Serum α-linolenic acid, not intake, associates with reduced arterial stiffness assessed by brachial-ankle pulse wave velocity: an exploratory post hoc analysis of a randomized controlled trial

Introduction Our previous study showed that α -linolenic acid (ALA) intake was associated with a reduction in brachial-ankle pulse wave velocity (baPWV) in healthy middle-aged Japanese women. However, it remains unclear whether this effect depends on the ingested ALA itself or its metabolites. This study aimed to clarify two points: first, whether there is a relationship between ALA intake and serum n-3 fatty acid concentrations; and second, whether ALA intake or serum concentrations of n-3/n-6 fatty acids are related to the previously reported effect of ALA on maintaining vascular flexibility. Methods We conducted a post hoc analysis of a previously reported randomized controlled trial. Correlation analyses assessed the relationships between ALA intake and serum n-3 fatty acids. Associations of baPWV with n-3/n-6 fatty acid intake and serum concentrations were tested using an analysis of covariance-type linear model. Results No significant correlation was found between ALA intake and serum n-3 fatty acid concentrations. Serum ALA correlated positively with serum docosapentaenoic acid (DPA) ( p < 0.001, r = 0.444), docosahexaenoic acid (DHA) ( p = 0.006, r = 0.292), and the sum of serum eicosapentaenoic acid, DPA, and DHA ( p = 0.009, r = 0.275). ALA intake was not associated with baPWV, whereas serum ALA showed a significant negative association with baPWV ( p = 0.027, regression coefficient: −2.45); serum arachidonic acid showed a significant positive association ( p = 0.047, regression coefficient: 1.11). No associations were observed for other n-3/n-6 fatty acids. Discussion This study suggests substantial inter-individual variation in the relationship between ALA intake and serum ALA concentration. Furthermore, it suggests that serum ALA concentration, rather than ALA intake, may be more closely associated with vascular stiffness, as assessed by baPWV. Clinical trial registration https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000060078 , identifier UMIN000052677.