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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Dietary Docosahexaenoic Acid on Uptake and Desaturation of Isotope Labeled Oleic, Linoleic and Linolenic Acids by Male Subjects

item Emken, Edward - USDA, ARS, RETIRED
item Adlof, Richard
item Duval, Sandra
item Nelson, Gary

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: May 10, 1999
Publication Date: N/A

Technical Abstract: Six males were confined to a metabolic unit and fed diets containing 6 g/d (HIDHA) and 0.05 g/d (LODHA) 22:6n-3 for 90 days. At end of diet period, subjects were dosed with 2.95g 18:1n-9[d6], 2.34g 18:2n-6[d2], and 2.24g 18:3n-3[d4] (7.53g total) of deuterated triglycerides. Blood was drawn up to 72 hr. Chylomicron data showed that deuterated fatty acids were equally well absorbed and diet did not influence absorption. Dietary DHA enhanced chylomicron triglyceride clearance 25%. No diet effect was observed on acyltransferase selectivity or on uptake and clearance of 18:1n-9[d6], 18:2n-6[d2], and 18:3n-3[d4] into plasma lipids. DHA supplementation significantly reduced concentrations of n-6[d2] and n-3[d4] long-chain fatty acid (LCFA) metabolites in plasma lipids. Accumulation of 20:5n-3[d4] and 22:6n-3[d4] was depressed 76% and 88% respectively. Accumulation of 20:3n-6[d2] and 20:4n-6[d2] was decreased 72%. Results showed that feedback inhibition by 6 g/d DHA supplementation would reduce synthesis of n-3 LCFA metabolites from 2.5g 18:3n-3 in U.S. diets by about 90 mg/d. Synthesis of n-6 LCFA metabolites from 20g of 18:2n-6 in diets would be reduced by about 620 mg/d. Inhibition by DHA supplementation on accumulation of n-3 LCFA synthesized from 18:3n-3 is relatively unimportant since it represents a reduction of 1.5% of daily n-3 LCFA intake. Inhibition by DHA supplementation on accumulation of n-6 LCFA metabolites synthesized from 18:2n-6 is important since available n-6 LCFA would be reduced from 1000 mg/d to 380 mg/d. Results support hypothesis that benefits from DHA supplementation are related to reduced n-6 LCFA synthesis and increase in levels of dietary 22:6n-3 in tissue lipids.

Last Modified: 4/22/2015
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