The gut and immune system are closely connected, and researchers have found meaningful differences in the gut microbiome of people with COVID-19 compared with healthy controls. These findings have opened an important area of research into how gut health may influence immune resilience, recovery, and long-COVID symptoms.
What Does the Research Show?
Observational studies and systematic reviews have reported lower microbial diversity and shifts in several bacterial groups in people with COVID-19. Some changes appear to persist after recovery, and more recent meta-analyses continue to find associations between gut dysbiosis and disease severity.
Association is not the same as causation. Severe illness, medications, antibiotics, hospitalization, diet changes, age, and other health conditions can all influence the microbiome.
Does the Microbiome Predict COVID Severity?
Some studies have found that lower abundance of bacteria such as Faecalibacterium prausnitzii and certain Bifidobacterium species correlates with more severe disease. These findings are interesting, but they are not ready for use as a clinical microbiome score that predicts an individual person’s outcome.
What About Long COVID?
Persistent microbiome changes have also been reported after acute COVID-19, and researchers are investigating whether these changes contribute to long-COVID symptoms. This remains an active research area. At this point, stool microbiome testing is not a validated way to diagnose or treat long COVID.
Can Diet Prevent or Treat COVID Through the Gut?
A nutritious diet cannot replace medical prevention or treatment, but it can support overall immune function, recovery, and nutritional resilience. Adequate protein, fiber-rich plant foods, micronutrients, and hydration are all reasonable foundations during and after illness.
What Is Reasonable for Gut Health During or After Illness?
- Maintain adequate calories, protein, and fluids.
- Eat a varied diet with fruits, vegetables, legumes, whole grains, nuts, and seeds as tolerated.
- Use fermented foods if you enjoy and tolerate them.
- Avoid unnecessary restrictive diets during recovery.
- Discuss significant weight loss, persistent diarrhea, vomiting, or poor intake with a healthcare professional.
Do Probiotics Help?
Probiotics have been studied during COVID-19, but products vary widely and the evidence is not strong enough to recommend a general probiotic regimen for prevention or treatment. A strain or product used in one trial should not be generalized to all probiotics.
What About L-Glutamine, Collagen and Digestive Enzymes?
These supplements should not be presented as proven COVID or “gut-repair” treatments. They may have specific uses in selected clinical settings, but routine supplementation for COVID-related microbiome changes is not established.
When to Seek Care
Seek medical care for difficulty breathing, chest pain, confusion, severe dehydration, persistent high fever, or other concerning symptoms. If symptoms persist for weeks after infection, ask about evaluation for post-COVID conditions rather than assuming the microbiome is the sole cause.
For more general support with digestive symptoms, see our digestive and GI services.
References
- Yeoh YK, Zuo T, Lui GC-Y, et al. Gut microbiota composition reflects disease severity and dysfunctional immune responses in patients with COVID-19. Gut. 2021.
- A systematic review of gut microbiota profile in COVID-19 patients and among those who have recovered from COVID-19. 2023. PubMed.
- Gut Microbiome Dysbiosis in COVID-19: A Systematic Review and Meta-Analysis of Diversity Indices, Taxa Alterations, and Mortality Risk. 2025. PubMed.
