What are the benefits of astaxanthin for hair?

What are the benefits of astaxanthin for the scalp?

Of an orange-red hue, astaxanthin is a pigment naturally found in certain marine plants and some fish. It is found in krill, crustaceans, plankton, lobster, trout, and salmon. The colour of astaxanthin indeed explains their pinkish tint. However, the primary natural source of this pigment is a micro-algae: the Haematococcus pluvialis. It is from this that astaxanthin used in cosmetics is generally extracted. This active ingredient is mainly known for its antioxidant properties, evaluated as superior to those of beta-carotene, vitamin C and vitamin E by some studies. Today, astaxanthin is primarily used for skin care, but some of its effects could benefit the scalp.

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

Astaxanthin could potentially assist 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 through inhibition of IκB kinase activity, a complex responsible for controlling the activation of nuclear factor kappa B (NF-κB). This keeps NF-κB, a pro-inflammatory signalling 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 an 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 neutralise 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 signalling 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 present in the cells of the dermal papilla and initiates a cascade of signals leading to the progressive miniaturisation 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 contribute to preserving 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 grey hairs.
The antioxidant action of astaxanthin could also prove relevant in delaying the greying of hair. Indeed, oxidative stress plays a major role in this process. As a reminder, hair turns grey in response to the gradual decrease in the number and activity of melanocytes, the cells responsible for melanin production. However, 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 grey hair. By trapping free radicals, astaxanthin could potentially have a protective effect on the colour of hair fibres.

Is astaxanthin beneficial for hair length?

Even though hair lengths are composed of biologically inert keratin fibres, meaning they have no cellular activity, they are nonetheless exposed to external aggressions, notably the sun's UV rays, which can alter their structure. Studies have shown that UVB penetrates about 5 μm into the fibre thickness, primarily affecting the cuticle, the outer layer, while UVA, with longer wavelengths, penetrates deeper and influences the cortex, the intermediate layer. Cysteine, an amino acid highly present in the cuticle and sensitive to UV, can undergo photodegradation by breaking its disulphide bridges, 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 fibres 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 assist in maintaining the structure, resilience, and lustre of the hair. Indeed, when the hair fibre is robust 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.