The effect of dietary trans alpha-linolenic acid on plasma lipids and platelet fatty acid composition: the TransLinE study

Objective: To collect (i) baseline data and (ii) execute a large multicentr e study examining the effect of trans alpha-linolenic acid on its incorpora tion into plasma lipids and on risk factors for coronary heart disease. Design: Male volunteers were recruited and the habitual diet assessed by a 4-d weighed record. Fatty acid composition of plasma and platelet lipids we re determined by gas chromatography at baseline. After a 6 week run-in peri od on a trans 'free' diet, male volunteers were randomised to consume 0.6% of energy trans alpha-linolenic acid or to continue with a diet 'low' in tr ans alpha-linolenic acid for 6 weeks. Setting: Three European university research departments supported by the re search and development departments of the food industry. Subjects: Male volunteers (88) recruited by local advertisement. Methods: Replacement of 30% of the fat of the habitual diet by margarine, o il and foods. Rapeseed oil was deodorised especially to produce the trans ' free' and 'high' trans foods for this study. The incorporation and conversi on of trans alpha-linolenic acid into plasma lipids and platelets was asses sed by gas chromatography and dietary compliance was verified by 4-d weighe d record. Results Less trans alpha-linolenic acid isomers are incorporated into human plasma lipids in French volunteers than in Dutch or Scottish volunteers co nsuming their habitual diets. Trans 'free' alpha-linolenic acid-rich oil ca n be produced by careful deodorization during refining. The 'high' trans di et provided 1410 +/- 42 mg/d trans isomers of alpha-linolenic acid, whilst the 'low' trans group consumed 60 +/- 75 mg/d. The change in plasma lipid a nd platelet fatty acid composition documented that trans linolenic isomers are incorporated and converted to a trans isomer of eicosapentaenoic acid. Only the 15-trans alpha-linolenic acid is incorporated into plasma choleste ryl esters. The group consuming low trans diet had a slightly higher intake of fat, especially saturated and monounsaturated fat. Conclusions: Trans 'free' rapeseed oil, rich in alpha-linolenic acid, can b e produced by careful deodorization. Dietary records show good compliance. Dietary trans isomers of alpha-linolenic acid are incorporated in plasma li pids and converted to long-chain polyunsaturated fatty acids. Their effects on risk factors for coronary heart disease and their metabolism will be re ported elsewhere.