The effects of α-linolenic acid intake on skin and blood vessel health and subjective fatigue in middle-aged Japanese females: a randomized, double-blind, placebo-controlled, parallel-group comparative trial

α-linolenic acid (ALA) has antioxidant and anti-inflammatory effects. Previous studies have shown its effects on skin, blood vessels, and subjective fatigue; however, most were conducted in populations with low n-3 fatty acid intake. We investigated the effects of ALA on skin, vascular health, and subjective fatigue in the Japanese female population, which has a relatively high n-3 fatty acid intake. This randomized, placebo-controlled, double-blind, parallel trial enrolled 120 Japanese females aged 45-65 years. Participants ingested one of three edible oil blends (0.97 g, 1.36 g, or 2.13 g/day of ALA) or placebo for 12 weeks. Skin condition, vascular health and subjective fatigue were measured. Dietary effects were analyzed using statistical methods that accounted for multiplicity. No significant diet effect was observed for the primary outcome, TEWL (p = 0.428, 0.329). For exploratory outcomes, a significant diet effect was observed in skin hydration (p = 0.020). Intake of 2.13 g/day of ALA showed a trend toward higher change values than the control group at week 12 (p = 0.054). Brachial-ankle pulse wave velocity significantly decreased in all experimental oil groups compared to the control group (p = 0.008 ∼ 0.068). Serum n-3 fatty acid concentrations, particularly ALA, were significantly higher in all experimental groups than the control group (p = 0.0002 ∼ 0.035). No significant differences were observed between groups for subjective fatigue (VAS: smallest p = 0.102, POMS2: smallest p = 0.15). Even in the Japanese population, which on average consumes a high amount of n-3 fatty acids, it was shown that ALA intake can increase the concentration of n-3 fatty acids in blood serum and contribute to maintaining the health of blood vessels. In addition, in people of normal weight, ALA increased skin hydration and contributed to maintaining skin health.