Effect of altered dietary n-3 fatty acid intake upon plasma lipid fatty acid composition, conversion of [13C]α-linolenic acid to longer-chain fatty acids and partitioning towards β-oxidation in older men

• Published in: British journal of nutrition Vol. 90; no. 2; pp. 311 - 321
• Main Authors: Burdge, Graham C., Finnegan, Yvonne E., Minihane, Anne M., Williams, Christine M., Wootton, Stephen A.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.08.2003
• Subjects: alpha-Linolenic Acid - administration & dosage; alpha-Linolenic Acid - metabolism; Biological and medical sciences; Carbon Dioxide - metabolism; Dietary Fats, Unsaturated - administration & dosage; Dietary Fats, Unsaturated - metabolism; Dietary n-3 polyunsaturated fatty acids; Docosahexaenoic Acids - administration & dosage; Docosahexaenoic Acids - metabolism; Eicosapentaenoic Acid - administration & dosage; Eicosapentaenoic Acid - metabolism; Fatty Acids - blood; Fatty Acids, Unsaturated - administration & dosage; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; Humans; Lipids - blood; Male; Man; Middle Aged; Oxidation-Reduction; Stable isotope; Vertebrates: anatomy and physiology, studies on body, several organs or systems; α-Linolenic acid; Dietary n-3 polyunsaturated fatty acids; Stable isotope; Man; α-Linolenic acid; Human; Long chain; Lipids; Male; Metabolism; n-3 fatty acid; α-Linolenic acid: Stable isotope: Dietary n-3 polyunsaturated fatty acids: Man; Feeding; Linolenic acid; Lipemia; Diet; β Oxidation; Unsaturated fatty acid; Macronutrient; Isotopes; Elderly
• ISSN: 0007-1145; 1475-2662
• DOI: 10.1079/BJN2003901

The effect of increased dietary intakes of α-linolenic acid (ALNA) or eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 2 months upon plasma lipid composition and capacity for conversion of ALNA to longer-chain metabolites was investigated in healthy men (52 (SD 12) years). After a 4-week baseline period when the subjects substituted a control spread, a test meal containing [U-13C]ALNA (700 mg) was consumed to measure conversion to EPA, docosapentaenoic acid (DPA) and DHA over 48 h. Subjects were then randomised to one of three groups for 8 weeks before repeating the tracer study: (1) continued on same intake (control, n 5); (2) increased ALNA intake (10 g/d, n 4); (3) increased EPA+DHA intake (1·5 g/d, n 5). At baseline, apparent fractional conversion of labelled ALNA was: EPA 2·80, DPA 1·20 and DHA 0·04 %. After 8 weeks on the control diet, plasma lipid composition and [13C]ALNA conversion remained unchanged compared with baseline. The high-ALNA diet resulted in raised plasma triacylglycerol-EPA and -DPA concentrations and phosphatidylcholine-EPA concentration, whilst [13C]ALNA conversion was similar to baseline. The high-(EPA+DHA) diet raised plasma phosphatidylcholine-EPA and -DHA concentrations, decreased [13C]ALNA conversion to EPA (2-fold) and DPA (4-fold), whilst [13C]ALNA conversion to DHA was unchanged. The dietary interventions did not alter partitioning of ALNA towards β-oxidation. The present results indicate ALNA conversion was down-regulated by increased product (EPA+DHA) availability, but was not up-regulated by increased substrate (ALNA) consumption. This suggests regulation of ALNA conversion may limit the influence of variations in dietary n-3 fatty acid intake on plasma lipid compositions.