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

Abstract

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.