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LcS Research | SPORTS

Sports people engaged in heavy training programmes and competition, particularly for endurance events, can show an increased susceptibility to common infections. For instance, upper respiratory tract infections are more common in endurance athletes. Elite athletes and sports people have an increased risk of infection due to their increased exposure to pathogens and the effects on their immune system of their lifestyle and activity e.g. physiological, psychological and/or environmental stress, poor diet and/or sleep).

Several studies in athletes indicate that low levels of salivary IgA (an indicator of mucosal immune status) may be one of the underlying reasons for this (Neville et al 2008; Niemann et al 2002).

  • Exercise and immune function. Gleeson M & Thomas LV. Complete Nutrition (2008). This free article can be ordered by contacting

Research in this field has been conducted with Lactobacillus casei Shirota, investigating reduction of colds and gastrointestinal discomfort, and reduction of ammonia levels generated during exercise. Reprints of the studies below can be ordered by contacting us.

Gleeson M et al (2011)

Daily probiotic’s (Lactobacillus casei Shirota) reduction of infection incidence in athletes. Int J Sport Nutr Exercise Metab 21:55-64

View the Study

A key double-blind, placebo-controlled study in elite sports people was conducted by Professor Mike Gleeson at Loughborough University, randomising 84 healthy adults engaged in regular sports training (mainly running, cycling, swimming, triathlons, team games and racquet sports) to take a probiotic (L. casei Shirota; LcS) or placebo for 16 weeks. At baseline, 8 and 16 weeks, resting blood and saliva samples were taken and tested for a broad range of immune parameters: immunoglobulins, cell counts and cytokines. The subjects also kept weekly records of their training and any illness. Subjects were required to maintain a minimum level of training.


Analysis of the subjects who completed the full 16 weeks of the study (n = 58), showed that consumption of this probiotic strain was associated with:

  • Significantly lower levels of upper respiratory tract disorders (50% lower in the probiotic group compared to placebo; P less than 0.01)
  • restoration of levels of salivary IgA
  • significantly fewer days with GI discomfort symptoms (P=0.008)
  • significantly lower proportion of weeks that subjects took medication (P less than 0.01)

The main finding from the analysis of immune parameters, was that after 8 and 16 weeks of intervention, salivary IgA concentrations were higher in the probiotic group compared to the placebo group (P = 0.03).

Subject dropout was mainly due to air travel to competitions, injury or persistent illness. These prevented the subjects either being able to take the drinks or undertake the minimum level of training required for the study. Blinding was shown to be effective.


The authors concluded that regular ingestion of the probiotic (LcS) appeared to be beneficial in reducing the frequency of URTI in this group of athletes. The data indicated that this benefit might be related to better maintenance of salivary IgA in the athletes taking the probiotic, reducing the negative effects of regular intense sports training during winter.

Fuskevåg O-M et al (2012)

Lactobacillus casei Shirota modulation of ammonia metabolism in physical exercise. Int J Probiotics & Prebiotics 7(1):13-16.

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During exercise, ammonia is generated as a natural metabolic waste product, normally excreted via the kidneys after conversion into urea in the liver. If the exercise is strenuous, blood ammonia levels can build up and exceed the liver's capacity to remove it. This can cause ammonia levels to increase in the brain, and if this happens the ammonia is removed through the astrocytes through the enzymatic activity of glutamine synthetase, which combines ammonia with glutamate to produce glutamine. Osmotic stress may be induced by the subsequent increase in intracellular glutamine, however, leading to water accumulation, potentially mild encephalopathy and impaired cognitive function.

Successful treatment with a phenylacetate precursor has been used in patients suffering urea cycle disorders and raised levels of ammonia in the blood. Phenylacetate forms a stable conjugate with glutamine to make phenylglutamine (PAG) which can be readily excreted via the kidneys.


As lactobacilli can metabolise phenylalanine into phenylacetate, the study was based on the hypothesis that supplementation with L. casei Shirota could help to regulate ammonia metabolism in healthy people undertaking strenuous exercise via the natural generation of phenylacetate by the probiotic. This would enable ammonia, trapped as glutamine, to be excreted as phenylacetylglutamine via the kidneys.


An open-label, pilot, proof of principle study was conducted in 20 male football players assigned to consume either probiotic (L. casei Shirota; minimum 6.5x109 twice per day) or no supplementation. The players undertook an exhaustive routine designed to exercise all the major muscle blocks (two cycles of a 9-station static exercise program with a one minute rest between the two cycles; water supplied ad libertum). The players provided a four hour timed urine sample after the exercise program. Both the exercise program and urine sampling were repeated after one month. Urine samples were measured for phenyacetylglutamine and ammonia and corrected by creatinine levels.


The results (expressed as the difference in urinary levels for each volunteer between the two sampling points) showed that phenylacetylglutamine significantly increased in the probiotic group (2.98 ±1.04 vs -0.911 ±0.477; P less than 0.01) and, while not reaching statistical significance, their ammonia levels were also lower compared to the control group (0.953 ± 0.868 vs 1.486 ± 0.865; P=0.064).


The researchers concluded that probiotic supplementation with a probiotic Lactobacillus strain appeared to help regulate exercise-generated ammonia in young health sportsmen.

Available Papers

Gleeson et al (2011) Daily probiotic’s (Lactobacillus casei Shirota) reduction of infection incidence in athletes

Fuskevåg et al (2012) Lactobacillus casei Shirota modulation of ammonia metabolism in physical exercise.

Gleeson (2008) The effect of 14 days supplementation with Yakult probiotic on circulating hormonal, leukocyte, and cytokine responses to prolonged cycling in man

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