There was a significant heterogeneity for the impact of CLA  on CRP and IL-6 , but not TNF-α .
Conclusions This meta- analysis showed that CLA supplementation may increase inflammatory markers ( CRP and TNF-α ) .
Background / objectives Conjugated linoleic acid ( CLA ) is a polyunsaturated fatty acid with attractive biological activities .
Numerous studies have been conducted on the inflammation-lowering effects of CLA in in vitro and animal models .
However , the effects of CLA treatment on the inflammatory markers in humans are controversial .
Supplementation With Conjugated Linoleic Acid Causes Isomer-Dependent Oxidative Stress and Elevated C-Reactive Protein: A Potential Link to Fatty Acid-Induced Insulin Resistance
Background —Conjugated linoleic acids ( CLAs ) , a group of fatty acids shown to have beneficial effects in animals , are also used as weight loss supplements . Recently , we reported that the t 10 c 12 CLA-isomer caused insulin resistance in abdominally obese men via unknown mechanisms . The aim of the present study was to examine whether CLA has isomer-specific effects on oxidative stress or inflammatory biomarkers and to investigate the relationship between these factors and induced insulin resistance . Methods and Results —In a double-blind placebo-controlled trial , 60 men with metabolic syndrome were r and omized to one of 3 groups receiving t 10 c 12 CLA , a CLA mixture , or placebo for 12 weeks . Insulin sensitivity ( euglycemic clamp ) , serum lipids , in vivo lipid peroxidation ( determined as urinary 8-iso-PGF2&agr ; [ F2-isoprostanes ] ) , 15-ketodihydro PGF2&agr ; , plasma vitamin E , plasma C-reactive protein , tumor necrosis factor-&agr ; , and interleukin-6 were assessed before and after treatment . Supplementation with t 10 c 12 CLA markedly increased 8-iso-PGF2&agr ; ( 578 % ) and C-reactive protein ( 110 % ) compared with placebo ( P < 0.0001 and P < 0.01 , respectively ) and independent of changes in hyperglycemia or dyslipidemia . The increases in 8-iso-PGF2&agr ; , but not in C-reactive protein , were significantly and independently related to aggravated insulin resistance . Oxidative stress was related to increased vitamin E levels , suggesting a compensatory mechanism . Conclusions —t 10 c 12 CLA supplementation increases oxidative stress and inflammatory biomarkers in obese men . The oxidative stress seems closely related to induced insulin resistance , suggesting a link between the fatty acid-induced lipid peroxidation seen in the present study and insulin resistance . These unfavorable effects of t 10 c 12 CLA might be of clinical importance with regard to cardiovascular disease , in consideration of the widespread use of dietary supplements containing this fatty acid
There was a significant heterogeneity for the impact of CLA  on CRP and IL-6 , but not TNF-α .
Conclusions This meta- analysis showed that CLA supplementation may increase inflammatory markers ( CRP and TNF-α ) .
Background / objectives Conjugated linoleic acid ( CLA ) is a polyunsaturated fatty acid with attractive biological activities .
Numerous studies have been conducted on the inflammation-lowering effects of CLA in in vitro and animal models .
However , the effects of CLA treatment on the inflammatory markers in humans are controversial .