Soybean, a legume native to Southeast Asia, serves many nutritional and medical purposes due to its rich source of phytochemicals and its antioxidant activity. Many animal and in vitro studies have demonstrated its potential impact on dermatologic health. The objective of this review is to investigate the clinical response of soy-based oral supplementation or topical application on dermatologic outcomes. A systematic review of studies assessing soy supplementation or application was performed in January 2023. Databases included PubMed, Embase, Cochrane, and Natural Medicines, and studies assessing any formulation that included soybean or associated products were included. Thirty studies met the inclusion criteria and are included in the review; 13 of these studies assessed oral supplementation and 17 assessed topical application. Topical and oral supplementation demonstrated efficacious results for a variety of dermatologic parameters, including chronological or photoaging parameters, skin barrier status, hydration, hyperpigmentation, dermal network composition, erythema, hair and nail parameters, acne lesion counts, and vulvar lichen sclerosis scores. Factors associated with aging, such as wrinkle area and depth, were most frequently assessed among the studies, and both topical and oral studies demonstrated efficacy. Effects are likely mediated by dermal compositional changes, such as increased collagen and/or elastic fiber numbers. Transepidermal water loss measurements, an indicator of skin barrier status, were frequently obtained among the studies, although improvement was more likely achieved with topical application compared to oral supplementation. The results of this review highlight the utility of soy-based products for a variety of dermatologic applications, although future studies are required to determine optimal formulations and application routes for intended outcomes.
Keywords: Glycine max; acne; aging; collagen; eczema; hair; hydration; isoflavones; soy; soybean.