. 2022 Dec 7;9:1003620. doi: 10.3389/fnut.2022.1003620

Table 6.

Systematic review study outcomes for included studies that investigated the impact of prebiotic, probiotic and synbiotic supplementation on markers of EIGS in response to an acute exercise bout.

References	n and study design	Supplement/ comparator	Intervention ingredient/s and supplement duration	Exercise protocol	Outcome measure/s (Δ in mean/median from pre-exercise to immediately post-exercise unless otherwise indicated)
Intestinal permeability
Axelrod et al. (63)	n = 7 RXT	Probiotic vs. placebo	L. salivarius UCC118, 4 wk	Treadmill running: 2 h at 60% VO_2max. Tamb: 25°C, RH: 31%	Sucrose permeability (Δ in iAUC from baseline): Int ↓ 38%, Pla ↑ 169% (p = 0.029) Rhamnose permeability (Δ in iAUC from baseline): Int ↓ 0.1-fold, Pla ↑ 0.5-fold ^NS Lactulose permeability (Δ in iAUC from baseline): Int ↓ 0.1-fold, Pla ↑ 0.4-fold ^NS L/R Ratio (Δ in iAUC from baseline): ^NS (data not reported)
Pugh et al. (79)	n = 24 RCT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Non-sanctioned marathon (outdoor running track). Finish time: Int: 234 ± 38 min, Pla: 247 ± 47 ^NS % LT: Int: 90.2 ± 9.1, Pla: 91.3 ± 8.7 ^NS T_amb: 16–17°C; Wind: 8–16 km/h	Serum L/R ratio (Δ from baseline test): Int ↑ 0.04, Pla ↑ 0.02 ^NS
Pugh et al. (100)	n = 7 RXT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Cycle ergometer: 2 h at 55% W_max followed by 100 kJ time trial. Ambient conditions not stated.	Serum L/R ratio (Δ from baseline test): Int ↑ 0.045, Pla ↑ 0.052 ^NS
Shing et al. (102)	n = 10 RXT	Probiotic vs. placebo	L. acidophilus, L. rhamnosus, L. casei, L. plantarum, L. fermentum, B. lactis, B. breve, B. bifidum, S. thermophilus, 4 wk	Treadmill running: time to fatigue at 80% ventilatory threshold. Tamb: 35°C, RH: 40%	Urinary L/R ratio: 8% lower following Int cf Pla ^NS–other data not reported
Roberts et al. (94)	n = 20 RCT	Synbiotic vs. placebo	L. acidophilus CUL-60 (NCIMB 30157), L. acidophillus CUL-21 (NCIMB 30156), B. bifidum CUL-20 (NCIMB 30172), B. animalis subspecies lactis CUL-34 (NCIMB 30153), Fructooligosaccharides, 12 wk	Ironman triathlon. Mean finish time: Int: 12 h 47 min, Pla: 14 h 12 min ^NS	Urinary lactulose/mannitol ratio (Δ from pre- to 6 d post-race): Int ↑ 0.005, Pla ↑ 0.020 ^NS
Intestinal injury
