Probiotics

• Probiotics are live microbial food supplements that may have beneficial effects on intestinal microbial balance and associated impact on health. The two main species used in commercial preparations are lactobacillus acidophilus and bifidobacterium bifidum.
• Microbes have been used for many years in food preparation – for example, the manufacture of yoghurt and cultured dairy foods, kombucha and alcoholic fermentations. In recent years, a number of different probiotic formulations and supplements have been scrutinised in scientific research (primarily in infants) to examine their impact in modulating gut bacteria or microbiota. The gut microbiota performs several vital functions, including regulating mucosal immune activity, modulating host metabolic activity and protecting against intestinal infection. Dietary manipulation may enhance gut bacteria composition and metabolic activity and promote optimum immune function.
  • Dietary modification, and in particular increasing grain or fibre intake, should be recognised as the primary factor in enhancing gut microbiota diversity, and this can occur within a few days of dietary manipulation. Only after this has been optimised, should consideration be given to probiotic supplementation.
• Beneficial effects of enhancing the gut microbiota diversity may include improved intestinal tract health, enhanced immune system¹, greater bioavailability of nutrients, reduced lactose intolerance, lower prevalence of allergy in susceptible individuals, and improved mental health.²
• Apart from gut and respiratory health³, the purported benefits of enhancing gut microbiota diversity in a sporting context include improved body composition and lean body mass, reduction in stress hormones such as cortisol, attenuating age-related declines in testosterone levels, and increased concentration of neurotransmitters that might enhance cognition and mood^.4
• The mechanisms of action of probiotic supplementation are largely unknown, but may involve altering the makeup of gut microbiome, modifying gut pH (acidity), producing antimicrobial compounds, modulating gut permeability, stimulating immunomodulatory cells, preventing pathogen infection through ‘competitive exclusion’, or limiting the GI tract surface area available for colonisation.⁵
• Issues with dosage, viability of probiotic strains, lack of industry standardisation and potential safety issues, are being further investigated in the food additives industry and research studies. Applications of probiotics in sports nutrition and medicine are still emerging.⁶
• Although most studies in active individuals and athletes report positive effects on health, there is little evidence showing improvements in sporting performance. The general consensus is that probiotics may confer small variable benefits in performance and recovery, but further laboratory, clinical and field-based studies are required to provide definitive guidelines for athletes.

• Probiotics can be obtained from both foods and commercial supplements. Foods such as yoghurt and cultured milk products, and fermented drinks such as kombucha and kefir are a good choice given synergistic effects between food compounds and probiotic cultures. Supplements may be purchased in shell-stable (dried) format for easy use at home or when travelling, or as products that need to be refrigerated.
• Most studies report effective dosages of 10⁹-10¹⁰ organisms per day (i.e. – 1-50 billion bacteria). This concentration corresponds to about one litre of acidophilus milk (formulated at 2 x 10⁶ colony forming units/millilitre (cfu/ml). Some commercial preparations available in 2020 have up to 25 – 50 billion bacteria per dosage. Studies and clinical experience at the AIS have shown that most athletes will safely tolerate dosages of up to 35 – 50 billion in the commercial preparations that are currently available. Lower levels may benefit some individuals. Daily consumption is recommended as probiotics will pass through the intestine.
• The shelf-life of most probiotic products is about 3 – 6 weeks when kept at 4^oC. The shelf-life of dried supplements is about 12 months, but levels of probiotics may drop significantly over this time.⁷ The concentration of bacteria in food products varies substantially and some research indicates that commercially available products contain no live bacteria.

• Only after manipulation of diet to facilitate an increase in gut microbiota diversity, should probiotic supplementation be considered.
• Athletes with a prior history of gastrointestinal problems during periods of heavy training or around the time of competition might benefit from a course of probiotics.^8,9
• The AIS research on probiotics points to benefits in reducing the effects of respiratory illness.^10-15 Given the reasonable likelihood of athletes experiencing symptoms of gut and/or respiratory illness at some point in a training and competitive season a prophylactic approach before specific periods of training or major competition could be useful.
• Irrespective of whether the application is targeted or prophylactic an individual needs to commence daily supplementation approximately 14 days before domestic or international travel, competition or elevated training load, to allow for colonisation of bacteria in the gut.

