Effect of a High Intake of Conjugated Linoleic Acid on Lipoprotein Levels in Healthy Human Subjects

Abstract

BackgroundTrans fatty acids are produced either by industrial hydrogenation or by biohydrogenation in the rumens of cows and sheep. Industrial trans fatty acids lower high-density lipoprotein (HDL) cholesterol, raise low-density lipoprotein (LDL) cholesterol, and increase the risk of coronary heart disease. The effects of trans fatty acids from ruminants are less clear. We investigated the effect on blood lipids of cis-9, trans-11 conjugated linoleic acid (CLA), a trans fatty acid largely restricted to ruminant fats.Methodology/Principal FindingsSixty-one healthy women and men were sequentially fed each of three diets for three weeks, in random order, for a total of nine weeks. Diets were identical except for 7% of energy (approximately 20 g/day), which was provided either by oleic acid, by industrial trans fatty acids, or by a mixture of 80% cis-9, trans-11 and 20% trans-10, cis-12 CLA. After the oleic acid diet, mean (± SD) serum LDL cholesterol was 2.68±0.62 mmol/L compared to 3.00±0.66 mmol/L after industrial trans fatty acids (p<0.001), and 2.92±0.70 mmol/L after CLA (p<0.001). Compared to oleic acid, HDL-cholesterol was 0.05±0.12 mmol/L lower after industrial trans fatty acids (p = 0.001) and 0.06±0.10 mmol/L lower after CLA (p<0.001). The total-to–HDL cholesterol ratio was 11.6% higher after industrial trans fatty acids (p<0.001) and 10.0% higher after CLA (p<0.001) relative to the oleic acid diet.Conclusions/SignificanceHigh intakes of an 80∶20 mixture of cis-9, trans-11 and trans-10, cis-12 CLA raise the total to HDL cholesterol ratio in healthy volunteers. The effect of CLA may be somewhat less than that of industrial trans fatty acids.Trial RegistrationClinicalTrials.gov NCT00529828

Association of foods enriched in conjugated linoleic acid (CLA) and CLA supplements with lipid profile in human studies: a systematic review and meta-analysis

“…Noone et al (23) observed that the daily intake of 3 g CLA supplement (50:50 and 80:20) decreased LDL-C levels non-significantly in CLA groups. However, von Loeffelholz (40) claimed that CLA supplementation for 6 months increased LDL-C and Desroches et al (2005) (27) Tricon et al (2006) (55) Wanders et al (2010) (34) Sofi et al (2010) (24) Raff et al (2008) (30) Chen et al (2012) (25) Naumann et The study-specific standardized difference (Std diff) in means and 95 % CI are represented by the black square and horizontal line, respectively; the area of the black square is proportional to the specific-study weight to the overall meta-analysis. The centre of the black diamond presents the pooled standardized difference in means and its width represents the pooled 95 % CI TC concentrations significantly.…”

“…(2010) (34) Sixty-one males and females, healthy normal weight (2012) (25) Eighty males and females, healthy overweight and obese…”

“…prevention of carcinogenesis, decrease body fat, enhancement of lean body mass, empowering the immune system and prevention of diabetes and CVD (14,15,21,(31)(32)(33) . However, the findings of human studies are controversial (17,25,26,30,34) . These differences may be related to the different forms and doses of CLA, study populations and duration of trials (25) .…”

The effect of conjugated linoleic acid, a natural trans fat from milk and meat, on human blood pressure: results from a randomized crossover feeding study

“…10 In this study we describe the effect of cis-9, trans-11 CLA on BP, which was a prespecified secondary end point of the study.…”

“…The samples were analysed for blood lipoproteins, as reported elsewhere. 10 Compliance to the diet was assessed by checking the diaries and by examining the fatty acid composition of cholesterylesters in plasma. The fatty acids in plasma cholesterylesters were analysed as described previously.…”