Conversion of α-linolenic acid to palmitic, palmitoleic, stearic and oleic acids in men and women

The purpose of this study was to determine whether adult humans can recycle carbon from alpha-linolenic acid (18:3n-3) into saturated (SFA) and monounsaturated (MUFA) fatty acids. Six men and six women consumed 700 mg [U-C-13]-18:3n-3. Blood was collected over 21 days and breath over 24 h. [C-13]-labelled SFA and MUFA were detected in plasma phosphatidylcholine (PC) and triacylglycerol (TAG). Total labelled fatty acid incorporation into SFA and MUFA was five- and 25-fold greater in PC than TAG in men and women, respectively. [C-13]-16:0 was the major labelled fatty acid in both fractions. Total [C-13] incorporation into SFA and MUFA was 20% greater in men than women, and related positively (r(2) = 0.35, P < 0.05) to the fractional recovery of labelled 18:3n-3 as (CO2)-C-13 on breath. These results suggest that the extent of partitioning towards beta-oxidation and carbon recycling may regulate the availability of 18:3n-3 for conversion to longer-chain fatty acids. (C) 2003 Elsevier Ltd. All rights reserved.