Pugh et al. (79)	n = 24 RCT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Non-sanctioned marathon (outdoor running track). Finish time: Int: 234 ± 38 min, Pla: 247 ± 47 ^NS % LT: Int: 90.2 ± 9.1, Pla: 91.3 ± 8.7 ^NS T_amb: 16–17°C; Wind: 8–16 km/h	Serum I-FABP: Int ↑ 1,359 pg/mL, Pla ↑ 932 pg/mL ^NS
Pugh et al. (100)	n = 7 RXT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Cycle ergometer: 2 h at 55% W_max followed by 100 kJ time trial. Ambient conditions not stated.	Plasma I-FABP: Post-exercise: Int ↓ 207 pg/mL, Pla ↓ 295 pg/mL ^NS 1 h post-exercise: Int ↓ 182 pg/mL, Pla ↓ 263 pg/mL ^NS
Shing et al. (102)	n = 10 RXT	Probiotic vs. placebo	L. acidophilus, L. rhamnosus, L. casei, L. plantarum, L. fermentum, B. lactis, B. breve, B. bifidum, S. thermophilus, 4 wk	Treadmill running: time to fatigue at 80% ventilatory threshold. Tamb: 35°C, RH: 40%	Urinary Claudin 3 (absolute values): Int 6.1 ± 3.3 ng/mmol creatinine, Pla 8.1 ± 5.1 ng/mmol creatinine ^NS
Bacterial endotoxin responses
Gill et al. (68)	n = 8 RXT	Probiotic vs. placebo	L. casei, 7 days	Treadmill running: 2 h at 60% VO_2max. Tamb: 34°C, RH: 32%	Gram-negative bacterial endotoxin (ΔPre-ex - 1-h Post-ex): Int ↑ 0.5 EU/mL (23%), Pla ↓ 0.2 EU/mL (8%) (p = 0.05)
Shing et al. (102)	n = 10 RXT	Probiotic vs. placebo	L. acidophilus, L. rhamnosus, L. casei, L. plantarum, L. fermentum, B. lactis, B. breve, B. bifidum, S. thermophilus, 4 wk	Treadmill running: time to fatigue at 80% ventilatory threshold. Tamb: 35°C, RH: 40%	Serum LPS: Int ↑ 0.03 EU, Pla ↑ 0.05 EU ^NS Anti-LPS IgM: Int ↓ 1.0 MU/mL, Pla ↑ 0.3 MU/mL ^NS
Roberts et al. (94)	n = 20 RCT	Synbiotic vs. placebo	L. acidophilus CUL-60 (NCIMB 30157), L. acidophillus CUL-21 (NCIMB 30156), B. bifidum CUL-20 (NCIMB 30172), B. animalis subspecies lactis CUL-34 (NCIMB 30153), Fructooligosaccharides, 12 wk	Ironman triathlon. Mean finish time: Int: 12 h 47 min, Pla: 14 h 12 min ^NS	Endotoxin units (Δ from pre- to 6 d post-exercise): Int ↓ 1.6 pg/mL (p = 0.047), Pla ↓ 0.44 pg/mL ^NS Anti-LPS IgG (Δ from pre- to 6 d post-exercise): Int ↓ 90 MU/mL, Pla ↑ 27 MU/mL ^NS
Cytokine responses
Axelrod et al. (63)	n = 7 RXT	Probiotic vs. placebo	L. salivarius UCC118, 4 wk	Treadmill running: 2 h at 60% VO_2max. Tamb: 25°C, RH: 31%	IL-6: (ΔΔ pre to post-exercise, pre to post-intervention) Int ↑ 0.5 pg/mL, Pla ↑ 1.4 pg/mL ^NS
