p=0,046)
• a blend of?B. bifidum?W23,?B. lactis?W51,?E. faecium?W54,?L. acidophilus?W22.?L. brevis?W63 and?L. lactis?W58, 10 billion cfu/day (Lamprecht et al., 2012, with 23 mixt endurance athletes for 14 weeks, showing a significant reduction of zonulin.

2.?Immunity

On average, an adult gets upper respiratory tract infections 2 to 4 times a year. But athletes are more prone to this kind of infection. And they are of more consequence to them: they steal them from, at best, days of training, and at worst, opportunities to compete.

Because of the common leaky gut situation, they are more exposed to pathogen translocation, and chronic inflammation. In this situation, a simple signal can lead to a cytokine storm, an overreaction of the immune system that can no longer count on the regulators meant to tune down the signal.

In addition, the exercise is followed by a window of 3 to 72 hours of immune depression (more often, about 24 hours). Athletes training every day can easily be vulnerable virtually all the time.

Probiotic strains have been shown to reduce the risk of infective diseases in athletes and a thorough literature review is provided by the authors in form of a 6-page-long table. A sum-up highlights the potential of the following strains:

• L. casei?Shirota 6.5 billion cfu twice a day (Gleeson et al., 2011?: 16 weeks in 42 trained volunteers shows a significant reduction of upper respiratory tract infections (URTI) by 36% in the probiotic group)
• B. animalis?subsp.?lactis?BI-04 20 billion cfu/day (West et al., 2014?show that for in 465 active men and women, 23 weeks with this strain reduced upper respiratory illness episodes with a hazard ration of 0.73, p=0,022).
• a blend of?B. bifidum?W23,?B. lactis?W51,?E. faecium?W54,?L. acidophilus?W22.?L. brevis?W63 and?L. lactis?W58, 10 billion cfu/day (Strasser?et al., 2016?show in 29 trained participants supplemented for 12 weeks that the probiotic reduces by more than half the URTI symptoms (p=0,02))
• L. helveticus?lafti L10 20 billion cfu (Michalickova?et al., 2016?in 39 elite athletes for 14 weeks show a reduction of duration of URTI (7.25 ± 2.90 vs. 10.64 ± 4.67 days, p = 0.047) and decreased the number of symptoms in the probiotic group (4.92 ± 1.96 vs. 6.91 ± 1.22, p = 0.035).

3.?Performance

For the time being the Olympic Committee has recognized only a few active substances with the capacity to improve sports performance — caffeine, creatine, nitrate, sodium bicarbonate, and beta-alanine sodium. But for probiotics too, scientific evidence points to a lot of potential to act through different ways — reduction of gut permeability, inflammation, oxidative stress, but also improving the access to energetic resources in the body, through the improvement of the nutritional status and the muscle recovery, etc.

For example, Veillonella is thought to improve lactate clearance thanks to its metabolism transforming lactate into propionate (Scheiman et al., 2019).

There is more data in endurance sports compared to strength sports, and again, a 5-page table summarizes the evidence backing effective strains. Certain strains were shown to improve VO2 max, or resistance to tiredness, muscle recovery, muscle mass, endurance, and/or distance ran.

According to both authors, strains leading the pack for the improvement of performance include:

• B. coagulans?BC30 at 1 billion cfu/day in combination with casein (Jager?et al., 2016, the 3 weeks intervention with 29 athletes showed an improvement on the muscle recovery at 24 and 72h (p<0,0001) and reduced soreness after 72 h)
• B. breve?BR03 in association with?S. thermophilus?FP4 with 5 billion cfu/day each also improved muscle recovery (Jager et al., 2016?with 15 trained men for 2 weeks shows that probiotic supplementation likely enhanced isometric average peak torque production at 24 to 72 h into the recovery period following exercise)
• L. plantarum?TWK10 100 billion cfu/day for resistance (Huang?et al., 2018?with 16 amatorial athletes supplemented for 6 weeks showed an impressive +50% in time to exhaustion (817+-79 seconds in the placebo group vs 1292 +-204 in the probiotics group, p=0,04)

4.?Mental

Although the authors don’t dedicate a full chapter to the gut-brain axis and its potential to improve athletes’ well-being and mental preparation, they highlight that some sports professionals, including football players, see a high prevalence of depression and anxiety. Given the role that the gut plays in regulating emotions, through neurotransmitters and their precursors, endocrine and immune signals, and direct vagus nerve communication, there are grounds to modulate the microbiome to relieve athletes from stress and anxiety, help them focus and have positive projections. For instance,?L. casei?Shirota at 30 billion cfu/day “favorably improved brain waves, favoring relaxation and attention, improving the quality of training, brain function, concentration, and supporting a positive physiological approach towards exercise, needed to contrast tiredness” (Adikari?et al., 2020).

