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 .
Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men.
BACKGROUND We recently showed that trans-10,cis-12 ( t10,c12 ) conjugated linoleic acid ( CLA ) causes insulin resistance in obese men . However , metabolic effects of the c9,t11 CLA isomer are still unknown in obese men . Because c9,t11 CLA is the predominant CLA isomer in foods and is included in dietary weight-loss products , it is important to conduct r and omized controlled studies that use c9,t11 CLA preparations . OBJECTIVE We investigated the effects of c9,t11 CLA supplementation on insulin sensitivity , body composition , and lipid peroxidation in a group at high risk for cardiovascular disease . DESIGN In a r and omized , double-blind , placebo-controlled study , 25 abdominally obese men received 3 g c9,t11 CLA/d or placebo ( olive oil ) . Before and after 3 mo of supplementation , we assessed insulin sensitivity ( hyperinsulinemic euglycemic clamp ) , lipid metabolism , body composition , and urinary 8-iso-prostagl and in F(2alpha ) ( a major F(2)-isoprostane ) and 15-keto-dihydro-prostagl and in F(2alpha ) , markers of in vivo oxidative stress and inflammation , respectively . RESULTS All subjects completed the study . Compared with placebo , c9,t11 CLA decreased insulin sensitivity by 15 % ( P < 0.05 ) and increased 8-iso-prostagl and in F(2alpha ) and 15-keto-dihydro-prostagl and in F(2alpha ) excretion by 50 % ( P < 0.01 ) and 15 % ( P < 0.05 ) , respectively . The decreased insulin sensitivity was independent of changes in serum lipids , glycemia , body mass index , and body fat but was abolished after adjustment for changes in 8-iso-prostagl and in F(2alpha ) concentrations . There were no differences between groups in body composition . CONCLUSIONS A CLA preparation containing the purified c9,t11 CLA isomer increased insulin resistance and lipid peroxidation compared with placebo in obese men . Because c9,t11 CLA occurs in commercial supplements as well as in the diet , the present results should be confirmed in larger studies that also include women
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 .