title: Association of conjugated linoleic acid consumption and liver enzymes in human studies: A systematic review and meta-analysis of randomized controlled clinical trials.
abstract: OBJECTIVE
  The aim of this study was to systematically review the association of conjugated linoleic acid (CLA) consumption in two forms of foods enriched or supplemented with CLA on serum liver enzymes in human studies.
  
  
  METHODS
  We searched PubMed, Google Scholar, Cochrane Library, ScienceDirect, ProQuest, and Ovid up to January 2015. Studies that examined the effect of CLA supplementation or foods enriched with CLA on liver enzymes concentrations among healthy adults were included. The mean difference and SD of changes in serum liver enzymes between the intervention and control groups were used as effect size for the meta-analysis.
  
  
  RESULTS
  The analysis demonstrated that CLA supplementation led to slight and nonsignificant decreases in alkaline phosphatase (ALP) levels (mean difference [MD] -0.216; 95% confidence interval [CI], -0.60 to 0.17; P = 0.28). CLA intake can nonsignificantly increase alanine transaminase (ALT) levels (MD = 0.107 U/L; 95% CI, -0.29 to 0.244; P = 0.124) and can significantly increase aspartate aminotransferase (AST) levels (MD = 0.171 U/L; 95% CI, 0.034-0.307; P = 0.01). Subgroup analysis based on CLA source showed that CLA supplementation or foods enriched with CLA did not significantly alter ALT levels. Subgroup analysis showed that CLA supplementation led to significant increases in AST levels (MD = 0.224 U/L; 95% CI, 0.071-0.376; P = 0.004). However, foods enriched with CLA did not have any significant effects on AST levels.
  
  
  CONCLUSIONS
  CLA supplementation was associated with a significantly increased circulating AST without any significant effect on ALP and ALT levels. Prospective studies are necessary to assess the clinical outcomes of the association between CLA and liver enzyme concentrations.
authors.affiliation: Food Security Research Center, Department of Clinical Nutrition, School of Nutrition & Food Sciences, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Safiye
authors.initials: S
authors.lastname: Mirzaii
authors.affiliation: Department of Biostatistics and Epidemiology, School of Health, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Marjan
authors.initials: M
authors.lastname: Mansourian
authors.affiliation: Food Security Research Center, Department of Clinical Nutrition, School of Nutrition & Food Sciences, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Seyedeh-Masomeh
authors.initials: SM
authors.lastname: Derakhshandeh-Rishehri
authors.affiliation: Child Growth and Development Research Center, Research Institute for Primordial Prevention of Non-communicable Disease, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Roya
authors.initials: R
authors.lastname: Kelishadi
authors.affiliation: Food Security Research Center, Department of Community Nutrition, School of Nutrition & Food Sciences, Isfahan University of Medical Sciences, Isfahan, Iran. Electronic address: motahar.heidari@nutr.mui.ac.ir.
authors.forename: Motahar
authors.initials: M
authors.lastname: Heidari-Beni
mesh_terms: D000410:Alanine Transaminase / Q000097:blood; D000469:Alkaline Phosphatase / Q000097:blood; D001219:Aspartate Aminotransferases / Q000097:blood; D016208:Databases, Factual; D019587:Dietary Supplements; D005527:Food, Fortified; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage*; D008099:Liver / Q000187:drug effects* / Q000201:enzymology*; D016032:Randomized Controlled Trials as Topic
chemical_list: D044243:Linoleic Acids, Conjugated; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000469:Alkaline Phosphatase
keywords: Alanine aminotransferase; Alkaline phosphatase; Aspartate aminotransferase; Conjugated linoleic acid; Meta-analysis; Systematic review