Dietary α-linolenic acid improves skin blood flow following cold exposure and endothelial function in healthy adults: a randomized, double-blind, placebo-controlled, parallel-group comparative trial.

INTRODUCTION

Previous studies have suggested that α-linolenic acid (ALA) improves vascular function and alleviates allergic symptoms. However, its effects on cold sensitivity, associated with peripheral vascular function, remain poorly understood. Furthermore, no studies have reported ALA's efficacy alone in healthy humans regarding vascular endothelial function or allergic symptoms. This study aimed to clarify ALA intake effects on cold sensitivity, vascular endothelial function, and ocular/nasal allergy symptoms in healthy individuals.

METHODS

This randomized, double-blind, placebo-controlled, parallel-group trial enrolled 120 healthy Japanese adults experiencing cold sensitivity. Subjects consumed edible oils with different ALA contents (1.27 g or 2.03 g/day) or placebo for 12 weeks. Cold sensitivity (blood flow and skin temperature after cold exposure), vascular endothelial function, and allergy symptoms were measured.

RESULTS

Skin blood flow and skin surface temperature showed significantly higher values or trends toward higher values in ALA groups during early measurement period following cold exposure (p = 0.014 and 0.061, for skin surface temperature of the low- and high-dose groups, respectively). Overall flow-mediated dilation (FMD) analysis showed no significant differences between ALA groups (p = 0.128 and p = 0.412, for the low- and high-dose groups, respectively); however, subgroup analysis of subjects with pre-intervention values < 6% showed significant improvement (p = 0.038 and p = 0.043). No group differences were observed in allergy symptoms. Serum ALA concentrations were significantly higher in both ALA groups compared to the control group (p < 0.001). High-dose group showed, significantly higher serum EPA and DPA concentrations (p = 0.013 and p = 0.035, respectively).

CONCLUSION

ALA intake increased serum n-3 fatty acids and showed beneficial effects on cold sensitivity and endothelial function in Japanese adults without overt diseases.

CLINICAL TRIAL REGISTRATION: [https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000066500], identifier [UMIN000058298].