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

Abstract

Objective: To compare the individual effects of dietary a-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 (À16%, Po0.001) and an increase in the maximum amount of conjugated dienes ( þ 7%, Po0.001). The EPA diet decreased the lag time (À16%, Po0.001) and the propagation rate (À12%, Po0.01). Tocopherol concentrations in LDL decreased in the ALA group (À13.5%, Po0.05) and DHA group (À7.3%, Po0.05). Plasma contents of tocopherol equivalents significantly decreased in all three experimental groups (ALA group: À5.0%, EPA group: À5.7%, DHA group: À12.8%). 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% (Po0.001), on the EPA diet the EPA content increased by 809% (Po0.001) and on the DHA diet, the DHA content increased by 200% (Po0.001). In addition, the EPA content also enhanced (without dietary intake) in the ALA group ( þ 35%, Po0.01) and in the DHA group ( þ 284%, Po0.001). 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. 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.

Daily Quercetin Supplementation Dose-Dependently Increases Plasma Quercetin Concentrations in Healthy Humans

“…Subjects were given a list of foods and beverages rich in quercetin (such as unpeeled apples, grape products, fruit juice, citrus fruits, berries, onions, broccoli, French beans, kale, tea, and red wine). Because dietary fatty acids, especially (n-3) fatty acids, and tocopherols affect antioxidant status and metabolic parameters (18,19), subjects were requested to exclusively use 1 particular commercial rapeseed oil and 1 margarine, respectively, which were rich in monounsaturated fatty acids. Other dietary sources of fatty acids and/or tocopherols such as nuts, seeds, and fatty fish were not permitted.…”

Effects of Dietary α-Linolenic Acid, Eicosapentaenoic Acid or Docosahexaenoic Acid on Parameters of Glucose Metabolism in Healthy Volunteers

“…The dietary regimens have been described in detail previously [25] . The diets consisted of conventional mixed foods.…”

“…As the basic study oil, we used a lowlinolenic rapeseed oil (3.7% ALA). For the three dietary groups, this oil was enriched either with ALA ethyl ester (ALA oil), EPA ethyl ester (EPA oil), or DHA ethyl ester (DHA oil) (for details see [25] ). The mean daily intake of ALA in the ALA group was 6.0 g, the mean daily intake of EPA in the EPA group was 2.8 g and the mean intake of DHA in the DHA group was 2.9 g. Body weight did not change significantly throughout the whole study.…”

“…This study was initially designed to examine the effects of the three n-3 PUFA on low-density lipoprotein composition and oxidizability [25] .…”

Margarines Fortified with α-Linolenic Acid, Eicosapentaenoic Acid, or Docosahexaenoic Acid Alter the Fatty Acid Composition of Erythrocytes but Do Not Affect the Antioxidant Status of Healthy Adults

“…We previously reported the individual effects of dietary ALA, EPA, and DHA on serum lipid profiles and LDL compositions (24,25). The present study was designed to compare the effects of dietary ALA, EPA, and DHA ethyl ester incorporated in a food matrix on the (n-3) fatty acid content of RBC over a 6-wk period in free-living, metabolically healthy volunteers.…”