Effect of Conjugated Linoleic Acid as a Supplement or Enrichment in Foods on Blood Glucose and Waist Circumference in Humans: A Metaanalysis.
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 humans.


OBJECTIVE
The aim of this meta-analysis is to explore the effect of CLA on FBG and WC.


METHODS
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).


CONCLUSIONS
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.
Department of Nutrition, The Persian Gulf Tropical Medicine Research Center, Bushehr University of Medical Sciences, Bushehr. Iran.
Ali Reza
AR
Rahbar
Department of Epidemiology, The Persian Gulf Tropical Medicine Research Center, Bushehr University of Medical Sciences, Bushehr. Iran.
Afshin
A
Ostovar
Department of Nutrition, The Persian Gulf Tropical Medicine Research Center, Bushehr University of Medical Sciences, Bushehr. Iran.
Seyedeh-Masomeh
SM
Derakhshandeh-Rishehri
Department of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran. Iran.
Leila
L
Janani
Department of Endocrinology, The Persian Gulf Tropical Medicine Research Center, Bushehr University of Medical Sciences, Bushehr. Iran.
Amin
A
Rahbar
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects* / Q000378:metabolism; D019587:Dietary Supplements; D005527:Food, Fortified; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage*; D016032:Randomized Controlled Trials as Topic / Q000379:methods; D055105:Waist Circumference / Q000187:drug effects* / Q000502:physiology
D001786:Blood Glucose; D044243:Linoleic Acids, Conjugated
Conjugated linoleic acid; blood glucose; c10-conjugated linoleic acid; c9; meta-analysis; t11-conjugated linoleic acid; t12; waist
circumference