Effect of Kefir Produced from Cow Milk on Clinical Outcomes and Immune Response of Patients with COVID-19: A Randomized Clinical Trial

Background: This study aimed to investigate the effect of kefir consumption, a popular traditional probiotic product, on the immune response and recovery of COVID-19 patients. Methods: In a double-blind, randomized controlled trial, 100 patients with COVID-19 were enrolled in two equal groups (receiving 250 cc of milk containing kefir granules (2 - 10%) twice daily for two weeks and a placebo group). Inflammatory indices, hematological factors, and clinical outcomes such as fever, pain, gastrointestinal symptoms, and dyspnea were assessed at the beginning and end of the study using a checklist prepared by the research team. Changes in parameters before and after the intervention were calculated. Results: We found that PO2 saturation, WBC, and neutrophil significantly increased in the placebo group, but Hb, lymphocyte, and platelet increased in the kefir-treated group. Also, CRP and ESR decreased in the kefir-treated group. The groups did not significantly differ in pulse rate, respiratory rate, and axillary temperature. There were no significant differences between the groups in signs and symptoms of the disease, except for the dry cough. Conclusions: Kefir seems to improve inflammatory factors slightly but does not significantly improve the disease symptoms.