A brown seaweed barely uncovered at low tide
Alaria esculenta belongs to the order Laminariales, the same family as the large kelps. Some call it "Atlantic wakame", echoing its resemblance to the wakame most commonly found in shops, although it is a distinct species.
Eaten for centuries along the coasts of Northern Europe, it is now attracting research for a completely different reason: its biomass concentrates several families of molecules, polysaccharides, pigments, polyphenols, minerals and fatty acids, which make it an active field of study for cosmetics and nutraceuticals.
Why this seaweed grows almost nowhere in France
Alaria esculenta is a species of cold waters in the North Atlantic. It is found from Svalbard to Brittany on the eastern coast of the Atlantic, and as far as Iceland, Norway, Scotland and Ireland. It prefers cold, well-flushed waters strongly exposed to swell, where it colonises the rocks of the lower infralittoral fringe.
This distribution is due to a specific physiological constraint. Waters whose summer temperature reaches or exceeds 16°C become unfavorable to it, which explains its absence from the southernmost coasts of the English Channel and the North Sea. In France, Brittany thus marks the southern limit of its natural distribution area in Europe, with populations notably present on the coasts most exposed to swell, in the Iroise Sea.
This thermal sensitivity is not an anecdotal detail. It makes certain populations particularly vulnerable to the warming of coastal waters, a parameter that researchers continue to monitor.
From the giant blade to invisible spores: portrait of a kelp
A long olive-brown blade, which can reach several metres in good conditions, distinguishes Alaria esculenta at first glance. A thick midrib runs through its entire length, a feature that differentiates it from the large kelps with more uniform blades. The thallus attaches to the rock by a holdfast, extends by a short stipe, then by this large wavy blade whose flexibility contrasts with the mechanical resistance of the vein. At the base of the stipe appear small specialised blades, the sporophylls, whose role is less photosynthetic than reproductive.
The biological cycle of the species alternates between two organisms of radically different appearance. The large seaweed visible underwater constitutes the sporophyte, the diploid and macroscopic generation. Its sporophylls release microscopic spores which, once fixed on a support, give rise to male or female gametophytes, tiny and filamentous. The latter produce sex cells whose fertilisation forms a zygote, the starting point of a new sporophyte. This alternation between the macroscopic generation and the microscopic generation characterises all Laminariales.
A matrix of marine molecules, not a magic formula
No single molecule explains the interest in Alaria esculenta, and that is precisely what intrigues researchers. This seaweed owes its reputation to a balance between several families of compounds, embedded in the same biomass.
Fucoidans: custom-made polysaccharides, not a single molecule
Fucoidans are sulphated polysaccharides, rich in fucose, naturally produced by brown algae. Their structure varies considerably depending on the species, the season and the extraction process used. Norwegian researchers compared the purified fucoidans of three kelps, including Alaria esculenta: the fraction from the latter proved structurally different from those of the two other studied species, with a higher galactose content and a lower degree of sulfation.
In this same study, only two of the three species showed complement-inhibiting activity in the laboratory; that of Alaria esculenta did not show it in the tested conditions. Talking about "fucoidan" as a single molecule therefore remains scientifically imprecise: each species produces its own molecular signature.
Phlorotannins: the polyphenols unique to brown algae
Brown algae produce a family of phenolic compounds unique to them: phlorotannins. These molecules are studied for their antioxidant properties and for their interactions with certain mechanisms involved in skin ageing.
A study comparing extracts of three Icelandic algae measured, in Alaria esculenta, the highest phenolic content of the three species, with a DPPH radical scavenging rate higher than 90%, comparable to that of references such as ascorbic acid, gallic acid or alpha-tocopherol.
The same researchers observed, in vitro, a notable inhibition of several enzymes involved in the degradation of skin structures: up to 76.9% for collagenase and 72.8% for elastase in the tested conditions.
Fucoxanthin: the pigment that captures light
Fucoxanthin is the carotenoid characteristic of brown algae. Associated with chlorophyll, it participates in the capture of light necessary for photosynthesis and has, like most carotenoids, a recognised antioxidant capacity. Its concentration varies greatly depending on the season and culture conditions, which makes any quantified promise hazardous without a precise characterisation of the extract used.
Minerals and trace elements: a richness that needs monitoring
Like most macroalgae, Alaria esculenta naturally concentrates the elements present in seawater. Analyses conducted on populations cultivated in Ireland measured a particularly high content of potassium, magnesium, iron and zinc. This mineral richness has a downside: iodine, which is also present, must be closely monitored when the seaweed or its extract is intended for regular consumption, as well as arsenic and certain trace metals, whose levels depend heavily on the culture medium and the processing methods applied after harvest.
A lipid profile that needs qualifying
Brown algae are generally low in lipids compared to vegetable oils or fatty fish. The lipid fraction of Alaria esculenta nevertheless presents an interesting profile, rich in polyunsaturated fatty acids and notably in EPA (eicosapentaenoic acid), while DHA (docosahexaenoic acid) remains a minority. This nuance matters: Alaria esculenta constitutes an interesting marine matrix in polyunsaturated fatty acids, but it cannot be presented as a concentrated source of DHA comparable to microalgae oils.
What cosmetic research has shown, and what it does not yet show
Two research studies, conducted independently, shed light on the potential of Alaria esculenta for the skin.
The first, already mentioned, concerns extracts obtained by green extraction processes and shows promising antioxidant and anti-enzymatic activities in the laboratory.
The second was conducted directly on human skin cells from subjects of different ages: the researchers observed, for the first time in quantitative terms, an increase in the production of progerin (a protein associated with cellular ageing) with age, and showed that an Alaria esculenta extract could, in the tested conditions, reduce this production in aged cells.
These two research avenues explain why this seaweed has established itself as a raw material in certain cosmetic formulations designed for the comfort and appearance of mature skin.
It is in this spirit that Thaléïs Océan chose to combine Alaria esculenta with other active ingredients, rather than relying on an isolated molecule presented as sufficient on its own. In Crème Visage N°2, it joins Chondrus crispus harvested off Molène, hyaluronic acid, aloe vera and sweet almond oil, within a 100% natural origin formula made in France. This combined-ingredient approach is also in line with the science itself: as shown by the studies cited above, no isolated molecule alone explains the interest of a brown seaweed for the skin.
And on the nutraceutical side, a completely different logic
The nutraceutical approach does not seek the same evidence as the cosmetic approach. It is interested in the combination between fibres, polysaccharides, proteins, minerals, pigments and polyunsaturated lipid fraction, rather than an isolated skin effect. Recent works study Alaria esculenta as a functional food ingredient, with a particular interest in fucoidans, fucoxanthin, polyphenols and certain lipid fractions that can be isolated and then concentrated.
A real biochemical richness.
Alaria esculenta illustrates well the biochemical richness of the large brown algae of the North Atlantic. Its interest far exceeds its traditional food use: its ability to produce sulphated polysaccharides, polyphenols and pigments opens several avenues, in cosmetics as in nutraceuticals.
