Soybeans in Beauty

Soy (kong, 콩) is the backbone of the Korean pantry. The Encyclopedia of Korean Culture lists the foods made from it: tofu, bean-curd pulp, doenjang, ganjang, bean sprouts, oil and soy milk. How the beans are fermented is the subject of fermented soybeans and making jang. This page asks a narrower question: does soy belong in beauty, and what has been shown?

What the old sources say

In the pre-modern record soy appears mostly as a cleanser ingredient. The Encyclopedia of Korean Culture's entry on face washing says households washed with bean powder together with lye or the water left from boiling soybean hulls, and a Korea Times feature lists soybeans among the beans ground into the cleansing powder jodu, covered under mung bean in beauty. The encyclopedia's soy entry itself mentions soap among industrial uses but says nothing about skin care.

Tofu water: no documentation found

Tofu-making leaves a liquid behind. The encyclopedia's tofu entry describes boiling and pressing soaked ground beans into soy milk, setting it with a coagulant such as calcium chloride, magnesium chloride or calcium sulfate, and draining the whey-like liquid from the curd. It does not mention any use of that liquid, or of tofu itself, on the face, and I found no Korean reference describing a tofu-water wash or tofu pack as a tradition. Home advice that presents one as an old custom is unsupported here. For tofu as food, see dubu and making dubu.

Soy in modern cosmetics

Soy reaches products in several forms: oil, protein and peptide fractions, isoflavone extracts such as genistein, and ferment filtrates, the last of which are covered in fermented ingredients in K-beauty.

What the research shows

• Systematic review. A 2023 review in the Journal of Clinical Medicine found 30 human studies of oral or topical soy: 13 oral (11 randomized) and 17 topical (one randomized, the rest self-controlled or open-label). The authors report benefits for wrinkles, photoaging and skin-barrier measures, but flag small samples (some arms of 5 to 10 people), multi-ingredient products that blur soy's own effect, and heavy reliance on uncontrolled designs. Two included studies were retracted or had duplicated images.
• Narrative review of menopausal skin. A 2025 review in Dermatology and Therapy gathered trials of topical genistein and oral isoflavones. In one 24-week study with 18 women per group, a 4 percent genistein gel thickened the epidermis by about 20 percent, against about 75 percent for an estradiol comparator. In a 2023 placebo-controlled trial of 50 women, a genistein cream improved hydration and wrinkles, but redness was higher in the genistein group. The review calls the area promising and says more research is needed.
• Recent oral pilot. A 2025 randomized pilot trial in Frontiers in Nutrition gave 66 postmenopausal women an 80 mg isoflavone capsule or placebo daily for 12 weeks. Crow's-feet roughness fell 5.6 percent in the soy group and rose 1.6 percent with placebo, a difference that was not statistically significant. Exploratory results in women who make S-equol (a gut-bacteria product of soy isoflavones) looked more promising, but those subgroups were small. The study was funded by a food-ingredient company.

None of these studies tested a bowl of food. Capsules and creams use defined doses, which is a different thing from eating tofu or doenjang. For the wider picture of food and skin, see diet and skin.

Evidence status

• Traditional use: soybeans as part of a cleansing powder are documented; tofu water or soy packs are not.
• Modern evidence: many small trials, often multi-ingredient, with mixed and sometimes industry-funded results.
• Practical note: soy is one of the major food allergens named by the U.S. FDA, so people with a soy allergy should read cosmetic labels and ask an allergist; see allergens in Korean food. Patch-test any new product.