Ingredient Investigation: Soy and Vitamin C


Soy and vitamin C have been longstanding key ingredients in skin care products. Linda Walker, author of The Skin Care Ingredient Handbook, discusses the benefits of vitamin C and debunks the controversy surrounding soy. 

Soy: The Powerhouse (and controversy)

Soybeans uniquely contain all the necessary amino acids to support protein building in the body. This is critical to build collagen and to protect against enzymes that attack healthy collagen and elastin. Soy also contains a potent antioxidant called isoflavones. These isoflavones can protect against inflammation, inhibit tyrosinase, and stimulate autophagy (removal of protein debris). Soybean oil contains high levels of vitamin E and fatty acids. Soy lecithin is made from soybean oil and is high in choline, a nutrient vital to cell membrane development. Considerable anti-aging/antioxidant power resides in soy; so why the controversy? Soy isoflavones are also potent phytoestrogens, similar to human estrogen and can cause hormonal effects. Because of this, they are the subject of considerable research (based on “eating” soy foods) and the hormonal implications to cancer survivors. There is much data online about this. Regarding “topical” use of soy in skin care products, soy protein is what contains the isoflavones—soybean oil has none and soy lecithin has tiny to zero levels. In other words, it’s the form of soy that matters. Many soy ingredients in skin products have no isoflavone content, therefore no hormone implications. What about soy allergies and soy ingredients in skin care products? Since research is currently limited, if someone is highly allergic to soy internally, the safest choice may be to avoid topical use.

Vitamin C: Continues to Shine

At least 18 years ago, vitamin C appeared as a key active in skin care products. There’s a reason for this long and continuing reign as a master anti-aging/antioxidant ingredient. Vitamin C is necessary for wound healing, collagen formation and stability of intracellular tissue. It also brightens while toning pores and creating overall radiance. You’ve likely noticed the appearance of new types of vitamin C on numerous product INCI lists or marketing materials. Each claims varying levels of stability, bio-availability, molecular weight, penetration and general efficacy. Some vitamin C names you may see: L-ascorbic, ascorbyl palmitate, ethyl ascorbic; magnesium ascorbyl phosphate; sodium ascorbyl phosphate; tetrahexyldecyl ascorbate; ascorbyl glucoside and ascorbyl methylsilanol pectinate. Research indicates certain vitamins and minerals can compete with each other for absorption, when taken internally. Vitamin C and copper is one of these combinations. There is less research regarding “topical” combination, but it may make sense to use skin care products containing them at alternate times.

This information was provided by Linda Walker, author of The Skin Care Ingredient Handbook, now available from

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