Abstract

Keywords

The occurrence of trans-18:1 isomers in plasma lipids classes in humans

MP Mansour^1,2, D Li³ & AJ Sinclair³

Correspondence to: AJ Sinclair, Department of Food Science, RMIT University, GPO Box 2476V, Melbourne, VIC 3001, Australia.
Email: andrew.sinclair@rmit.edu.au

Guarantor: Professor Andrew Sinclair.
Contributors: AJS and MPM initiated the study. MPM did laboratory assays and collected data. AJS selected the study site, supervised the project, and secured the funding. DL prepared the draft of paper and did the statistical analysis. All investigators contributed to the drafts of paper

Objective: The aim of this study was to examine the distribution of trans fatty acids (TFA) in plasma lipid classes and the relationship with dietary intake of TFA.

Design: After a 2 week baseline (habitual) diet, all subjects consumed a moderate fat (MF) diet for 3 weeks with the fat being derived mainly from margarine and the rest from lean beef, and then a very low fat (VLF) diet for 3 weeks with the TFA being derived only from the lean beef. Blood samples were collected 2 days prior to the end and also on the last day of each dietary period.

Setting: Deakin Institute of Human Nutrition, Deakin University, Geelong, Australia.

Subjects: Ten free-living mildly hypercholesterolaemic subjects aged 22–66 were recruited in Geelong.

Outcome measures: TFA intake was calculated from analyses of Australian margarines, butter, lean meat and animal fat. The TFA in plasma lipid fractions were separated by AgNO₃ thin-layer chromatography and quantitated by capillary gas–liquid chromatography using internal standards.

Results: The phospholipid (PL) fraction contained more than 60% of the trans-18:1 isomers in the plasma lipids in all subjects. On the baseline diet, the predominant positional isomer of trans-18:1 in PL was 11, whereas in the other lipid classes it was the 9 isomer. The concentration of the 9 isomer increased on the MF diet, particularly in the PL fraction, while the concentration of the 11 isomer decreased in all fractions. On the VLF diet, the total TFA level decreased by approximately 50%, mainly due to decreases in the TFA isomers in the PL and TG fractions. Changes in plasma total and PL TFA, PL 9, 10 and 11 were strongly correlated with dietary TFA intake (P<0.0001). There were also significant association between dietary TFA intake and PL 12 (P=0.003), triacylglycerol 9 (P=0.009), 11 (P=0.0005), total triacylglycerol (P=0.023) and free fatty acid TFA (P=0.042).

Conclusions: The results suggest that the measurement of trans-18:1 in plasma PL and TAG, and plasma total TFA could be used to estimate the intake of TFA.

Sponsorship: Meat Research Corporation of Australia.

European Journal of Clinical Nutrition (2001) 55, 59–64

^© Macmillan Publishers Ltd 2001