The Mystery of Certain Strains in the Treatment of Gastrointestinal Symptoms of COVID-19: A Review.

COVID-19 presents a wide range of symptoms, including gastrointestinal manifestations such as diarrhea, nausea, and abdominal pain. has been proposed as a potential adjunct therapy to alleviate these symptoms due to its probiotic properties, which help restore gut microbiota balance and modulate immune responses. This review systematically analyzed studies assessing the effects of in COVID-19 patients with gastrointestinal symptoms. The literature search was conducted through PubMed and the WHO COVID-19 database using keywords such as "", "COVID-19", "gastrointestinal symptoms", and "inflammation markers". The search covered studies published until February 2025. Inclusion criteria: observational and clinical trials with for symptom relief. Exclusion: animal studies and non-ethical approvals. The findings suggest that supplementation may contribute to faster resolution of diarrhea, improved gut microbiota balance, and reduced inflammatory markers. However, some studies have found no significant impact on hospitalization rates or disease progression. The probiotic's mechanisms of action appear to involve microbiota modulation, intestinal barrier reinforcement, and anti-inflammatory effects rather than direct viral inhibition in COVID-19 after progression. Some strains show promise, and clinical validation should follow careful preclinical studies (in vitro, cell lines, and animal models), especially in vulnerable populations such as immunocompromised individuals. Understanding the gut-lung axis and its role in immune response regulation, together with the need for a thorough characterization of the specific strains, including biochemical, genomic, and functional properties, before testing in humans, may provide deeper insights into the therapeutic potential of probiotics in viral infections.