A systematic review and meta-analysis: Vinegar consumption on glycaemic control in adults with type 2 diabetes mellitus.

AIM: To systematically review the effectiveness of vinegar consumption in improving glycaemic control in adults with type 2 diabetes mellitus.

DESIGN: A systematic review and meta-analysis.

REVIEW SOURCES: The CINAHL, Excerpta Medica database (EMBASE), Medline, PubMed, Scopus and Cochrane databases were searched in April 2019. Interventional studies published in the English language, from inception to 15 April 2019, were included.

REVIEW METHODS: Two investigators independently assessed the quality of the studies, discussed their findings to reach consensus and complied with the standards of the Cochrane Handbook for Systematic Reviews of Interventions. Random-effects meta-analysis was conducted in Review Manager 5.3.5 to assess the effect size. A series of subgroup and sensitivity analyses were conducted to explore the causes of heterogeneity. The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS: A total of six relevant studies, including 317 patients with type 2 diabetes mellitus, were selected from 356 studies identified through electronic searches and reference lists. The meta-analysis showed significantly better fasting blood glucose and haemoglobin A1c (HbA1c) level. In secondary analyses, there was a remarkable reduction in total cholesterol and low-density lipoprotein postintervention.

CONCLUSION: Vinegar content varied across the studies, and the sample sizes in the included studies were relatively small. Therefore, caution should be exercised when trying to extrapolate the results to a larger population.

IMPACT: Existing reviews are limited to narrative synthesis, lacking critical appraisal, heterogenous outcomes, nor any report of fasting blood glucose and HbA1c. This meta-analysis review extends the evidence on the beneficial effects of vinegar on glycaemic control as measured by HbA1c and fasting blood glucose. Clinicians could incorporate vinegar consumption as part of their dietary advice for patients with diabetes.