Batatinha et al. (65)	n =27 RCT	Probiotic vs. placebo	B. animalis. Lactis 10 × 10⁹; L. Acidophilus 10 × 10⁹ 1 sachet daily for 30 days	Marathon race: Race time was 4.08 ± 0.55 h T_abm not stated	IL-10: Int: ↑ 254 ng/ml, Pla: ↑ 219 ng/ml ^NS IL-4: Int: ↑ 6.9 ng/ml, Pla:↑ 2.2 ng/ml ^NS IL-6: Int: ↑ 14.0 ng/ml, Pla: ↑ 14.1 ng/ml ^NS IL-2: Int: ↓ 2.6 ng/ml, Pla: ↓ 0.3ng/ml ^NS IL-15: Int: ↓ 0.7 ng/ml, Pla: ↓ 0.5 ng/ml ^NS IL-8: Int: ↑ 7.1 ng/ml, Pla: ↑ 10.4 ng/ml ^NS IL-1β: Int: ↓ 1.1 ng/ml, Pla: ↑ 0.1 ng/ml ^NS TNF-α: Int: ↑ 3.9 ng/ml, Pla: ↑ 3.8 ng/ml ^NS IFN-γ: Int: ↓ 5.3 ng/ml, Pla: ↓ 2.8 ng/ml ^NS
Gill et al. (68)	n = 8 RXT	Probiotic vs. placebo	L. casei, 7 days	Treadmill running: 2 h at 60% VO_2max. Tamb: 34°C, RH: 32%	IL-6: Post-exercise: Int ↑ 3.6 pg/mL, Pla ↑ 3.1 pg/mL ^NS 1 h post-exercise: Int ↑ 2.1 pg/mL, Pla ↑ 1.2 pg/mL ^NS 2 h post-exercise: Int ↑ 1.1 pg/mL, Pla ↑ 0.4 pg/mL ^NS 4 h post-exercise: Int ↑ 0.4 pg/mL, Pla ↔ 0.0 pg/mL ^NS 24 h post-exercise: Int ↔ 0.0 pg/mL, Pla ↓ 0.3 pg/mL ^NS IL-1β: Post-exercise: Int ↑ 0.09 pg/mL, Pla ↑ 0.02 pg/mL ^NS 1 h post-exercise: Int ↑ 0.03 pg/mL, Pla ↓ 0.03 pg/mL ^NS 2 h post-exercise: Int ↓ 0.01 pg/mL, Pla ↓ 0.01 pg/mL ^NS 4 h post-exercise: Int ↓ 0.01 pg/mL, Pla ↓ 0.01 pg/mL ^NS 24 h post-exercise: Int ↑ 0.02 pg/mL, Pla ↔ 0.0 pg/mL ^NS TNF-a: Post-exercise: Int ↑ 0.5 pg/mL, Pla ↑ 0.3 pg/mL ^NS 1 h post-exercise: Int ↑ 0.3 pg/mL, Pla ↓ 0.3 pg/mL ^NS 2 h post-exercise: Int ↔ 0.0 pg/mL, Pla ↓ 0.4 pg/mL ^NS 4 h post-exercise: Int ↑ 0.1 pg/mL, Pla ↓ 0.3 pg/mL ^NS 24 h post-exercise: Int ↑ 0.3 pg/mL, Pla ↑ 0.1 pg/mL ^NS
					IFN-γ: Post-exercise: Int ↔ 0.0 pg/mL, Pla ↑ 0.1 pg/mL ^NS 1 h post-exercise: Int ↓ 0.1 pg/mL, Pla ↓ 0.2 pg/mL ^NS 2 h post-exercise: Int ↓ 0.3 pg/mL, Pla ↓ 0.4 pg/mL ^NS 4 h post-exercise: Int ↑ 0.3 pg/mL, Pla ↓ 0.4 pg/mL ^NS 24 h post-exercise: Int ↑ 0.2 pg/mL, Pla ↔ 0.0 pg/mL ^NS IL-10: Post-exercise: Int ↑ 10.8 pg/mL, Pla ↑ 7.2 pg/mL ^NS 1 h post-exercise: Int ↑ 10.6 pg/mL, Pla ↑ 9.0 pg/mL ^NS 2 h post-exercise: Int ↑ 2.8 pg/mL, Pla ↑ 2.7 pg/mL ^NS 4 h post-exercise: Int ↓ 0.1 pg/mL, Pla ↔ 0.0 pg/mL ^NS 24 h post-exercise: Int ↔ 0.0 pg/mL, Pla ↑ 0.2 pg/mL ^NS IL-8: Post-exercise: Int ↑ 1.8 pg/mL, Pla ↑ 1.2 pg/mL ^NS 1 h post-exercise: Int ↑ 1.1 pg/mL, Pla ↑ 0.6 pg/mL ^NS 2 h post-exercise: Int ↑ 0.1 pg/mL, Pla ↑ 0.1 pg/mL ^NS 4 h post-exercise: Int ↔ 0.0 pg/mL, Pla ↓ 0.1 pg/mL ^NS 24 h post-exercise: Int ↓ 0.1 pg/mL, Pla ↓ 0.4 pg/mL ^NS
