A new study, funded by the United Soybean Board and Soy Nutrition Institute Global and carried out by researchers at Integrative Skin Science and Research, in California, aimed to investigate how oral supplementation of a soy protein isolate with added isoflavones (SPII) affects facial wrinkles, dyspigmentation, hydration and sebum excretion in 44 postmenopausal women at heightened risk of photoaging.
Their study provides data suggesting average wrinkle severity decreased in the supplemented participants at weeks 16 and 24, by 5.9% and 7.1%. What's more, compared to the casein group, average wrinkle severity was significantly decreased and facial pigment intensity was decreased by −2.5% (p < 0.05).
The authors conclude that supplementation with a standardised, multicomponent soy protein isolate with added isoflavones may improve facial wrinkle severity, reduce skin pigment intensity, and increase skin hydration in postmenopausal women.
What we know
Plant-derived isoflavones are naturally occurring nonsteroidal compounds that resemble estrogens and are commonly classified as phytoestrogens.
Due to their structural similarity to estradiol, isoflavones are able to bind to estrogen receptors and even mimic their actions.
Specifically, isoflavones can bind to ERα and ERβ receptors, which have been shown to interact with keratinocytes and fibroblasts in the skin, therefore can encourage wound healing, promote cell proliferation, act as antioxidants, and exert anti-inflammatory and anti-cancer properties.
In the skin, isoflavones and other phytoestrogens have been shown to increase hyaluronic acid concentration. One pilot study showed that the use of an isoflavone-rich soy extract for six months in postmenopausal women significantly increased epithelial thickness, elasticity, collagen fiber quantity, and angiogenesis.
Soy isoflavones also contain serine protease inhibitors that mediate protease-activated receptor-2-mediated phagocytosis of melanosomes by keratinocytes, thereby minimizing melanin pigment transfer to surrounding keratinocytes in the skin.
In cell culture and animal studies, soy isoflavones have been shown to protect against ultraviolet type B-related cells death, erythema, skin barrier dysfunction, and depletion of the skin’s natural antioxidant enzyme catalase. Soy isoflavones also reduce skin hyperpigmentation through a reduction in melanin transfer from melanocytes to keratinocytes.
In-vitro evidence suggests soy-derived peptides are similar to collagen-derived peptides in stimulating collagen synthesis in dermal fibroblasts.
Postmenopausal women are more susceptible to facial aging due to a shift in hormonal balance and decrease in collagen synthesis making this an important audience for research.
The current study builds on all of these preliminary studies to comparatively study soy protein containing isoflavones (SPII) against a calorie-matched casein protein without added isoflavones.
This 6-month prospective, randomised double-blind controlled study was conducted on 44 postmenopausal women (all with Fitzpatrick skin types 1, 2, and 3) who were randomised to receive a drink supplement made with either casein protein or SPII (30 g/d of soy protein powder containing 50 mg of isoflavones daily).
A high-resolution facial photography system was used to measure wrinkle severity and pigmentation at 0, 8, 16, and 24 weeks. Skin biophysical measurements included skin hydration and sebum production.
The average wrinkle severity was decreased in the SPII intervention group at week 16 and week 24 by 5.9% and 7.1%, respectively, compared to the baseline. Compared to the casein group, average wrinkle severity was significantly decreased at week 16 (p < 0.05) and week 24 (p < 0.0001). Facial pigment intensity was decreased by −2.5% (p < 0.05) at week 24. There was no significant change in the casein group.
Compared to baseline, skin hydration in the SPII group was significantly increased by 39% and 68% on the left and right cheeks (p < 0.05), respectively, at 24 weeks. There were no significant differences in sebum production. Dietary soy protein supplementation with isoflavones may improve skin photoaging, including wrinkles and dyspigmentation, and increase skin hydration in postmenopausal women with Fitzpatrick skin types I, II, and III.
Noting limitations of the study, the team states they had a relatively small sample size with all subjects being postmenopausal women with more photoaging-prone skin, and the soy and casein were provided as protein powders that required the intake of large volumes of water on a daily basis and led to equal levels of withdrawals from each group.
The authors note that studies assessing supplementation of a soy protein with added isoflavones with an expanded population including males, younger participants, and higher Fitzpatrick skin types are warranted.
Additionally, studies utilizing isolated soy protein and isoflavones to assess its effects on skin health may strengthen these associations. Since phytoestrogens may mimic estrogenic effects in the skin, future studies might also investigate the systemic effects of soy isoflavones in postmenopausal women from a gynecological or multidisciplinary perspective.
https://doi.org/10.3390/nu15194113 (registering DOI)
"Soy Protein Containing Isoflavones Improves Facial Signs of Photoaging and Skin Hydration in Postmenopausal Women: Results of a Prospective Randomized Double-Blind Controlled Trial"
Rizzo, J.; Min, M.; Adnan, S.; Afzal, N.; Maloh, J.; Chambers, C.J.; Fam, V.; Sivamani, R.K.