Original Article

European Journal of Clinical Nutrition (2007) 61, 314–325. doi:10.1038/sj.ejcn.1602523; published online 13 September 2006

Influence of three rapeseed oil-rich diets, fortified with alpha-linolenic acid, eicosapentaenoic acid or docosahexaenoic acid on the composition and oxidizability of low-density lipoproteins: results of a controlled study in healthy volunteers

Guarantor: S Egert.

Contributors: SE participated in designing and planning the study, calculated the diets, headed the investigation during the dietary period, measured the parameters of LDL oxidizability, performed the statistical analysis and wrote the paper together with UW, who also contributed to designing and planning of the study. FK measured LDL fatty acid composition, MF measured LDL tocopherol levels and KK measured plasma tocopherol levels. UW initiated the project together with VS and HFE.

S Egert1, V Somoza2, F Kannenberg3,4, M Fobker4, K Krome2, H F Erbersdobler5 and U Wahrburg1

  1. 1Department of Human Nutrition, University of Applied Sciences, Muenster, Germany
  2. 2German Research Center of Food Chemistry, Garching, Germany
  3. 3Leibniz-Institute of Arteriosclerosis Research at the University of Muenster, Muenster, Germany
  4. 4Institute of Clinical Chemistry and Laboratory Medicine, University of Muenster, Muenster, Germany
  5. 5Institute of Human Nutrition and Food Science, University of Kiel, Kiel, Germany

Correspondence: Dr S Egert, Department of Human Nutrition, University of Applied Sciences, Corrensstrasse 25, 48149 Muenster, Germany. E-mail: segert@fh-muenster.de

Received 16 November 2005; Revised 8 June 2006; Accepted 4 July 2006; Published online 13 September 2006.

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Abstract

Objective:

 

To compare the individual effects of dietary alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) on low-density lipoprotein (LDL) fatty acid composition, ex vivo LDL oxidizability and tocopherol requirement.

Design, setting and subjects:

 

A randomized strictly controlled dietary study with three dietary groups and a parallel design, consisting of two consecutive periods. Sixty-one healthy young volunteers, students at a nearby college, were included. Forty-eight subjects (13 males, 35 females) completed the study.

Interventions:

 

Subjects received a 2-week wash-in diet rich in monounsaturated fatty acids (21% energy) followed by experimental diets enriched with about 1% of energy of ALA, EPA or DHA for 3 weeks. The omega-3 (n-3) fatty acids were provided with special rapeseed oils and margarines. The wash-in diet and the experimental diets were identical, apart from the n-3 fatty acid composition and the tocopherol content, which was adjusted to the content of dienoic acid equivalents.

Results:

 

Ex vivo oxidative susceptibility of LDL was highest after the DHA diet, indicated by a decrease in lag time (-16%, P<0.001) and an increase in the maximum amount of conjugated dienes (+7%, P<0.001). The EPA diet decreased the lag time (-16%, P<0.001) and the propagation rate (-12%, P<0.01). Tocopherol concentrations in LDL decreased in the ALA group (-13.5%, P<0.05) and DHA group (-7.3%, P<0.05). Plasma contents of tocopherol equivalents significantly decreased in all three experimental groups (ALA group: -5.0%, EPA group: -5.7%, DHA group: -12.8%). The content of the three n-3 polyunsaturated fatty acid differently increased in the LDL: on the ALA diet, the ALA content increased by 89% (P<0.001), on the EPA diet the EPA content increased by 809% (P<0.001) and on the DHA diet, the DHA content increased by 200% (P<0.001). In addition, the EPA content also enhanced (without dietary intake) in the ALA group (+35%, P<0.01) and in the DHA group (+284%, P<0.001).

Conclusions:

 

Dietary intake of ALA, EPA or DHA led to a significant enrichment of the respective fatty acid in the LDL particles, with dietary EPA preferentially incorporated. In the context of a monounsaturated fatty acid-rich diet, ALA enrichment did not enhance LDL oxidizability, whereas the effects of EPA and DHA on ex vivo LDL oxidation were inconsistent, possibly in part due to further changes in LDL fatty acid composition.

Sponsorship:

 

This research was financially supported by the German Federal Ministry of Education and Research (BMBF) within the project 'NAPUS 2000 – healthy foodstuffs from transgenic rapeseed'.

Keywords:

omega-3 fatty acids, rapeseed oil, dietary study, LDL oxidation

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