Prolonged and intense exercise may have the potential to suppress the immune system, and impair sports performance. Clinical evidence has also shown that strenuous training may induce anxiety and stress as well as having a potential impact on gastrointestinal health.
The benefits of taking probiotics to improve sports performance have been showcased by many investigators. In terms of their impact on the psychological health of athletes, many studies have focused on the effects of probiotics on healthy volunteers but limited studies have been conducted on competitive athletes.
Hence, this study was designed to determine the effects of daily probiotic supplementation on anxiety, stress, mood and fitness levels among competitive badminton players.
This intervention was a randomised, placebo-controlled study involving 30 badminton players aged 18 to 30 from Universiti Teknologi MARA (UiTM) in Shah Alam, Malaysia. Participants were randomly divided into a probiotic group (PG, Lactobacillus casei at a dose of 3 × 1010 cfu mixed with orange juice) and a control group (CG, orange juice) and were given daily treatments for six weeks.
Tests were undertaken before intervention and after the six weeks. Body parameter data was collected using an InBody 500 bioelectrical impedance analyse, food intake was recorded using three-day records, and anxiety level was determined using the revised competitive state anxiety inventory (CSAI-2R). A 20-minute multi-stage shuttle run test was used to measure aerobic capacity fitness, a handgrip test and a vertical jump test measured hand and leg strength, and a 40-minute dash and t-test measured speed and agility.
After six weeks, the data indicated the anxiety and stress levels of PG players significantly decreased by 16% (p < 0.001) and 20% (p < 0.001), respectively, but there were no significant changes detected in CG players.
Supplementation of probiotics also improved aerobic capacity in PG players by 5.9% (p < 0.001) but did not influence the speed, strength, leg power and agility.
The authors conclude: "Consuming probiotics might significantly help to alleviate competitive anxiety and stress, besides increasing the aerobic capacity of athletes.
"Probiotic supplementation that may influence the regulation of pathways (neuro-endocrine) and mechanism of action in response to physical and psychological stressors encountered by badminton players should further studied. Research evaluating psycho-physiological biomarkers in response to probiotic supplementation may provide greater insight for sports individuals."
Mechanisms of action
The authors state the changes in stress and anxiety following the supplementation of probiotics might be explained by the gut-brain axis (GBA).
Microbiota could decrease stress-induced corticosterone secretion, reducing anxiety and depression-related behaviours by improving the brain expression of gamma-aminobutyric acid (GABA) receptors. In contrast, pathogenic bacteria has been reported to induce anxiety-like behaviors by mediating vagal afferents.
Probiotics may also be capable of triggering GBA responses by transforming dopamine into noradrenaline in the central and peripheral nervous systems, which has been shown to lead to a decrease in depressive behavior.
The authors note that another possible mechanism of microbiota for reducing anxiety is through the hypothalamic-pituitary-adrenal (H.P.A.) axis by enhancing hippocampal neurotrophic factor messenger expression R.N.A., which could decrease anxiety-like activity. Probiotics have also been reported to transform dopamine into noradrenaline in the chromaffin cells of the adrenal medulla, resulting in a decrease in depression-related behavior.
There might be several explanations on how probiotic supplementation improved the aerobic capacity of athletes.
The authors explain: "Microbiota in the gut might play a role in the body’s energy system after a few minutes of muscle contraction, when the phosphocreatine concentration decreases, resulting in the need for other fuels.
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"Gene expression for glycogenolysis would be induced to ensure ATP production for increased muscle activity requirements such as the cross-bridge cycle, myosin ATPase activity, and muscle ion pumps. At the same time, consumption of free fatty acids for oxidation would also increase, enhancing not only the lipolysis of adipose tissues to meet the energy requirement, but also consuming other sources, such as fatty acids from microbiota activity.
"Thus, this would create a reciprocal relationship between the gut microbiota and the energy metabolism of the entire body, which was probably one of the mechanisms by which gut microbiota exerted beneficial effects on athletes’ performance.
"Carbohydrate digestion is a core activity of the human gut microbiota, which drives energy and carbon metabolism in the colon, although the range of protein-generated end products is broader than carbohydrates. In the colon, complex plant-derived polysaccharides, such as cellulose, β-glucan, xylan, mannan and pectin would be digested and subsequently fermented into short-chain fatty acids (SCFAs) by gut microorganisms, which were then used as carbon and energy sources by other specific bacteria such as reductive acetogens, sulfate-reducing bacteria and methanogens."
They also note that probiotic supplementation has been demonstrated to alleviate oxidative stress by reducing the formation of ROS. What's more, probiotic-enriched gut microbiota could promote increased catecholamine activity and thus, minimize exercise-induced fatigue.
Salleh, R.M.; Kuan, G.; Aziz, M.N.A.; Rahim, M.R.A.; Rahayu, T.; Sulaiman, S.; Kusuma, D.W.Y.; Adikari, A.M.G.C.P.; Razam, M.S.M.; Radhakrishnan, A.K.; Appukutty, M.
"Effects of Probiotics on Anxiety, Stress, Mood and Fitness of Badminton Players"
https://doi.org/10.3390/nu13061783 (registering DOI)