5—アミノレブリン酸含有食品の老化皮膚性状に及ぼす効果―無作為化二重盲検プラセボ対照並行群間比較試験―

Objective The aim of the present study was to evaluate dermal effects of daily 5-aminolevulinic acid（ALA）supplementation. Methods The study was a 12-week randomized, double-blind, placebo-controlled trial on women aged 45-64 years complaining of skin dryness. Forty-five participants were randomly assigned to receive ALA︱free placebo, low-dose ALA supplement（25 mg╱day of ALA phosphate）, or high-dose ALA supplement（50 mg╱day of ALA phosphate）daily for 12 weeks. We evaluated the skin collagen density and the stratum corneum hydration（SCH）on the cheek and the volar forearm using an ultrasound apparatus（DermaLab(R)）and a Corneometer(R), respectively. Results Analyses of the total evaluable population revealed that low-dose and╱or high-dose ALA intakes were likely to increase the collagen density on the cheek, particularly after 8 weeks on women taking the high-dose ALA compared to the baseline levels（P＜0.05）, whereas these ALA intakes had no significant effects on the SCH either on the cheek or on the volar forearm throughout the intervention. However, in the ad hoc subgroup analysis, there was a trend for high-dose ALA intakes to increase the SCH in the older subpopulation（55-64 years）. We observed a more promising change（P＝0.061）in the SCH on the volar forearm after 12 weeks of treatment. ALA at both doses was well tolerated, without any reported untoward side effects. Conclusion Although our results are not final, they suggest that ALA supplement may increase the dermal collagen density in healthy middle-aged women in addition to increasing skin hydration, particularly among the older subpopulation.