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Association of conjugated linoleic acid consumption and liver enzymes in human studies: A systematic review and meta-analysis of randomized controlled clinical trials

Mirzaii, Safiye, Mansourian, Marjan, Derakhshandeh-Rishehri, Seyedeh-Masomeh, Kelishadi, Roya, Heidari-Beni, Motahar
Nutrition 2016 v.32 no.2 pp. 166-173
adults, alanine transaminase, alkaline phosphatase, aspartate transaminase, blood serum, confidence interval, conjugated linoleic acid, foods, liver, meta-analysis, prospective studies, randomized clinical trials, systematic review
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.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.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.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.