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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Dietary Arachidonic Acid on Metabolism of Deuterated Linoleic Acid by Adult Male Subjects

Authors
item Emken, Edward
item Adlof, Richard
item Duval, Sandra
item Nelson, Gary

Submitted to: Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 1998
Publication Date: N/A

Interpretive Summary: Arachidonic acid is a fatty acid with many important biological functions and health effects. Fats in animal products and synthesis from vegetable fats are the two major sources of arachidonic acid in tissues. For many years, there has been speculation that arachidonic acid in animal fats is partly responsible for the negative health effects associated with meat products. The purpose of this research was to determine if dietary arachidonic acid has a health effect in adult human subjects and if production of arachidonic acid from linoleic acid is regulated. Results show that humans compensate for dietary intake of arachidonic acid by substantially reducing the amount synthesized by the body. The results show also that synthesis of arachidonic acid from linoleic acid is probably sufficient to meet adult daily requirements. This study did not find evidence that would suggest the amount of arachidonic acid in the U.S. diet has a major negative or positive health effect. These research findings are expected to impact the development of dietary guideline and will benefit both the consumer and producers of meat and egg products.

Technical Abstract: The influence of dietary supplementation with 20:4n-6 on uptake and turnover of deuterium-labeled linoleic acid (18:2n-6[d2]) in human plasma lipids and the synthesis of desaturated and elongated n-6 fatty acids from 18:2n-6[d2] was investigated in six adult male subjects. The subjects were fed either a high AA diet (HIAA) containing 1.7 g/d or a low AA diet (LOAA) containing 0.21 g/d of arachidonic acid for 50 days. Each subject was then dosed with 18:2n-6[d2] as the triglyceride. Nine blood samples were drawn over a 96 hr period. Plasma total lipid, triglyceride, phospholipid, and cholesterol ester were analyzed by GC-MS. Dietary 20:4n-6 supplementation did not affect uptake of 18:2n 6[d2] in plasma lipid classes over the 4-day study period nor the estimated half-life of 24-36 hr for 18:2n-6[d2]. The percentages of major deuterium-labeled desaturation and elongation products in plasma total lipid, as a % of total deuterated fatty acids, were 1.35% and 1.34% 18:3n-6[d2]; 0.53% and 0.50% 20:2n-6[d2]; 1.80% and 0.92% 20:3n-6[d2] and 3.13% and 1.51% 20:4n-6[d2] for the LOAA and HIAA diet groups respectively. Plasma total lipid concentration data for both 20:3n-6[d2] and 20:4n-6[d2] were 48% lower (p < 0.05) in samples from the HIAA diet group than in samples from the LOAA diet group. For a normal adult male consuming a typical US diet, the estimated total synthesis of 20:4n-6 from 20 g/d (68 mmole) of 18:2n-6 is 677 mg/d. Dietary supplementation with 1.5 g/d of 20:4n-6 reduced synthesis of 20:4n-6 from 20 g/d of 18:2n-6 to about 326 mg/d.

Last Modified: 7/30/2014
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