I’d like to point that a lot of publications reported the composition of their probiotics only down to the species level, or failed to report the dosage implemented, making any recommendation impractical, and thus did not make it to the present summary.

Guide for the selection of probiotics in 10?criteria

The authors report of experts who came up with 10 recommendations for the prescription of a probiotic — I haven’t found the reference to this list. (Although the book is extensively researched and lists its references, the publications are numbered in the text, but in alphabetical order in the reference list, unfortunately).

You can find the 10 recommendations in the following table, although I would be keen to contest several of these requirements.

What do you make of these considerations?

From where I stand, there is confusion between the concept of colonization and the concept of efficacy. The probiotics definition shows that vitality is important, and benefit is important. But mediating the effect through colonization is not part of the definition, and rightfully not. Probiotics are not thought to colonize the human gut in the long term: they mostly exert their effects through transient contact with the mucus, dendritic cells, other bacteria, and the rich interplay of molecular, endocrine, immune, and nervous signals. These effects do not require a long-term establishment. In a context in which the mucus and its inhabitants are fully renewed roughly every three days in humans, engraftment is a challenge for any new bug, but it’s reasonable to ask the bacterium to play the role that’s asked of it. This?article?from the International Scientific Association for Probiotics and Prebiotics expresses it better than I could.

Probiotics should be safe, but the absence of antibiotic genes overall is an overstatement. There is one great strain out there that prescribers should certainly consider using in their medical practice, called?B. longumW11, which is resistant to rifaximin. It can thus be?used concomitantly with the antibiotic?and remains safe because the antibiotic resistance gene is located on the bacterial chromosome (not on a plasmid) and can’t be transferred to other bacteria.

Also, the question of single strains vs multiple strains is for me not a key question — once we select probiotics based on the clinical evidence, we should simply use the formulation, single strain or multiple strain which it may be, and dosage, that was studied.

Conclusions

Athletes and the nutrition professionals that accompany them will have more work to figure out personalized, smart diets that take into account the athlete not as an isolated individual, but in its holobiont complexity.

The dysbiosis that characterizes professional athletes also raises question marks around the initiatives towards reproducing athletes’ microbiota. However, lead researcher in the sports nutrition field?Chad Kerksick?thinks it is more the mechanical and physiological diversion of blood from the GIT that leads to GIT symptoms rather than dysbiosis. It would be interesting to dig deeper into the healthfulness or non-healthfulness of elite athletes’ microbial makeup.

Fecal Microbial Transplant has been proposed but safety considerations should be well evaluated prior to transferring markers of leaky gut and inflammation. “Primum non nocere”.

In the end, as the authors commend, and so does the International Society of Sports Nutrition, probiotics have a role to play in improving athletes’ quality of life and performance. Certain probiotic strains are proposed for specific purposes: the precision probiotic?Hafnia alvei?HA4597?has even been dedicated a short chapter and is suggested to help athletes who compete by categories of weight. They often struggle to meet the weighing day target and could benefit from the strain’s propriety to enhance the feeling of fullness even when on a diet.

The authors thus recommend the use of probiotics by athletes, with a few rules of thumb:

• to guarantee safety, dosage, and conservation. Athletes are vulnerable, and even though to date no adverse events were reported for this population, it is crucial to guarantee the safety of the formulation.
• protocols of supplementation should last at least 14 days, and the authors suggest administration for 4 weeks pre-season
• in the future, prescription could be better personalized ad hoc for the specific needs and objectives of each athlete.

Now get to it… unless you prefer to think that it’s?your gut microbes that demolish your exercising motivation?