Lamprecht et al.	n = 23 RCT	Probiotic vs. placebo	B. bifidum W23, B lactis W51, E. faecium W54, L. acidophilus W22, L. brevis W63, L. lactis W58, 14 wk	3 x incremental “step” tests on cycling ergometer to exhaustion, with 15 min active recovery between each test. Total test time ~80–90 min. T_amb: 20°C, RH: 60% RH	IL-6: Int ↑ 3.3 pg/mL, Pla ↑ 1.9 pg/mL ^NS TNF-α: Int ↑ 2.3 pg/mL, Pla ↑ 0.24 pg/mL ^NS
Pugh et al. (79)	n = 24 RCT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Non-sanctioned marathon (outdoor running track). Finish time: Int: 234 ± 38 min, Pla: 247 ± 47 ^NS % LT: Int: 90.2 ± 9.1, Pla: 91.3 ± 8.7 ^NS T_amb: 16–17°C; Wind: 8–16 km/h	Serum CD14: Int ↑ 5.9 μg/mL, Pla ↑ 5.4 μg/mL ^NS IL-6: Int ↑ 9.95 μg/mL, Pla ↑ 12.76 μg/mL ^NS IL-8: Int ↑ 11.21 μg/mL, Pla ↑ 9.98 μg/mL ^NS IL-10: Int ↑ 4.36 μg/mL, Pla ↑ 5.05 μg/mL ^NS
Pugh et al. (100)	n = 7 RXT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Cycle ergometer: 2 h at 55% W_max followed by 100 kJ time trial. Ambient conditions not stated.	IL-1α: Int ↑ 1.15 μg/mL, Pla ↑ 0.45 μg/mL ^NS IL-6: Int ↑ 1.05 μg/mL, Pla ↑ 1.37 μg/mL ^NS IL-8: Int ↑ 1.96 μg/mL, Pla ↑ 2.21 μg/mL ^NS IL-10: Int ↑ 2.11 μg/mL, Pla ↑ 1.18 μg/mL ^NS
Shing et al. (102)	n = 10 RXT	Probiotic vs. placebo	L. acidophilus, L. rhamnosus, L. casei, L. plantarum, L. fermentum, B. lactis, B. breve, B. bifidum, S. thermophilus, 4 wk	Treadmill running: time to fatigue at 80% ventilatory threshold. Tamb: 35°C, RH: 40%	IL-1ra: Post-exercise: Int ↑ 74 pg/mL, Pla ↑ 79 pg/mL ^NS 1 h post-exercise: Int ↑ 183 pg/mL, Pla ↑ 188 pg/mL ^NS TNF-α: Post-exercise: Int ↑ 0.62 pg/mL, Pla ↑ 1.65 pg/mL ^NS 1 h post-exercise: Int ↓ 0.33 pg/mL, Pla ↑ 1.47 pg/mL ^NS
					IL-6: Post-exercise: Int ↑ 0.91 pg/mL, Pla ↑ 1.32 pg/mL ^NS 1 h post-exercise: Int ↑ 1.04 pg/mL, Pla ↑ 1.45 pg/mL ^NS IL-10: Post-exercise: Int ↑ 1.96 pg/mL, Pla ↓ 0.22 pg/mL ^NS 1 h post-exercise: Int ↑ 7.61 pg/mL, Pla ↑ 9.89 pg/mL ^NS Neutrophil elastase: Post-exercise: Int ↓ 269 fg/cell, Pla ↑ 74 fg/cell ^NS 1 h post-exercise: Int ↓ 259 fg/cell, Pla ↓ 12 fg/cell ^NS
Tavares-Silva et al. (87)	n = 14 RCT	Probiotic vs. placebo	Lactobacillus acidophilus-LB-G80, Lactobacillus paracasei-LPc-G110, Lactococcus subp. lactis-LLL-G25, Bifidobacterium animalis subp. lactis-BL-G101, Bifidobacterium bifidum-BB-G90 5 × 10⁹ CFU 2.0 g/day for 30 days	Marathon race Race Time (min) Pla: 243.0 ± 33.73 Int: 252.87 ± 39.77 ^NS Difference Tamb: 21.5°C, RH: 67%.	