TABLE 1.
Combined diet, exercise, and gut microbiota interventions in athletes1
| Study (reference) | Year | Diet/supplement | Exercise/test | Duration | Participants | Microbiota effects | Metabolite effects | Metabolic effects | Performance effects |
|---|---|---|---|---|---|---|---|---|---|
| Moreno-Pérez et al. (37) | 2018 | Protein supplement (10 g whey isolate + 10 g beef hydrosylate) vs. control (maltodextrin) | Habitual training (≥5× per week) | 10 wk | 24 males, ages 18–45 y, cross-country runners | ↑ Bacteroidetes in protein group; ↓ Roseburia, Blautia, Bif. longum in protein group | ↔ Fecal pH, water content, ammonia, SCFA concentration, plasma or urine malondialdehyde in protein group | — | — |
| Murtaza et al. (38) | 2019 | HCHO vs. PCHO vs. LCHF | Habitual training test: VO2peak, walking economy, 10-km race time, 25-km long walk time, respiratory exchange ratio, fuel oxidation rate | 3 wk | 21 males, ages 20–35 y, race walkers | ↔ Enterotype, diversity (Shannon, Simpson, weighted/unweighted UniFrac) in diet groups; ↓ Faecalibacterium spp., Bifidobacterium, Veillonella, Streptococcus, Succinivibrio, Odoribacter, Lachnospira spp. in LCHF group; ↑ Dorea spp., Bacteroides spp., Enterobacteriaceae, Peptostreptococcaceae, Barnesiellaceae, Akkermansia in LCHF group; LCHF × enterotype interaction (↓ Bif., ↑ Sutterella in Bacteroides enterotype; ↑ Clostridiales in Prevotella enterotype); ↑ Clostridiales, Ruminococcaceae, Coprococcus spp., Akkermansia muciniphila, Bifidobacterium, Streptococcus in PCHO group; ↑ Clostridiaceae, Lachnospiraceae, Ruminococcaceae, Streptophyta in HCHO group | — | ↑ Fat oxidation in LCHF group Bacteroides ∼ fat oxidation (–) in LCHF group | ↓ Exercise economy, 10-km race performance in LCHF group; ↑ exercise economy, 10-km race performance in HCHO and PCHO groups; Dorea ∼ exercise economy (–) in LCHF group |
| Karl et al. (39) | 2017 | Rations (control) vs. rations + protein supplement (whey) vs. rations + carbohydrate supplement | 4-d cross-country ski-march (STRESS) | 4 d | 73 soldiers, age >18 y, 71 men, 2 women | ↑ α-Diversity (Shannon) post STRESS (no difference between groups); ↔ richness (Chao1, total observed OTUs); ↑ Firmicutes/Bacteroidetes ratio post STRESS (no difference between groups) | ↑ p-Cresol post STRESS (no difference between groups) | ↑ Sucralose and mannitol excretion post STRESS (no difference between groups); ↔ LPS | — |
| Son et al. (40) | 2020 | Probiotic supplement (1012 CFU each Lactobacillus acidophilus, L. casei, L. helveticus, Bifidobacterium bifidum) vs. placebo; divided into groups based on dietary intake: group 1 (high-protein, reduced fiber), group 2 (high-protein, adequate fiber), group 3 (adequate protein, restricted fiber), group 4 (sedentary control) | Habitual training | 60 d | 15 males, bodybuilders | ↔ α-Diversity (Shannon, Simpson), probiotic bacteria (Lactobacilli, Bifidobacterium) in probiotic vs. placebo group; ↑ Paraprevotella in probiotic group; ↑ Megamonas, Anaerostipes, Dorea in placebo group; ↔ α-diversity in group 1 vs. group 4; ↑ no. of species, Chao1 richness, ACE, Jacknife in groups 2 and 3 vs. group 4; ↑ Haemophilus, Streptococcus in group 1; ↑ Bifidobacterium in group 2; ↑ Faecalibacterium in group 3 | ↔ SCFAs | — | — |
| Huang et al. (41) | 2020 | Probiotic supplement (3× 1010 CFU/d L. plantarum 128) vs. placebo | Habitual training test:  , endurance performance |
4 wk | 20 males, triathletes | ↑ Akkermansia, Bifidobacterium, Butyricimonas, Lactobacilli in Probiotic group; ↓ α-diversity (Shannon), Anaerotruncus, Caproiciproducens, Coprobacillus, Desulfovibrio, Dielma, Family_XIII, Holdemania, Oxalobacter in Probiotic group; ↔ Firmicutes/Bacteroidetes ratio | ↑ SCFAs (acetate, propionate, butyrate) in probiotic group | ↔ Body composition (bone, fat, lean %), blood biochemistry (glucose, lipids, creatinine, liver enzymes, blood cell counts) | ↔  ; ↑ endurance performance |
| Martarelli et al. (42) | 2011 | Probiotic supplement (109 CFU/d, 1:1 of L. rhamnosus IMC 501, L. paracasei IMC 502) vs. control (no supplement); all athletes on controlled diet developed based on athlete's basal metabolism, body composition, and energy expenditure (methods not described) | Controlled training developed based on athlete's basal metabolism, body composition and energy expenditure (methods not described) | 4 wk | 24 males, cyclists | ↑ Lactobacilli in Probiotic group | — | ↑ Reactive oxygen metabolites after physical activity in control group (not in probiotic group); ↑ plasma antioxidants in probiotic group | — |
| West et al. (43) | 2011 | Probiotic supplement (109 CFU/d L. fermentum PCC) vs. placebo | Habitual training test:  , peak power output, postexercise cytokine response |
11 wk | 64 males, 35 females, cyclists | ↑ Lactobacilli in males in probiotic group (not in females)—obtained from subset of 10 males and 10 females from each group | — | ↓ Severity of GI and lower respiratory illness in males in probiotic vs. placebo; ↑ number and duration (↓ severity) of lower respiratory illness in females in probiotic vs. placebo; ↓ cytokine response to acute exercise in probiotic group; ↔ upper respiratory tract infection, mucosal immunity (lactoferrin, lysozyme, SIgA) | ↔ 
|
| Axelrod et al. (44) | 2020 | Probiotic supplement (2× 108 CFU/d L. salivarius UCC118) vs. placebo | Test 2-h treadmill at 60% 
|
4 wk | 7 trained endurance athletes, ages 18–45 y | ↓ Verrumicrobia, Verrumicrobiae, Verrumicrobiales, Verrumicrobiaceae, Prosthecobacter fusiformis in Probiotic group; ↔ diversity/richness (Chao1, ACE, Shannon, Simpson) | — | ↓ GI permeability of sucrose in probiotic group; ↔ lactulose and rhamnose excretion, fecal zonulin, core temperature, IL-6 | — |
1
ACE, Abundance-based Coverage Estimator;Bif., Bifidobacterium; GI, gastrointestinal; HCHO, high carbohydrate; LCHF, ketogenic low-carbohydrate, high-fat; OTU, operational taxonomic unit; PCHO, periodized carbohydrate; SIgA, secretory immunoglobulin A; STRESS, 4-d cross-country ski march, 
, maximal oxygen uptake; VO2peak, peak oxygen uptake; ↑, significant increase; ↓, significant decrease; ↔, no significant difference.