RESUMEN
CONTEXT: Two-thirds of an individual's gut microbiota is unique and influenced by dietary and exercise habits, age, sex, genetics, ethnicity, antibiotics, health, and disease. It plays important roles in nutrient and vitamin metabolism, inflammatory modulation, immune system function, and overall health of an individual. Specifically, in sports it may help decrease recovery time and improve athletic performance. EVIDENCE ACQUISITION: PubMed and Medline databases were used for the literature search. Bibliographies based on the original search were utilized to pursue further literature search. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 4. RESULTS: Diet and exercise play very important roles in the composition of the gut microbiota in the athletic and nonathletic individual. Ingestion of carbohydrates during and after exercise seems to have an anti-inflammatory effect postexercise. Supplementation with probiotic seems to aid in recovery after exercise, too, especially restoring the "normal" gut microbiota. Physically active individuals of all levels have more alpha diversity and "health-promoting gut species" in their microbiome than nonactive individuals, along with higher concentrations of short-chain fatty acids (SCFA) and SCFA-producing organisms. However, exercise interventions should be longer than 8 weeks to see these positive characteristics. Immune function is highly influenced by the gut microbiota's response to exercise. A transient immune dysfunction occurs after prolonged high-intensity exercise, which correlates with microbiota dysregulation. Nevertheless, long-term exposure to exercise will enhance the immune response and lead to positive changes in the gut microbiota. CONCLUSION: Although the exact mechanisms of the effects that diet, exercise, and genetics have on the gut microbiota remain largely unknown, there is evidence that suggests overall health benefits. In the athletic population, these benefits can ultimately lead to performance improvement.