The pursuit of healthier skin transcends the realm of cosmetics, delving into the interplay between nutrition and dermatology. Soy contains multiple compounds that enhance skin appearance -- particularly isoflavones. A growing body of research indicates that soy supplementation contributes to both skin health and appearance through a variety of mechanisms, favorably influencing various dermatologic parameters such as hydration, elasticity, collagen synthesis, skin barrier function, fine lines, and wrinkles.1
Isoflavones, which are nonsteroidal compounds found in uniquely high amounts in soybeans, are classified as phytoestrogens.2The three isoflavones in soybeans are genistein, daidzein, and glycitein.3By binding to estrogen receptors (ERα and ERβ), isoflavones may exert some of the same effects as the hormone estrogen, although they may also exert effects opposite to those of estrogen. In other cases, such compounds may have no effects on tissues affected by this hormone.4,5Isoflavones are being studied for their anti-inflammatory, antioxidant, antimicrobial, and anti-cancer effects.6-9
Reducing the Effects of Skin Aging with Soy
As the body’s outermost layer of protection, the skin is subject to both extrinsic and intrinsic influences, which impact its structure and function as individuals age.10Skin aging can be impacted by a multitude of factors, including genetics, environmental exposures, lifestyle behavior, and the aging process itself.11As the skin ages, wrinkles, dryness, a diminished barrier integrity, and a reduction in the thickness of the epidermis may occur.10The decline in estrogen levels among postmenopausal women lead to diminished synthesis of the protein collagen, which can be regarded as a key factor contributing to alterations in the skin.12Evidence increasingly suggests soy isoflavones can help combat the effects of skin aging, potentially among both pre- and postmenopausal women.13
For example, a 2007 study evaluated the effects of soy isoflavones on skin health in premenopausal Japanese women. Twenty-six females were randomized to receive either a supplement of 40mg of soy isoflavones or a placebo daily for 12 weeks. Assessments of linear and fine wrinkles, particularly at the lateral angle of the eyes, were conducted throughout the duration of the study. The study found there were statistically significant improvements in fine wrinkles at week 12 and in skin elasticity at week eight when compared to the placebo group. Importantly, no adverse effects due to isoflavones were reported.14
One year earlier, a study in post-menopausal women examined the effects of isoflavones plus a cocktail of bioactives that included fish protein polysaccharides, white tea extracts, grape seed, tomato, vitamins C and E, zinc, and chamomile extract. Women were randomized to receive either the dietary supplement or a placebo twice daily for six months. Skin aging was assessed via clinical grading and photo evaluation of face, hands, and decolletage. At study termination, compared to the placebo group, women receiving the supplement experienced significant improvements in facial wrinkles, pigmentation, laxity, under eye dark circles, and overall appearance of the skin.15Although the results were impressive, the experimental design of this study does not allow a determination of the extent to which isoflavones contributed to the results.
A 14-week, randomized, double-blind and placebo-controlled trial conducted in 2014 has the same limitations as the previously cited study. In this case, postmenopausal women received a placebo or a mixture of isoflavones along with lycopene, vitamins C and E, and fish oil. A total of 166 women were enrolled and randomly allocated to three groups: test group 1 (n=51), test group 2 (n=53), and placebo group (n=55). Test group 1 contained higher levels of the active ingredients compared to test group 2. At study end, there was a significant improvement in skin texture and a reduction in depth of facial wrinkles in groups 1 and 2 compared to the placebo group. Also, skin biopsy analysis revealed increased levels of collagen in subjects in test group 2 compared to those in the placebo group.16
The above findings plus results from other studies17provided the justification for more specifically examining the influence of soy isoflavones on facial hydration, pigmentation, and wrinkles in postmenopausal women. In the last study, which was conducted by our research laboratory, women in the soy group (n=23) consumed 30g/d soy protein isolate that contained 50mg isoflavones, whereas the placebo group consumed 30g/d casein. Skin biophysical assessments and facial imaging were obtained at baseline, eight, 16, and 24 weeks. Women in the soy group exhibited a significant reduction in the average wrinkle severity: 5.9% at week 16 and 7.1% at week 24, compared to baseline and compared to the casein supplementation group. Imaging analysis also revealed a significant decrease in average facial pigment severity in the soy group of 2.4% at week 24 compared to baseline and the casein supplementation group. Additionally, the soy group experienced a significant increase in skin hydration in both cheeks at week 24, with the right cheek increasing by 68% and the left cheek by 39% when compared to baseline, whereas there were no significant changes in the casein supplementation group.18These results provide the most direct support currently available for the efficacy of isoflavones.