May cause GI side-effects

• Some individuals report mild symptoms of stomach rumbles, increased flatulence or changes in the stool during the first week of supplementation as the gut microflora changes to accommodate the newly introduced species. These symptoms may be reduced by a gradual introduction of the probiotic protocol, building up to the recommended dose over a week or two.
• Individuals with a prior history of gastrointestinal tract problems such as coeliac disease or irritable bowel syndrome may be at greater risk of side effects such as an upset stomach or bowel problems.

Some products may not provide sufficient numbers or types of probiotics

• Several studies have reported low viability for commercially-available probiotic formulations and supplements with insufficient numbers of species, and in some cases the presence of species different to those declared on the label.
• Individuals are advised to obtain probiotics through a reputable source such as a sports dietitian or their sporting organisation/program. Priority should be given to evidence-based probiotics that have been tested independently under controlled conditions.

Evidence for benefits is still lacking certainty

Benefits may be highly specific to certain individuals and scenarios of use. Although most studies report positive health effects in athletes and active individuals, there is still no substantial scientific evidence to suggest that probiotics play an important role in improving an athlete's performance. Further research is needed before definitive protocols can be established to identify the likely health and performance benefits, supplementation protocols around training, travel and competition, and interaction with other targeted dietary practices.

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Supplement safety information www.sportintegrity.gov.au/what-we-do/anti-doping/supplements-sport, opens in a new tab

1. Clancy RL, Gleeson M, Cox A, Callister R, Dorrington M, D’Este C, et al. (2006). Reversal in fatigued athletes of a defect in interferon gamma secretion after administration of Lactobacillus acidophilus. Br J Sports Med, 40(4), 351-4.
2. Calero CDQ, Rincón EO, Marqueta PM. (2020). Probiotics, prebiotics and synbiotics: useful for athletes and active individuals? A systematic review. Benef Microbes, 11(2), 135-49.
3. Hao Q, Dong BR, Wu T. (2015). Probiotics for preventing acute upper respiratory tract infections. Cochrane Database Syst Rev, 2.
4. Jäger R, Mohr AE, Carpenter KC, Kerksick CM, Purpura M, Moussa A, et al. (2019). International Society of Sports Nutrition Position Stand: Probiotics. J Int Soc Sports Nutr, 16(1), 62.
5. Wosinska L, Cotter PD, O’Sullivan O, Guinane C. (2019). The Potential Impact of Probiotics on the Gut Microbiome of Athletes. Nutrients, 11(10).
6. Leite GSF, Resende Master Student AS, West NP, Lancha AH, Jr. (2019). Probiotics and sports: A new magic bullet? Nutrition, 60, 152-60.
7. Di Pierro F, Polzonetti V, Patrone V, Morelli L. (2019). Microbiological Assessment of the Quality of Some Commercial Products Marketed as Lactobacillus crispatus-Containing Probiotic Dietary Supplements. Microorganisms, 7(11).
8. Sivamaruthi BS, Kesika P, Chaiyasut C. (2019). Effect of Probiotics Supplementations on Health Status of Athletes. Int J Environ Res Public Health, 16(22). ASC36194
9. Walsh NP. (2019). Nutrition and Athlete Immune Health: New Perspectives on an Old Paradigm. Sports Med, 49(Suppl 2), 153-68.
10. Colbey C, Cox AJ, Pyne DB, Zhang P, Cripps AW, West NP. (2018). Upper Respiratory Symptoms, Gut Health and Mucosal Immunity in Athletes. Sports Med, 48(Suppl 1), 65-77.
11. Cox AJ, Pyne DB, Saunders PU, Fricker PA. (2010). Oral administration of the probiotic Lactobacillus fermentum VRI-003 and mucosal immunity in endurance athletes. Br J Sports Med, 44(4), 222-6.
12. Pyne DB, West NP, Cox AJ, Cripps AW. (2015). Probiotics supplementation for athletes - clinical and physiological effects. Eur J Sport Sci, 15(1), 63-72.
13. West NP, Horn PL, Pyne DB, Gebski VJ, Lahtinen SJ, Fricker PA, et al. (2014). Probiotic supplementation for respiratory and gastrointestinal illness symptoms in healthy physically active individuals. Clin Nutr, 33(4), 581-7.
14. West NP, Pyne DB, Cripps AW, Hopkins WG, Eskesen DC, Jairath A, et al. (2011). Lactobacillus fermentum (PCC®) supplementation and gastrointestinal and respiratory-tract illness symptoms: a randomised control trial in athletes. Nutr J, 10, 30.
15. West NP, Pyne DB, Peake JM, Cripps AW. (2009). Probiotics, immunity and exercise: a review. Exerc Immunol Rev, 15, 107-26.