Guidance on the use of astaxanthin.

The astaxanthin is a natural red-orange pigment belonging to the carotenoid family, more specifically xanthophylls. It is widely found in the marine environment, particularly in crustaceans (krill, lobsters, shrimps) and certain fish (salmon, trout, mackerel). However, its primary natural source remains a freshwater micro-algae: Haematococcus pluvialis. Known for its potent antioxidant action, the astaxanthin is capable of effectively trapping free radicals before they damage skin or hair cells. Therefore, it is particularly beneficial in preventing premature ageing of the skin and hair fibres.

Studies have also shown that astaxanthin can promote collagen production by increasing the expression of TIMP-1, an inhibitor of matrix metalloproteinases, thus helping to maintain skin elasticity and limit the appearance of wrinkles. Finally, its anti-inflammatory action, demonstrated by the reduction of MMP and pro-inflammatory cytokines via the inhibition of IκB kinase, suggests a soothing potential for sensitive skin or irritated scalps.

How to use astaxanthin in topical application?

Astaxanthin is now incorporated into many skin and hair care products. To use them optimally and reap all the benefits of this active ingredient, several points must be considered.

• Which dosage of astaxanthin should one opt for?

  In cosmetic formulations, astaxanthin is typically present at concentrations ranging from 0.01 to 0.1%, percentages that may seem low but are in fact sufficient to take advantage of its antioxidant properties. To date, no scientific study has demonstrated the superiority of one concentration over another. The most important thing is to follow the manufacturer's instructions, which take into account the stability of the astaxanthin used and the potential synergy with other active ingredients in the product.

• At what time of the day should a treatment containing astaxanthin be applied?

  Non-photosensitising, astaxanthin can be used both in the morning and in the evening, according to the guidelines provided on the product. In the morning, it acts as an antioxidant shield, bolstering the natural defences of the skin and hair against external aggressors they may encounter throughout the day, such as UV rays or pollution. In the evening, it can support skin regeneration. It's worth noting that its natural orange-red colour may slightly tint products that contain it. Therefore, we advise you to let it fully absorb before potentially applying another treatment or makeup.

• Which form of astaxanthin should you choose?

  All forms of astaxanthin are not equal in skincare. Natural astaxanthin, extracted from the micro-algae Haematococcus pluvialis, is currently favoured for its antioxidant potency and well-established safety profile, but its use is not yet systematic. Studies in vitro have shown that natural astaxanthin is over 50 times more effective than the synthetic form in neutralising singlet oxygen and 20 times more effective in eliminating free radicals. This difference can be explained by their unique stereochemistries, with stereochemistry referring to the spatial arrangement of atoms in a molecule. These variations in stereochemistry are highlighted by the existence of three enantiomers, as shown in the figure below. Natural astaxanthin contains 100% of the 3S, 3S' enantiomer, while synthetic astaxanthin comprises a combination of the three enantiomers: 25% of 3S, 3S', 50% of 3R, 3S' and 25% of 3R, 3R'.

Beyond its cosmetic use, astaxanthin can also be consumed, in the form of capsules or gummies for instance. When taken orally, astaxanthin is believed to act more globally on the body, neutralising free radicals in tissues and cell membranes. It is also thought to have beneficial effects on the skin: this pigment could enhance skin hydration and reduce the appearance of wrinkles. Astaxanthin-based dietary supplements are also credited with a positive impact on the immune system, athletic performance, and fatigue.

Whether consumed in capsules or gummies, astaxanthin is currently viewed as a versatile active ingredient, bridging the gap between nutraceuticals and dermo-nutrition.

Several clinical trials have explored the impact of astaxanthin supplementation on skin quality. The doses generally studied range between 3 and 6 mg per day. This dosage appears to be sufficient for the active ingredient to exert its antioxidant effects, particularly on skin structural alterations related to UV rays. A randomised double-blind placebo-controlled Japanese study, published in 2018, evaluated the effects of a daily supplementation of 4 mg of natural astaxanthin for 10 weeks. The 23 participants, all in good health, then had their skin exposed to UV to measure the minimal erythemal dose, an indicator of sun sensitivity. The group that received astaxanthin showed an increase in the UV reaction threshold, indicating a better protection against sunburn. In addition, transepidermal water loss in the irradiated areas was significantly reduced, suggesting a better maintenance of skin hydration. Participants also noted a subjective improvement in the roughness and texture of their skin.

Even though astaxanthin can enhance the skin's protection against the sun, it cannot replace a sunscreen.

These findings align with a review of scientific literature published in 2021, which lists several clinical studies, including six randomised placebo-controlled trials. It highlights a significant improvement in the appearance of wrinkles, skin texture, and hydration levels after a few weeks of supplementation. Astaxanthin could potentially provide support against photoaging of the skin. Furthermore, no adverse effects have been reported to date following oral intake of astaxanthin at doses between 3 and 6 mg, although it should be noted that studies are often limited by their modest size.