Verspäteter Nachtrag zum Thema CLA:

Med Sci Sports Exerc. 2004 May;36(5):814-20.

Conjugated linoleic acid improves insulin sensitivity in young, sedentary humans.

Eyjolfson V, Spriet LL, Dyck DJ.

Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.

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. OBJECTIVES: The present study examined whether CLA supplementation can improve insulin sensitivity in humans. DESIGN:: 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.
Martha Belury (Dietary conjugated linoleic acid in health: physiological effects and mechanisms of action. In: Annu. Rev. Nutr. 2002. 22:505–31) über CLA:
Thus far, studies using supplements in humans have shown that supplementation with CLA for short periods of time (up to 12 weeks), reduces body weight and body fat in some studies (15, 101, 105). However, at least one study has found that supplementation with CLA results in elevated levels of the lipid peroxidation product, 15-keto-dihydro-prostaglandin-F2Æ, in urine (5). Understanding the role of CLA in modulating events associated with macronutrient metabolism suggests
that CLA may be a healthy dietary component with the potential for impacting human health in the areas of cancer, obesity, diabetes, and cardiovascular disease.
However, more work is needed to fully elucidate the safety and efficacy of isomers and doses that are required for exerting this breadth of potential beneficial effects.
In der Nurses` Health Study zeigte sich zwar ein deutlicher Zusammenhang zwischen synthetisch erzeugten Transfettsäuren und KHK-Risiko. Die Aufnahme von natürlichen Transfettsäuren aus tierischen Produkten (Milchprodukte, Rindfleisch...) schien das Risiko für Herz-Kreislauferkrankungen dagegen nicht zu erhöhen. (Vgl.: Willett et al.: Intake of trans fatty acids and risk of coronary heart disease among women. In: Lancet. 1993 Mar 6;341(8845):581-5.)
Stender und Dyerberg (Influence of Trans Fatty Acids on Health. In: Ann Nutr Metab 2004;48:61–66) kommen zu dem Schluss, dass Transfettsäuren aus Fleisch und Milchprodukten - selbst wenn man von einem ähnlichen Gefährdungspotential ausgeht - wegen ihres geringen Vorkommens nur ein geringes Gesundheitsproblem darstellen.

Gruß