Conjugated linoleic acid improves insulin sensitivity in young, sedentary humans.
BACKGROUND
Preliminary evidence in obese diabetic rats suggests that conjugated linoleic acid (CLA) may have antidiabetic properties, based on reductions in fasting glucose and insulin concentrations. However, in lean rats, CLA causes hyperinsulinemia. Furthermore, experiments in humans also suggest that CLA may worsen insulin sensitivity.


OBJECTIVE
The present study examined whether CLA supplementation can improve insulin sensitivity in humans.


METHODS
: Sixteen young sedentary individuals (age, 21.5 +/- 0.4 yr (mean +/- SEM); body mass, 77.6 +/- 3.4 kg) participated in this study. Ten subjects received 4 g x d of mixed CLA isomers (35.5%cis-9, trans-11; 36.8%trans-10, cis-12) for 8 wk, whereas six subjects received placebo (safflower oil). Oral glucose tolerance tests were performed at baseline (0), 4 and 8 wk of supplementation.


RESULTS
: After 8 wk of CLA supplementation, insulin sensitivity index (ISI) increased (14.4 +/- 1.0, 8 wk vs 11.3 +/- 1.3, 0 wk; P < 0.05), which corresponded to a decrease in fasting insulin concentrations. Six of the 10 subjects showed large increases in their ISI (range, +27 to 90%), whereas two demonstrated essential no change (+3 to 5%), and two had a decrease in insulin sensitivity (-12 to -13%). ISI was unchanged over 8 wk in the placebo group.


CONCLUSIONS
Our results indicate that a common dosage of a commercially available CLA supplement can improve ISI in young, sedentary individuals. However, there is considerable individual variability in the response. Additional studies are required to identify underlying metabolic changes in human skeletal muscle.
Eyjolfson
Valerie
V
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
Spriet
Lawrence L
LL
Dyck
David J
DJ
D000328:Adult; D000704:Analysis of Variance; D000818:Animals; D019540:Area Under Curve; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance; D008041:Linoleic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011795:Surveys and Questionnaires
D008041:Linoleic Acids