Conclusion
Soy isoflavones have garnered an increasing amount of attention for a variety of proposed benefits. Accumulating clinical evidence indicates these naturally occurring soybean components exert a range of beneficial effects on the appearance of the skin. The dose of isoflavones shown to be efficacious in clinical studies ranges from about 40 to 60mg/d, an amount provided by approximately two servings of soy foods. Future research is needed to determine the long-term effects of isoflavones and to gain more insight into the dose needed for optimal benefit.
- Clinical efficacy of topical or oral soy supplementation in dermatology: A systematic review. N.
- Křížová L, Dadáková K, Kašparovská J, Kašparovský T. Isoflavones. Molecules. 2019;24(6):1076. Published 2019 Mar 19. doi:10.3390/molecules24061076
- Zaheer K, Humayoun Akhtar M. An updated review of dietary isoflavones: Nutrition, processing, bioavailability and impacts on human health. Crit Rev Food Sci Nutr. 2017 Apr 13;57(6):1280-1293. doi: 10.1080/10408398.2014.989958. PMID: 26565435
- Kim IS. Current Perspectives on the Beneficial Effects of Soybean Isoflavones and Their Metabolites for Humans. Antioxidants (Basel). 2021;10(7):1064. Published 2021 Jun 30. doi:10.3390/antiox10071064
- Wood CE, Register TC, Franke AA, Anthony MS, Cline JM. Dietary soy isoflavones inhibit estrogen effects in the postmenopausal breast. Cancer Res. 2006;66(2):1241-1249. doi:10.1158/0008- 5472.CAN-05-2067
- Yu J, Bi X, Yu B, Chen D. Isoflavones: Anti-Inflammatory Benefit and Possible Caveats. Nutrients. 2016;8(6):361. Published 2016 Jun 10. doi:10.3390/nu8060361
- Rodríguez-Roque MJ, Rojas-Graü MA, Elez-Martínez P, Martín-Belloso O. Soymilk phenolic compounds, isoflavones and antioxidant activity as affected by in vitro gastrointestinal digestion. Food Chem. 2013 Jan 1;136(1):206-12. doi: 10.1016/j.foodchem.2012.07.115. Epub 2012 Aug PMID: 23017414. Natarelli, N. Gahoonia, J. Maloh and R. K. Sivamani.
- J Clin Med 2023 Vol. 12 Issue 12. Accession Number: 37373864 DOI: 10.3390/jcm12124171
- Dhayakaran, Rekha & Neethirajan, Suresh & Xue, Sophia & Shi, John. (2015). Characterization of antimicrobial efficacy of soy isoflavones against pathogenic biofilms. LWT - Food Science and Technology. 63. 10.1016/j.lwt.2015.04.053.
- Conklin CM, Bechberger JF, MacFabe D, Guthrie N, Kurowska EM, Naus CC. Genistein and quercetin increase connexin43 and suppress growth of breast cancer cells. Carcinogenesis. 2007 Jan;28(1):93-100. doi: 10.1093/carcin/bgl106. Epub 2006 Jun 15. PMID: 16777995.
- Csekes, E.; Račková, L. Skin Aging, Cellular Senescence and Natural Polyphenols. Int. J. Mol. Sci.2021, 22, 12641.
