Effect of 1- and 2-Month High-Dose Alpha-Linolenic Acid Treatment on ¹³ C-Labeled Alpha-Linolenic Acid Incorporation and Conversion in Healthy Subjects

Scope: The study aims at identifying 1) the most sensitive compartment among plasma phospholipids, erythrocytes, and LDL for studying alpha-linolenic acid (ALA) conversion, and 2) whether ALA incorporation and conversion is saturable after administration of ¹³ C-labeled ALA-rich linseed oil (LO). The effect of a daily intake of 7 g nonlabeled LO (>43% w/w ALA) for 1 month after bolus administration of 7 g ¹³ C-labeled LO on day 1, and for 2 months after bolus administration of 7 g ¹³ C-labeled LO on day 1 and day 29 on ¹³ C-ALA incorporation and conversion into its higher homologs is investigated in healthy volunteers. Methods and results: Incorporation and conversion of LO-derived ¹³ C-labeled ALA is quantified by applying compartmental modeling. After bolus administration, a fractional conversion of approximately 30% from ¹³ C-ALA to ¹³ C-DHA is calculated as reflected by the LDL compartment. Treatment with LO for 8 weeks induces a mean reduction of ¹³ C-ALA conversion to ¹³ C-DHA by 48% as reflected by the LDL compartment, and a mean reduction of the ¹³ C-ALA incorporation into LDL by 46%. Conclusion: A 2-month dietary intake of a high dose of LO is sufficient to reach saturation of ALA incorporation into LDL particles, which are responsible for ALA distribution in the body.