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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2006;26:307.)
© 2006 American Heart Association, Inc.

Vascular Biology

Conjugated Linoleic Acid Impairs Endothelial Function

Justin S.W. Taylor; Simon R.P. Williams; Rhian Rhys; Phillip James; Michael P. Frenneaux

From Morriston Hospital, Swansea, UK; University of Glamorgan, Pontypridd, UK; Royal Glamorgan Hospital, Llantrisant, UK; Wales Heart Research Institute, Cardiff, UK; Dept Cardiovascular Medicine, The University of Birmingham, Birmingham, UK.

Correspondence to Justin S. W. Taylor, Department of Cardiology, Morriston Hospital, Morriston, Swansea SA6 6NL, UK. E-mail jswt{at}totalise.co.uk

Objectives— To determine the effect of dietary supplementation with conjugated linoleic acid (CLA) on body mass index (BMI), body fat distribution, endothelial function, and markers of cardiovascular risk.

Methods and Results— Forty healthy volunteers with BMI >27 kg/m² were randomized to receive a CLA isomeric mixture or olive oil in a 12-week double-blind study. Subcutaneous body fat and abdominal/hepatic fat content were assessed using skin-fold thicknesses and computed tomography scanning, respectively. Endothelial function was assessed by brachial artery flow-mediated dilatation (FMD). Plasma isoprostanes were measured as an index of oxidative stress. CLA supplementation did not result in a significant change in BMI index or total body fat. There was a significant decrease in limb (–7.8 mm, P<0.001), but not torso skin-fold thicknesses or abdominal or liver fat content. Brachial artery FMD declined (–1.3%, P=0.013), and plasma F2-isoprostanes increased (+91pg/mL, P=0.042).

Conclusions— A CLA isomeric mixture had at most modest effects on adiposity and worsened endothelial function. On the basis of these results, the use of the isomeric mixture of CLA as an aid to weight loss cannot be recommended.

Twelve-week supplementation with isomeric conjugated linoleic acid (CLA) did not change BMI or total body fat compared with olive oil. There was a decrease in limb, but not torso skin fold thicknesses, a decrease in FMD of the brachial artery, and an increase in plasma F2-isoprostanes. Isomeric CLA cannot be recommended as a dietary supplement to aid weight loss.

Key Words: body composition • conjugated linoleic acid • endothelial function • obesity • oxidative stress

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