What do Cochrane systematic reviews say about probiotics as preventive interventions?

ABSTRACT BACKGROUND: Probiotics have been used for a range of clinical situations and their use is strongly encouraged by the media worldwide. This study identified and summarized all Cochrane systematic reviews about the preventive effects of probiotics in clinical practice. DESIGN AND SETTING: Review of systematic reviews, conducted in the Discipline of Evidence-Based Medicine, Escola Paulista de Medicina (EPM), Universidade Federal de São Paulo (Unifesp). METHODS: We included all Cochrane reviews on any probiotics when they were used as preventive interventions and compared with no intervention, placebo or any other pharmacological or non-pharmacological intervention. RESULTS: 17 Cochrane systematic reviews fulfilled our inclusion criteria and were summarized in this report. None of the reviews included in the present study provided high-quality evidence for any outcome. The benefits from use of probiotics included decreased incidence of antibiotic-associated diarrhea and Clostridium difficile-associated diarrhea; decreased incidence of upper respiratory tract infections and duration of episodes; decreased need for antibiotics and absences from school due to colds; and decreased incidence of ventilator-associated pneumonia. Probiotics seem to decrease the incidence of gestational diabetes mellitus, birthweight, risk of vaginal infection and incidence of eczema. CONCLUSION: Despite the marketing and the benefits associated with probiotics, there is little scientific evidence supporting the use of probiotics. None of the reviews provided any high-quality evidence for prevention of illnesses through use of probiotics. More trials are needed to gain better knowledge of probiotics and to confirm when their use is beneficial and cost-effective.

摘要 背景：益生菌（Probiotics）已被应用于多种临床场景，且受到全球各类媒体的大力推广。本研究对临床实践中涉及益生菌预防作用的全部科克伦（Cochrane）系统评价进行了识别与汇总。
研究设计与实施地点：本系统评价综述由圣保罗联邦大学（Universidade Federal de São Paulo, Unifesp）下属圣保罗医学院（Escola Paulista de Medicina, EPM）循证医学学科完成。
研究方法：本研究纳入所有将益生菌作为预防干预手段，并与无干预、安慰剂或其他任意药物/非药物干预措施进行对照的科克伦系统评价。
研究结果：共有17篇符合纳入标准的科克伦系统评价被纳入本报告并完成汇总。本次研究纳入的所有系统评价均未针对任意结局提供高质量证据。益生菌使用的获益包括：降低抗生素相关性腹泻与艰难梭菌相关性腹泻的发病率；缩短上呼吸道感染的发作时长并降低其发病率；减少因感冒所需的抗生素使用量及停课天数；降低呼吸机相关性肺炎的发病率。此外，益生菌或可降低妊娠期糖尿病发病率、阴道感染风险及湿疹发病率，并对新生儿出生体重产生影响。
研究结论：尽管益生菌存在市场推广行为且被认为具有多项获益，但目前仅有极少的科学证据支持其临床应用。本研究纳入的所有系统评价均未提供任何可证明益生菌可用于疾病预防的高质量证据。未来仍需开展更多临床试验，以深化对益生菌的认知，并明确其发挥获益作用的适用场景与成本效益。