The effects of kefir consumption on human health: a systematic review of randomized controlled trials

Context: Kefir, a traditional, fermented-milk beverage, has increasingly been promoted for various health benefits. The evidence from systematic reviews, however, is limited. 

Objective: Evidence from randomized controlled trials testing oral consumption of fermented-milk kefir on any outcome of human health or disease. 

Data Sources: A systematic search of 4 electronic databases (PubMed, Scopus, Allied and Complementary Medicine Database, and Cochrane Trials) from inception to July 31, 2021, was conducted. 

Data Extraction: Data extraction and risk-of-bias assessments were conducted by 2 reviewers independently. 

Data Analysis: A total of 18 publications reporting the results of 16 studies were included. Per the narrative analysis, fermented-milk kefir may have potential as a complementary therapy in reducing oral Streptococcus mutans, thereby reducing dental caries risk, and in Helicobacter pylori eradication therapy. Kefir may further aid treatment of adult dyslipidemia and hypertension, although evidence was very limited. Safety was only assessed in 5 of the 18 included publications, and 12 of the studies had an overall high risk for bias. 

Conclusion: Kefir is a dairy product with a unique microbiological profile that appears to be a safe for generally healthy populations to consume. However, efficacy and safety data from high-quality human trials are essential before any recommendations may be made for conditions of the oral and gastric microbiota and metabolic health.