When you hear the word Soy, you probably associate it with soy sauce or tofu, not skincare. But as it turns out, the soybean has a bunch of useful active components and soybean extract is an interesting cosmetic ingredient with a wide range of possible effects.
Its main active components are antioxidant phenolic acids and flavonoids as well as small and large soy proteins. The large proteins give soybean extract nice skin smoothing and softening properties, while the small proteins (soybean trypsin inhibitor (STI) and Bowman-Birk inhibitor (BBI)) are thought to inhibit skin pigmentation and delay hair regrowth.
Regarding skin pigmentation, the soybean extract works by hindering melanosome transfer, meaning it blocks the melanin pigment from traveling up to the surface of the skin and becoming visible there. This is useful for most pigmentation situations but, if you have melasma, soy is not for you as melasma is estrogen-mediated and soy is a well-known phytoestrogen.
The most famous and bioactive flavonoids in soybeans are the isoflavones called genistein and diadzein that have potent antioxidant and anti-inflammatory properties. Genistein is also proven to inhibit UV induced redness in human skin. These isoflavones are also the ones that make soy a phytoestrogen, meaning they have a (weak) estrogenic effect. Topical estrogen is known to decrease skin thinning and collagen loss and soy might be able to do the same, especially during and after menopause when natural estrogen levels run low.
There is also some promising, but as yet not in-vivo (done on real people), research that soybean extract can stimulate both elastin and collagen synthesis and thus lead to healthier, younger-looking skin.
Overall, soybean extract is a promising and multi-functional active, a nice addition to most ingredient lists.
Show me some proof
- Waqas, Muhammad Khurram, et al. "Dermatological and cosmeceutical benefits of Glycine max (soybean) and its active components." Acta Pol Pharm 72.1 (2015): 3-11.
- Baumann, LESLIE S. "Cosmeceutical critique: soy and its isoflavones." Skin & Allergy News 32 (2001): 17.
- Zhao, Renbin, et al. "Extracts from Glycine max (soybean) induce elastin synthesis and inhibit elastase activity." Experimental dermatology 18.10 (2009): 883-886.