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 .
Decreasing linoleic acid with constant alpha-linolenic acid in dietary fats increases (n-3) eicosapentaenoic acid in plasma phospholipids in healthy men.
High linoleic acid ( LA ) intakes have been suggested to reduce alpha-linolenic acid [ ALA , 18:3(n-3 ) ] metabolism to eicosapentaenoic acid [ EPA , 20:5(n-3 ) ] and docosahexaenoic acid [ DHA , 22:6(n-3 ) ] , and favor high arachidonic acid [ ARA , 20:4(n-6 ) ] . We used a r and omized cross-over study with men ( n = 22 ) to compare the effect of replacing vegetable oils high in LA with oils low in LA in foods , while maintaining constant ALA , for 4 wk each , on plasma ( n-3 ) fatty acids . Nonvegetable sources of fat , except fish and seafoods , were unrestricted . We determined plasma phospholipid fatty acids at wk 0 , 2 , 4 , 6 , and 8 , and triglycerides , cholesterol , serum CRP , and IL-6 , and platelet aggregation at wk 0 , 4 , and 8 .  LA and ALA intakes were 3.8 + /- 0.12 % and 1.0 + /- 0.05 % , and 10.5 + /- 0.53 % and 1.1 + /- 0.06 % energy with LA : ALA ratios of 4:0 and 10:1 during the low and high LA diets , respectively . The plasma phospholipid LA was higher and EPA was lower during the high than during the low LA diet period ( P < 0.001 ) , but DHA declined over the 8-wk period ( r = -0.425 , P < 0.001 ) . The plasma phospholipid ARA : EPA ratios were ( mean + /- SEM ) 20.7 + /- 1.52 and 12.9 + /- 1.01 after 4 wk consuming the high or low LA diets , respectively ( P < 0.001 ) ; LA was inversely associated with EPA ( r = -0.729 , P < 0.001 ) but positively associated with ARA : EPA ( r = 0.432 , P < 0.001 ) . LA intake did not influence ALA , ARA , DPA , DHA , or total , LDL or HDL cholesterol , CRP or IL-6 , or platelet aggregation . In conclusion , high LA intakes decrease plasma phospholipid EPA and increase the ARA : EPA ratio , but do not favor higher ARA
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 .