Astaxanthin, an ingredient for hair care?

With its red-orange hue, astaxanthin is a natural pigment found in certain marine plants and some fish. It is found in krill, crustaceans, plankton, lobster, trout, and salmon. The color of astaxanthin, in fact, explains their pinkish tint. However, the primary natural source of this pigment is a micro-algae: the Haematococcus pluvialis. It is from this algae that astaxanthin used in skincare is typically extracted. This active ingredient is mainly known for its antioxidant properties, which some studies have found to be superior to those of beta-carotene, vitamin C, and vitamin E. Today, astaxanthin is primarily used for skin care, but some of its effects could also benefit the scalp.

As of now, no clinical studies have evaluated the effects of astaxanthin on hair. However, some of its demonstrated properties in vitro or when taken orally could potentially be extrapolated and beneficial for hair health.

• Astaxanthin may potentially aid in combating scalp inflammations.

  Astaxanthin possesses anti-inflammatory activity that could potentially soothe sensitive scalps. Indeed, studies have shown that this pigment can reduce levels of matrix metalloproteinases and pro-inflammatory cytokines by inhibiting the activity of IκB kinase, a complex responsible for controlling the activation of nuclear factor kappa B (NF-κB). This keeps NF-κB, a pro-inflammatory signaling pathway, inactive in the cellular cytoplasm and helps to reduce inflammation. As an integral part of the epidermis, the scalp could also benefit from this property. Therefore, astaxanthin could be a helpful ally in preventing irritations and itchiness associated with scalp inflammation.

• Astaxanthin could potentially prevent hair loss.

  As previously mentioned, astaxanthin is a potent antioxidant. This fat-soluble molecule can insert itself into cell membranes and neutralize free radicals in both their water-loving and fat-loving parts. In doing so, astaxanthin protects skin cells, as well as scalp cells, from oxidative stress. This stress can notably weaken hair follicles, alter intracellular signaling, and promote their entry into the catagen phase, then the telogen phase, which corresponds to the time when hair falls out. Thanks to its antioxidant activity, it can be assumed that astaxanthin limits these phenomena and slows down hair loss.

  Furthermore, studies in vitro have shown that astaxanthin is a natural inhibitor of the 5-alpha-reductase enzyme. This enzyme plays a key role in the conversion of testosterone into dihydrotestosterone (DHT). DHT is an androgen hormone that binds to receptors in the cells of the dermal papilla and initiates a cascade of signals leading to the progressive miniaturization of follicles. This process is the cause of androgenetic alopecia, more commonly known as baldness. By modulating the activity of 5-alpha-reductase, astaxanthin could reduce the local concentration of DHT in the scalp and help maintain hair density. However, it should be noted that to date, these potential effects have not been directly studied in clinical trials.

• Astaxanthin may delay the onset of initial gray hairs.

  The antioxidant action of astaxanthin could also prove relevant in delaying the graying of hair. Indeed, oxidative stress plays a major role in this process. As a reminder, hair turns gray in response to the gradual decrease in the number and activity of melanocytes, the cells responsible for melanin production. Free radicals can target these cells and damage their constituents. They can cause DNA mutations, such as deletions, which means a loss of genetic material. This impacts the activity of the mitochondria, which in turn affects the melanin synthesis process by the melanocytes and accelerates the onset of gray hair. By trapping free radicals, astaxanthin could potentially have a protective effect on the color of hair fibers.

Even though hair lengths are composed of biologically inert keratin fibers, meaning they have no cellular activity, they are nonetheless exposed to external aggressions, particularly UV rays from the sun, which can alter their structure. Studies have shown that UVB rays penetrate about 5 μm deep into the fiber, primarily affecting the cuticle, or the outer layer, while UVA rays, with their longer wavelengths, penetrate deeper and influence the cortex, or the middle layer. Cysteine, an amino acid highly present in the cuticle and sensitive to UV, can undergo photodegradation by breaking its disulfide bonds, which impacts the cohesion and mechanical resistance of the hair.

Oxidation caused by UV rays does not only affect the scalp but can also damage the structure of hair fibers by weakening the cuticle and increasing its porosity.

Due to its antioxidant activity, astaxanthin could potentially play a protective role for hair, shielding it from oxidation and oxidative stress. This pigment could thus help to maintain the structure, strength, and shine of the hair. Indeed, when the hair fiber is strong and the scales forming its cuticle are properly aligned, hair appears shinier as it is able to reflect light. Of course, in the absence of clinical studies, this antioxidant protective effect on hair length remains theoretical for now and depends particularly on the ability of astaxanthin to bind to the hair's surface.

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• DHANKHAR J. & al. Astaxanthin : A potential carotenoid. International Journal of Pharmaceutical Sciences and Research (2012).

• TRÜEB R. M. The impact of oxidative stress on hair. International Journal of Cosmetic Science (2015).

• COLTELLI M. B. & al. Smart and sustainable hair products based on chitin-derived compounds. Cosmetics (2021).

• SAMARGHANDIAN S. & al. Anti-inflammatory action of astaxanthin and its use in the treatment of various diseases. Biomedicine & Pharmacotherapy (2022).