- Russell-Goldman E, Murphy GF. The Pathobiology of Skin Aging: New Insights into an Old Dilemma. Am J Pathol. 2020 Jul;190(7):1356-1369. doi: 10.1016/j.ajpath.2020.03.007. Epub 2020 Apr PMID: 32246919; PMCID: PMC7481755
- Rzepecki AK, Murase JE, Juran R, Fabi SG, McLellan BN. Estrogen-deficient skin: The role of topical therapy. Int J Womens Dermatol. 2019 Mar 15;5(2):85-90. doi: 10.1016/j.ijwd.2019.01.001. PMID: 30997378; PMCID: PMC6451761.
- Gopaul R, Knaggs HE, Lephart ED. Biochemical investigation and gene analysis of equol: a plant and soy-derived isoflavonoid with antiaging and antioxidant properties with potential human skin applications. Biofactors. 2012;38(1):44-52. doi:10.1002/biof.191
- Izumi T, Saito M, Obata A, Arii M, Yamaguchi H, Matsuyama A. Oral intake of soy isoflavone aglycone improves the aged skin of adult women. J Nutr Sci Vitaminol (Tokyo). 2007 Feb;53(1):57-62. doi: 10.3177/jnsv.53.57. PMID: 17484381.
- Skovgaard GR, Jensen AS, Sigler ML. Effect of a novel dietary supplement on skin aging in post- menopausal women. Eur J Clin Nutr. 2006 Oct;60(10):1201-6. doi: 10.1038/sj.ejcn.1602438. Epub 2006 May 3. PMID: 16670692.
- Jenkins G, Wainwright LJ, Holland R, Barrett KE, Casey J. Wrinkle reduction in post-menopausal women consuming a novel oral supplement: a double-blind placebo-controlled randomized study. Int J Cosmet Sci. 2014 Feb;36(1):22-31. doi: 10.1111/ics.12087. Epub 2013 Sep 18. PMID: 23927381; PMCID: PMC4265247
- Nagino T, Kaga C, Kano M, et al. Effects of fermented soymilk with Lactobacillus casei Shirota on skin condition and the gut microbiota: a randomised clinical pilot trial. Beneficial Microbes. 2017:1-10.
- Rizzo J, Min M, Adnan S, Afzal N, Maloh J, Chambers CJ, Fam V, Sivamani RK. Soy Protein Containing Isoflavones Improves Facial Signs of Photoaging and Skin Hydration in Postmenopausal Women: Results of a Prospective Randomized Double-Blind Controlled Trial. Nutrients. 2023 Sep 23;15(19):4113. doi: 10.3390/nu15194113. PMID: 37836398; PMCID: PMC10574417.
About The Author:
Nasima Afzal, Mildred Min, and Raja K. Sivamani, MD, MS, AP Nasima Afzal is a senior clinical research coordinator at Integrative Skin Science and Research. Her passion for nutrition and skin health has allowed her to make invaluable contributions to the field of clinical research.Mildred Min is a medical student at California Northstate University College of Medicine and an integrative dermatology research fellow at Integrative Skin Science and Research. Her passion for dermatology and integrative medicine stemmed from a personal history of dermatological conditions and comorbid psychiatric conditions. Her research interests include psychodermatology, clinical dermatology, and integrative dermatology.Raja K. Sivamani, MD, MS, AP is a board-certified dermatologist and practices as anintegrative dermatologist at Pacific Skin Institute. He engages in clinical practice as well as both clinical and translational research that integrates bioengineering, nutrition, cosmetics, and skin biology. With training in both Allopathic and Ayurvedic medicine, he takes an integrative approach to his patients and in his research. He has published over 150 peer-reviewed research manuscripts, 10 textbook chapters, and a textbook entitled Cosmeceuticals and Active Cosmetics, 3rd Edition with a passion for expanding the evidence and boundaries of integrative medicine for skincare.