How to replace vitamin C?

The vitamin C plays a central role in cosmetics due to the numerous benefits it provides for the skin. As a potent antioxidant, it helps neutralize reactive oxygen species generated by UV radiation and pollution, supports collagen synthesis as an enzymatic cofactor, contributes to improving skin radiance, and regulates the melanogenesis, which is responsible for skin pigmentation. These various mechanisms of action of vitamin C explain why it is so widely used.

Vitamin C can be identified on ingredient lists under its INCI name "Ascorbic Acid".

However, despite these well-documented benefits, the use of vitamin C is not always optimal or suitable for all skin types or formulations. In its active form, L-ascorbic acid is intrinsically unstable and highly prone to oxidation, which imposes strict formulation requirements, notably a pH below 3.5. Yet, since the skin’s pH is around 5.5, this acidic pH can compromise the skin barrier and lead to irritation and discomfort in sensitive or already compromised skin. Furthermore, its hydrophilic nature limits its cutaneous penetration without specific conditions, and its efficacy depends heavily on concentration, the delivery vehicle, and the application method. For these reasons, it may be worthwhile to explore alternatives that can reproduce all or part of vitamin C’s biological effects while offering greater stability or enhanced tolerance.

When seeking to substitute vitamin C, the objective is to identify active compounds capable of mimicking its biological mechanisms. Several options are available, and their suitability depends on the desired outcome.

• Vitamin C derivatives.

  The most logical alternative to vitamin C is undoubtedly its derivatives. In cosmetics, these modified forms of ascorbic acid have been developed to overcome its primary drawbacks: instability in aqueous solution, the need for a highly acidic pH, and potential irritation on certain skin types. Vitamin C derivatives, such as the Sodium Ascorbyl Phosphate or the Ascorbyl Tetra Isopalmitate, offer improved chemical stability and can be more easily incorporated into formulations at physiological pH. Once applied to the skin, they gradually convert into active ascorbic acid, allowing you to enjoy the same benefits as the vitamin C.

  The interest in these derivatives is supported by several experimental studies. One study in vitro particularly focused on their ability to support collagen synthesis, one of the hallmark mechanisms of vitamin C. The results show that L-ascorbic acid dose-dependently stimulates type I collagen production by human fibroblasts, but vitamin C phosphate (VicC-P) and vitamin C glucoside (VicC-Glu) elicit comparable biological responses. In a reconstructed dermis model, these derivatives also promote extracellular matrix contraction, indicating a strengthening of the collagen network. The authors conclude that these stabilized forms can be regarded as true pro-vitamins.

• Other antioxidant active ingredients, such as green tea extract, ferulic acid, resveratrol, and astaxanthin.

  Vitamin C is not the only active ingredient capable of neutralizing free radicals and limiting oxidative stress. Other molecules also exhibit marked antioxidant activity, via complementary mechanisms. The green tea extract, rich in catechins such as epigallocatechin gallate, primarily acts by trapping reactive oxygen species. The ferulic acid, for its part, is a polyphenol capable of stabilizing free radicals while protecting cell membrane lipids from peroxidation, thereby helping to preserve skin barrier integrity. The resveratrol, notably found in grape skins, can also trap free radicals while activating certain antioxidant enzymes present in the skin, such as sirtuin-1.

  Finally, the astaxanthin stands out thanks to a unique molecular structure that allows it to embed itself in cell membranes and protect both their inner and outer surfaces against oxidation. This dual localization imparts this active ingredient with a remarkable efficacy in limiting oxidative damage. Some studies in vitro have even shown that astaxanthin’s antioxidant power can exceed that of vitamin C, making it an especially attractive option for individuals seeking to strengthen their skin’s antioxidant defenses.

• Other brightening active ingredients, such as niacinamide, licorice extract, or tranexamic acid.

  If the objective of using vitamin C is to diminish pigmented spots and even out skin tone, it’s important to know that it is not the only molecule capable of modulating melanogenesis. Other skin-brightening agents, such as niacinamide, licorice extract or even tranexamic acid, have also demonstrated notable efficacy against hyperpigmentation in various clinical studies. Their mechanisms of action are not all identical, as they can affect melanin transfer to keratinocytes, tyrosinase activity, or inflammatory pathways involved in post-inflammatory hyperpigmentation. Although these studies do not directly compare their efficacy to that of vitamin C, they show that these active ingredients represent credible alternatives for targeting pigmented spots, as summarized in the table below.

• BERNARD B. A. & al. Effect of vitamin C and its derivatives on collagen synthesis and cross-linking by normal human fibroblasts. International Journal of Cosmetic Science (2001).

• MONCADA B. & al. A double-blind, randomized clinical trial of niacinamide 4% versus hydroquinone 4% in the treatment of melasma. Dermatology Research and Practice (2011).

• TELANG P. Vitamin C in dermatology. Indian Dermatology Online Journal (2013).

• NAEINI F. F. & al. Topical tranexamic acid as a promising treatment for melasma. Journal of Research in Medical Sciences (2014).

• EKPE V. & al. Antioxidant effects of astaxanthin in various diseases - a review. Journal of Molecular Pathophysiology (2018).

• RAKHMINI A. & al. Comparison of 10%, 20% and 40% licorice extract cream as skin lightening agent. International Journal of Medical Reviews and Case Reports (2018).

• WINN D. & al. New topical tranexamic acid derivative for the improvement of hyperpigmentation and inflammation in the sun-damaged skin. Journal of Cosmetic Dermatology (2021).

• LAURENT A. & al. Pilot clinical safety and efficacy evaluation of a topical 3% tranexamic acid cream and serum protocol for managing facial hyperpigmentation in caucasian patients. Cosmetics (2024).