All changes relative to 24 h pre resting value IL-2 Post-ex: Pla: ↑ 0.01 pg/ml ^NS, Int: ↑0.06 pg/ml ^NS 1 h post-ex.: Pla: ↓ 0.05 pg/ml ^NS, Int: ↑ 0.11 pg/ml ^NS IL-4 Post-ex: Pla: ↑0.59 pg/ml ^NS, Int: ↑0.32 pg/ml ^NS 1 h post-ex.: Pla: ↓ 0.05 pg/ml ^NS, Int: ↑0.21 pg/ml ^NS IL-10 Post-ex : Pla: ↑ 1.05 pg/ml (p < 0.05), Int: ↑1.31 pg/ml^NS 1 h post-ex.: Pla: ↑ 0.7 pg/ml ^NS, Int: ↑ 1.3 pg/ml (p < 0.05) TNF-α Post-ex: Pla: ↑0.99 pg/ml (p < 0.05), Int: ↑1.2 pg/ml (p < 0.05) 1 h post-ex: Pla: ↑ 1.1 pg/ml (p < 0.05), Int: ↑ 0.2 pg/ml ^NS
Vaisberg et al. (89)	n = 42 RCT	Probiotic vs. placebo	Lactobacillus casei Shirota, 30 days	Marathon race Ambient conditions not stated	IL-1β: Int ↑↓1.8 pg/mL^NS, Pla ↑13.5 pg/mL ^NS IL-1ra: Int ↑18.7 pg/mL^NS, Pla ↑ 24.7 pg/mL p < 0.01 IL-4: Int ↑1.4 pg/mL^NS, Pla ↑ 6.6 pg/mL ^NS IL-5: Int ↑3.1 pg/mL^NS, Pla ↓ 34.5 ↑ 31.8 pg/mL ^NS IL-6: Int ↑ 34.8 pg/mLp < 0.01, Pla ↑ 36.5 pg/mL p < 0.001 IL-10: Int ↑ 15.0 pg/mL p < 0.01, Pla ↑ 19.0 pg/mL p < 0.01 IL-12p70: Int ↑ 19.2 pg/mL p < 0.05, Pla ↑ 23.0 pg/mL p < 0.01 IL-13: Int ↑ 2.1 pg/mL^NS, Pla ↑ 1.2 pg/mL ^NS TNF-α: Int ↑ 20.0 pg/mL^NS, Pla ↑ 123.4 pg/mLp < 0.05 Pla > Int, p < 0.01 between groups
West et al. (90)	n = 88 RCT	Probiotic vs. placebo	Lactobacillus fermentum VRI-003 PCC^®, 11 wk	Incremental cycling ergometer test (VO_2max protocol). Ambient conditions not stated	Factor changes in acute post-exercise cytokine responses: IL-1ra: Male: Int 0.84, Pla 1.39 (very likely ↓) Female: Int 0.80, Pla 1.88 (very likely ↓)
					IL-10: Male: Int 0.95, Pla 1.16 (possible ↓) Female: Int 0.89, Pla 1.45 (possible ↓) IL-6: Male: Int 0.92, Pla 1.22 (likely ↓) Female: Int 0.71, Pla 2.29 (likely ↓) IL-8: Male: Int 0.80, Pla 0.87 (unclear) Female: Int 0.71, Pla 1.15 (probably ↓) GM-CSF: Male: Int 0.78, Pla 1.75 (very likely ↓) Female: Int 0.85, Pla 3.3 (very likely ↓) IFN-γ: Male: Int 1.2, Pla 1.49 (likely ↓) Female: Int 1.07, Pla 1.56 (likely ↓) TNF-α: Male: Int 1.27, Pla 1.66 (likely ↓) Female: Int 1.15, Pla 1.72 (likely ↓)
Short chain fatty acids
Valle et al. (96)	n = 65 RCT	Synbiotic vs. Placebo	Lactobacillus acidophilus LA-5, Bifidobacterium animalis BB-12, Inulin 2.3 g 60 g serve of ice cream, daily for 30 days	5 d military training, including physical and psychological exhaustion, marching 8–20 km, carrying ~ 30 kg equipment, sleep deprivation. Subject to various weather extremes.	