Effect of Conjugated Linoleic Acid as a Supplement or Enrichment in Foods on Blood Glucose and Waist Circumference in Humans: A Metaanalysis
Ali Reza Rahbar,
Background: Controversy persists regarding the effect of mixtures of conjugated linoleic
acids (c9, t11- and t10, c12-CLA) in fasting blood glucose (FBG) and waist circumference (WC) in
Objective: The aim of this meta-analysis is to explore the effect of CLA on FBG and WC.
Method: PubMed, Google Scholar, Cochrane Library, Science Direct, Pro-Quest and Ovid were
searched up to January 2015. Studies that examined the effect of CLA supplementation or foods
enriched with CLA on FBG and WC in healthy adults were included. Studies in animals or unhealthy
individuals and studies other than clinical trials were excluded. Of the 3,095 articles initially
retrieved, 32 eligible randomized clinical trials were included in this systematic review. The mean
difference and standard deviation of changes in FBG and WC in the intervention and control groups
were used as effect size measures for the meta-analysis.
Results: Subgroup analysis showed that CLA supplement consumption did not significantly influence
FBG (standardized mean differences [SMD] = 0.075 mg/dL; 95% confidence interval (CI) = −0.099
to 0.249; p = 0.399) or WC (SMD = -0.149 cm; 95% CI = −0.522 to 0.225; p = 0.435). Foods
enriched in CLA also showed no significant effect on FBG (SMD = 0.126 mg/dL; 95% CI = −0.100
to 0.352; p = 0.274) or WC (SMD = -0.233 cm; 95% CI = −0.625 to 0.159; p = 0.244).
Conclusion: We conclude that c9, t11- and t10, c12-CLA administered as a supplement or used to
enrich foods does not affect FBG or WC in humans.
Keywords: Conjugated linoleic acid, t12, c10-conjugated linoleic acid, c9, t11-conjugated linoleic acid, blood glucose, waist
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