There is no mistaking the current trend in the cosmetics industry to incorporate vitamins and plant derivatives into formulations in order to advertise products as healthy, natural, green, sustainable or possessing anti-aging properties. One popular claim suggests using vitamin C for hair growth. As an essential nutrient for health, vitamin C takes part in many cellular processes and must be ingested by humans in significant quantities as we do not manufacture it internally as some other species do. Centuries ago, it was common knowledge that deficiency in this nutrient (later identified as vitamin C) among sailors on long voyages and the malnourished poor caused a horrible condition known as scurvy. The condition was determined to be easily preventable with the consumption of relatively small amounts of fruit or vegetables that had abundant levels of vitamin C. It is critically important for optimal function of the immune system and for tissue growth regeneration. Clearly, vitamin C is well-established as a necessary substance for internal consumption. But, does it really have any benefits when used externally in skin and hair?
Vitamin C in Beauty Products
Perhaps not surprisingly, the answer is sometimes yes, sometimes no. Vitamin C is a popular component of many topically applied skin care products, where it has definite observed benefits when used above certain concentrations (5-15%). At the surface, it acts as an anti-oxidant, combating damage caused by free radicals created by environmental pollutants and ultraviolet radiation exposure. This can help prevent formation of new wrinkles that occur when free radicals are present on skin. Vitamin C has also been shown to penetrate and transfer to epidermal tissue where it aids in cellular repair and promotes collagen production. It is beyond the scope of this article to explore all of the mechanisms and variables by which vitamin C benefits skin, but clearly, it does provide some genuine value. Whether or not it provides benefits to hair is less dependent upon complicated cellular processes and more dependent upon some basic chemical properties.
Vitamin C is the common name for ascorbic acid, a small chiral molecule, in other words one that can occur in two different forms that are non-superimposable mirror images of one another. The type of ascorbic acid found in plants, synthesized in animals and used in cosmetic and food products is the left-handed molecule (levorotatory enantiomer) of ascorbic acid (L-ascorbic acid). For whatever reason, the right-handed version (dextrorotatory) does not occur in nature and the lab-synthesized version offers no benefits over its more readily available isomer.
Properties and Benefits
Vitamin C is a small molecule organic acid, with key structural features in common with other mild acids, such as acetic acid (vinegar) and citric acid. For this reason, ascorbic acid can act as a mild clarifying agent in shampoo and can be effective in helping remove mineral buildup accumulated on the surface of the hair. This improves the ability of the hair to accept moisture, which makes it more soft and supple and resistant to tangling and breakage. Also, the lower pH of acidic shampoos smoothes and tightens the cuticle surface, rendering the hair more evenly reflective and shinier.
The presence of multiple hydroxyl groups (oxygen-hydrogen, -OH) makes ascorbic acid extremely hygroscopic, meaning it attracts and binds water to itself. For this reason, vitamin C can act as a humectant and effective moisturizer in hair products when used in conditioners, leave-in conditioners and styling products.
Also, when included as a component in leave-in conditioners and styling products, vitamin C can act as an anti-oxidant, much in the same manner as in skin creams. Free radicals can cause structural damage to the proteins in hair, which can lead to split ends and breakage. They also can react with both natural melanin and synthetic dye molecules resident in the cortex of the hair strands and bleach color from hair, while simultaneously causing physical damage to it. For this reason, free radical scavengers, such as vitamin C can be quite useful in color retention and maintaining the health and integrity of hair. Ascorbic acid is water soluble and is thus not a concern for build up or accumulation on the surface of hair, even when non-mainstream cleansing methods are employed (low-poo, no-poo).
Oftentimes, vitamin C is used as a preservative or pH adjuster in hair care products and has no significant impact at all on final properties of the product. If it appears as one of the last few ingredients, below what is known as the one-percent line, you can be assured that this is the case.
Vitamin C for Hair Growth
The marketing materials for some hair care products claim that their vitamin-C containing formula can promote hair growth and repair an unhealthy scalp. While it is certainly true that ascorbic acid is capable of transfer to tissue and cells in specifically-formulated skin care products where it can participate in cellular processes, this isn't usually the case in shampoos and conditioners. The reasons for this are that the pH of hair care products is generally too high for the acid to be active and the concentration of the ascorbic acid is too low for there to be any benefit. For this reason, most of these types of products will have no significant impact to the scalp or hair growth. However, it is possible that a formula intended for direct skin application might be of some benefit to the scalp tissue. Whether this would promote hair growth is not certain, but a healthy scalp is in the best position to perform this function. This would probably fall into the category of “it couldn’t hurt to try in moderation.”
Some users have reported that some vitamin C-based products have felt drying to their hands and hair. This is going to be very dependent upon an individual’s hair and skin type as well as on the other ingredients in the formulation. It is doubtful that the vitamin C itself leads to dryness, but perhaps if coupled with harsh surfactants, a too-low pH or insufficient emollients and moisturizers, a product could produce that undesirable tactile feel. Always trust your own reaction to a product and use what works for you!