Conjugated Linoleic Acid Often Has Mixed Effects in Type 2 Diabetes CME
News Author: Laurie Barclay, MD
CME Author: Charles Vega, MD, FAAFP



Oct. 1, 2004 — Supplementation with conjugated linoleic acid (CLA) has mixed effects in type 2 diabetes mellitus, according to the results of a randomized, double-blind trial published in the October issue of the American Journal of Clinical Nutrition. CLA had an adverse effect on insulin and glucose metabolism while having a beneficial effect on lipids.

"Some animal studies have suggested that CLA supplementation may have therapeutic potential with respect to insulin sensitivity and lipid metabolism, which are important cardiovascular disease (CVD) risk factors associated with type 2 diabetes mellitus," write Fiona Moloney, MD, from the Trinity Centre for Health Sciences in Dublin, Ireland, and colleagues. "There are relatively few human intervention studies, and the results of those few are mixed. Most of the evidence regarding body composition suggests that CLA supplementation does not reduce body weight or body fat or increase fat-free mass in humans."

In this study, 32 subjects with stable, diet-controlled type 2 diabetes received CLA (3.0 g/day; 50:50 blend of cis-9,trans-11 CLA and trans-10,cis-12 CLA) or placebo for eight weeks. Before and after the intervention, subjects had a three-hour 75-g oral glucose-tolerance test, and measurement of fasting plasma lipid concentrations and inflammatory markers.

CLA supplementation increased fasting glucose concentrations by 6.3% (P < .05), and it reduced insulin sensitivity measured by homeostasis model assessment, oral glucose insulin sensitivity, and the insulin sensitivity index (composite; P < .05).

Because of an increase in high-density lipoprotein2 (HDL2 ) cholesterol concentrations in the CLA group (P < .05), total HDL-cholesterol concentrations increased by 8% (P < .05), and the ratio of low-density lipoprotein (LDL) to HDL cholesterol decreased (P < .01). CLA supplementation also reduced fibrinogen concentrations (P < .01) but had no effect on CVD inflammatory markers (C-reactive protein and interleukin 6).

"CLA supplementation had an adverse effect on insulin and glucose metabolism," the authors write. "Whereas CLA had positive effects on HDL metabolism and fibrinogen, a therapeutic nutrient should not be associated with potentially adverse effects on other clinical markers of type 2 diabetes.... Clearly the effect of CLA supplementation is isomer-specific and dependent on the diabetic risk of the experimental model."

The Wellcome Trust, U.K., supported one of the authors. None of the authors have any commercial interest in CLA or any other conflict of interest.

Am J Clin Nutr. 2004;80:887-895

http://www.medscape.com/viewarticle/490444