Fecal acetate (mmol/L): Pla: Pre: 3·07 ± 1·64, Post: OR 0·16, 95%CI −0·25, 0·57 Post-training: OR −0·71, 95%CI−1·08, −0·34 Int: Pre: 2·82 ± 1·78 Post: OR 0·34, 95%CI −0·06, 0·74 Post-training: OR −0·80, 95%CI −1·14, −0·46 Main effect of time, P < 0·001 ^NS between groups Fecal proprionate (mmol/L): Pla: Pre: 0·97 ± 0·61, Post: OR 0·31, 95%CI −0·02, 0·63 Post-training: OR−0·08, 95%CI −0·24, 0·08 Int: Pre: 0·83 ± 0·50 Post: OR 0·20, 95%CI −0·01, 0·41 Post-training: OR −0·12, 95%CI −0·26, 0·02 Main effect of time, P = 0·004 ^NS between groups Fecal butyrate (mmol/L): Pla: Pre: 1·18 ± 0·85 Post: OR 0·25, 95%CI −0·03, 0·47 Post-training: OR −0·09, 95%CI −0·28, 0·10 Int: Pre: 1·04 ± 0·73 Post: OR 0·39, 95%CI 0·20, 0·59 Post-training: OR −0·17, 95%CI −0·33 −0·01 Main effect of time, P = 0·002 ^NS between groups
Bacterial taxa
Valle et al. (96)	n = 65 RCT	Synbiotic vs. Placebo	Lactobacillus acidophilus LA-5, Bifidobacterium animalis BB-12, Inulin 2.3 g 60 g serve of ice cream, daily for 30 days	5 d military training, including physical and psychological exhaustion, marching 8–20 km, carrying ~ 30 kg equipment, sleep deprivation. Subject to various weather extremes.	16S gene sequencing α - Diversity (Shannon index): Int:↑ 0.119 Pla: ↓ 0.095 ^NS α - Diversity (Simpson index): Int: ↑ 0.015, Pla: ↓ 0.021 ^NS ^NS group by time effect ^NS α-diversity between groups or periods
Gastrointestinal symptoms
Kekkonen et al. (99)	n = 119 RCT	Probiotic vs. placebo	L. rhamnosus GG, 3 months	Helsinki Marathon Finish time: Int: 3 h 32 min (range 2 h 24 min to 4 h 35 min) Pla: 3 h 30 min (range 2 h 52 min to 4 h 19 min) ^NS between groups Ambient conditions not specified.	During training period: Subjects with GIS episodes: Int 27%, Pla 30% ^NS No. of GIS episodes/subject: Int 0.4, Pla 0.6 ^NS GIS episode duration: Int 2.9 days, Pla 4.2 days ^NS During 2 wk after marathon: Subjects with GIS episodes: Int: 6%, Pla: 6% ^NS No. of GIS episodes/subject: Int 0.1, Pla 0.1 ^NS GIS episode duration: Int 1.0 days, Pla 2.3 days (p < 0.05)
Pugh et al. (79)	n = 24 RCT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Non-sanctioned marathon (outdoor running track). Finish time: Int: 234 ± 38 min, Pla: 247 ± 47 ^NS % LT: Int: 90.2 ± 9.1, Pla: 91.3 ± 8.7 ^NS T_amb: 16–17°C; Wind: 8–16 km/h	Global GIS score during marathon (median): 1st third: Int 1.3, Pla 1.6 ^NS 2nd third: Int 3.0, Pla 3.2 ^NS 3rd third: Int 3.5, Pla 6.1 (p = 0.01) GIS Score Post-Race (median): Total GIS: Int: 13, Pla 15 ^NS Lower GIS: Int 10, Pla 7 ^NS Upper GIS: Int 6, Pla 5 ^NS GIS Score 24 h Post-Race (median): Total GIS: Int 16, Pla 12 ^NS Lower GIS: Int 7, Pla 5 ^NS Upper GIS: Int 6, Pla 4 ^NS
