Efficacy of a soy moisturizer in photoaging: a double-blind, vehicle-controlled, 12-week study

Serine protease inhibitors (soybean trypsin inhibitor [STI] and Bowman-Birk protease inhibitor [BBI]) found in soybeans have been shown to inhibit melanosome phagocytosis by keratinocytes via protease-activated receptor 2 (PAR-2). Pre-clinical studies have confirmed the skin lightening potential of these molecules. In this study, we investigated the efficacy of a novel soy moisturizer containing nondenaturated STI and BBI for the improvement of skin tone, pigmentation, and other photoaging attributes. Sixty-five women, with moderate facial photodamage, were enrolled in the 12-week, parallel, vehicle-controlled study. Efficacy was monitored through clinical observation, self-assessment, colorimetric evaluations, and digital photography. The results showed that the novel soy moisturizer was significantly more efficacious than the vehicle in improving mottled pigmentation, blotchiness, dullness, fine lines, overall texture, overall skin tone, and overall appearance. Differences were significant from week 2 to week 12 for all above parameters (except dullness which started at week 4). In this study, we found that a moisturizer containing stabilized soy extracts is safe and effective, and can be used to ameliorate overall skin tone and texture attributes of photoaging.