Supplementary Material for: Intake of soymilk-okara powder for 8 weeks induced the improvement of skin elasticity in Japanese women

Introduction: Soymilk-okara, a rich source of protein and dietary fiber, is a byproduct of soymilk manufacturing. We investigated whether soymilk okara intake improved skin conditions in Japanese women with self-reported constipation.
Methods: Thirty-seven Japanese women with self-reported constipation were included in this study. Two-thirds of the participants ingested 15 g of soymilk-okara powder daily for 8 weeks (okara group), whereas seasonal effects were evaluated in the remaining one-third (observation group). The participants’ body composition and skin conditions (stratum corneum hydration, transepidermal water loss (TEWL), and gross elasticity (R2; epidermis and dermis) of the malar and forehead were measured. Additionally, fecal concentrations of uremic toxins such as indole and p-cresol were analyzed.
Results: Eight participants withdrew consent during the study period owing to COVID-19 etc, and the final data analysis was performed using data from participants in the okara (n=19) and observation (n=10) groups. No significant interactions among stratum corneum hydration, TEWL, or epidermal gross elasticity of the malar and forehead in the okara and observation groups were observed. In contrast, interactions of the dermis gross elasticity of the malar and forehead in both groups (p = 0.065 and 0.043, respectively) were observed. In the okara group, negative correlations between the changes in uremic toxins and the difference in the dermis gross elasticity of the forehead were observed.
Conclusion: The intake of soymilk-okara powder improved skin elasticity, which may be a result of changes in the intestinal flora.

引言：豆浆豆渣（soymilk-okara）是豆浆生产的副产品，富含蛋白质和膳食纤维。本研究探讨了摄入豆浆豆渣是否改善了自我报告便秘的日本女性的皮肤状况。
方法：37名自我报告便秘的日本女性被纳入本研究。三分之二的参与者每日摄入15g豆浆豆渣粉，持续8周（豆渣组），其余三分之一用于评估季节效应（观察组）。研究测量了参与者的身体成分及皮肤状况，包括角质层水合作用、经表皮水分流失（TEWL）、颧骨与前额的总弹性（R2；表皮及真皮）。此外，还分析了粪便中吲哚、对甲酚等尿毒症毒素的浓度。
结果：研究期间，8名参与者因COVID-19等原因撤回知情同意，最终数据分析纳入豆渣组（n=19）与观察组（n=10）的受试者。结果显示，两组在角质层水合作用、TEWL或颧骨与前额表皮总弹性方面未观察到显著交互作用；相反，两组在颧骨与前额真皮总弹性上存在交互作用（p值分别为0.065和0.043）。在豆渣组中，尿毒症毒素的变化与前额真皮总弹性的差异呈负相关。
结论：摄入豆浆豆渣粉可改善皮肤弹性，这可能与肠道菌群的变化有关。