Pugh et al. (100)	n = 7 RXT	Probiotic vs. placebo	L. acidophilus CUL60 L. acidophilus CUL21 B. bifidum CUL20 B. animalis subsp. Lactis CUL34, 4 wk	Cycle ergometer: 2 h at 55% W_max followed by 100 kJ time trial. Ambient conditions not stated.	^NS between. trials, data not reported
Schreiber et al. (82)	n = 27 RCT	Probiotic vs. placebo	l. helveticus Lafti L10, b. animalis ssp. lactis Lafti B94, e. faecium R0026, b. longum R0175, Bacillus subtilis R0179, 90 days	Evaluation (online survey) at training, competition, and during the first 2 h recovery from training or competition.	GIS incidence by slider questionnaire: GIS incidence during training (ΔGI): Int: −27 ± 47%, Pla: 8 ± 29%, Int < Pla, P = 0.04, d = 0.9 GIS incidence during competition (ΔGI): Int: 0 ± 47%, Pla: 9 ± 30%, ^NS GIS incidence after training (ΔGI): Int: −10 ± 32%, Pla: 9 ± 54%, ^NS GIS incidence after competition (ΔGI): Int: −20 ± 42%, Pla: 9 ± 54%, ^NS
Shing et al. (102)	n = 10 RXT	Probiotic vs. placebo	L. acidophilus, L. rhamnosus, L. casei, L. plantarum, L. fermentum, B. lactis, B. breve, B. bifidum, S. thermophilus, 4 wk	Treadmill running: time to fatigue at 80% ventilatory threshold. Tamb: 35°C, RH: 40%	GIS Symptom Severity Score: Int: 1.4, Pla 1.6 ^NS
Valle et al. (96)	n = 65 RCT	Synbiotic vs. Placebo	Lactobacillus acidophilus LA-5, Bifidobacterium animalis BB-12, Inulin, 2.3 g, 30 days	5 d military training, including physical and psychological exhaustion, marching 8–20 km, carrying ~ 30 kg equipment, sleep deprivation. Subject to various weather extremes.	GIS Sum of different symptoms: Int: pre: 8.06 ± 5.65 Δ Post-supp.: OR −2.24, 95%CI −3.15, −1.34 Δ Post-military training: OR −4.31, 95%CI −5.31, −3.30 P < 0.05, Δ post-supplementation v. Δ post-military training. Pla: pre: 8.48 ± 5.09 Δ Post-supp.: OR −1.16, 95%CI −2.51, 0.18 Δ Post-military training: OR −3.91, 95%CI −5.01, −2.82 P < 0.05, Δ post-supplementation v. Δ post-military training ^NS Group × time effect “Both groups showed a decreased number of gastrointestinal symptoms at post-military training (P < 0·001; main effect of time) with no differences between them (P = 0·37; group × time effect)”

Int, Intervention; Pla, Placebo; RCT, Randomized control trial; RXT, Randomized crossover trial; I-FABP, Intestinal fatty acid binding protein; NS, No significant difference between groups/trials; LPS, Lipopolysaccharide; wk, week.