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Effects of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of type 2 diabetes mellitus: a systematic review and meta‐analysis of randomised controlled trials
Author(s) -
Wang X.,
Tian J.,
Jiang J.,
Li L.,
Ying X.,
Tian H.,
Nie M.
Publication year - 2014
Publication title -
journal of human nutrition and dietetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.951
H-Index - 70
eISSN - 1365-277X
pISSN - 0952-3871
DOI - 10.1111/jhn.12181
Subject(s) - medicine , meta analysis , cochrane library , placebo , confidence interval , diabetes mellitus , insulin resistance , randomized controlled trial , type 2 diabetes mellitus , insulin , type 2 diabetes , relative risk , strictly standardized mean difference , green tea extract , traditional medicine , green tea , endocrinology , food science , alternative medicine , chemistry , pathology
Background Although the regular consumption of green tea or green tea extract has been considered to improve insulin sensitivity, the reported results are inconsistent. Therefore, we conducted a meta‐analysis to evaluate the effect of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of type 2 diabetes mellitus (T2 DM ). Methods Electronic databases, including P UBMED, The Cochrane Library, EMBASE , ISI Web of Knowledge, Chinese Biomedical Literature Database and Chinese Scientific Journals Fulltext Database, were systematically searched to identify randomised controlled trials ( RCT s) up to December 2011, supplemented by the Clinicaltrials.gov websites and the reference lists of identified studies. Two reviewers independently selected trials, extracted data, and evaluated the methodological qualities and evidence levels. Results Seven RCT s involving 510 participants were identified. There was no statistically significant difference between green tea or green tea extract group and placebo group with regard to fasting plasma glucose [standardised mean difference ( SMD ) 0.04; 95% confidence interval ( CI) −0.15 to 0.24], fasting serum insulin ( SMD −0.09; 95% CI −0.30 to 0.11), 2‐h plasma glucose in the oral glucose tolerance test ( OGTT −2 h) ( SMD −0.14; 95% CI −0.63 to 0.34), haemoglobin A 1 c ( SMD 0.10; 95% CI −0.13 to 0.33) and homeostasis model of insulin resistance ( HOMA IR ) index ( SMD −0.06; 95% CI −0.35 to 0.23) in participants at risk of T2 DM . Conclusions The consumption of green tea did not decrease the levels of fasting plasma glucose, fasting serum insulin, OGTT −2 h glucose, haemoglobin A 1 c and HOMA IR in populations at risk of T2 DM . Larger, longer‐term and high‐quality RCT s are needed to further definitely determine the effect of green tea or green tea extract on insulin sensitivity and glycaemic control in populations at risk of T2 DM .