Improvement in Skin Conditions by Consumption of Traditional Japanese Miso Soup and Its Mechanism

Abstract

The present study was undertaken to determine the beneficial effects of miso soup consumption on the skin. The women were divided into two groups: the first group consumed three bowls of miso soup per day (miso-consuming group) and the second group consumed three bowls of soup per day without miso (non-miso-consuming group or control group). The women in both groups continued their respective routines every day. Before and after the 2-week trial, the stratum corneum water content, elasticity, sebum amount and skin texture of both their cheek and corner of their eye were analyzed. The skin texture was measured according to the images taken through a digital microscope. The women in the miso-consuming group had a significantly higher the stratum corneum water content, and their skin elasticity and texture improved compared with those in the non-miso-consuming group. There was no significant difference in the sebum amount between the two groups. The questionnaire on individual skin conditions showed that consumption of miso soup tended to improve smooth make-up application. In addition, miso extracts were prepared to examine the effect on ceramide synthesis of epidermal keratinocytes using cultured cells. The findings revealed that miso extracts increased mRNA expression and activity of β-glucocerebrosidase, an enzyme involved in the synthesis of ceramides in the stratum corneum. These results suggest that daily intake of miso soup may improve skin moisture and some ingredients in miso may stimulate the increase of ceramides in the stratum corneum.