Seaweed in Nutraceuticals and Pharmaceuticals

By Jayson Byles, forager & chef · September 2026

The shore we forage for the workshops is the same shore a growing ingredients industry draws on. Seaweed polysaccharides thicken medicines and dress wounds, seaweed extracts go into supplements and skincare, and research groups keep finding new things to do with compounds that only grow between the tides. This is a plain guide for the people who make those things: supplement and skincare developers, food and drink producers, and researchers who need to know what is in which species, what the evidence really shows, and where to get clean, identified raw material.

What is actually in seaweed

Seaweeds are not plants, and their chemistry is their own. Six families of compounds account for most of the commercial interest.

• Fucoidan. A sulphated polysaccharide found only in brown seaweeds. On our shore that means the wracks (Fucus vesiculosus, Fucus serratus), sugar kelp (Saccharina latissima), oarweed (Laminaria digitata), dabberlocks (Alaria esculenta) and sea spaghetti (Himanthalia elongata). It is the compound behind most seaweed supplements, and the one with the widest gap between laboratory promise and human evidence.
• Alginate. The structural polysaccharide of every kelp and wrack, and the seaweed compound with the longest record in real medicine. It forms gels that hold water, so it turns up in wound dressings, controlled-release tablets, antacid preparations and dental impression material.
• Laminarin. The kelps’ storage sugar. Studied as a prebiotic and immune modulator, and used as an agricultural biostimulant.
• Fucoxanthin and phlorotannins. The pigment that makes brown seaweed brown, and the polyphenols that make the wracks taste the way they do. Both are antioxidants in the test tube; phlorotannins are the more established skincare active, and bladderwrack is the richest source we cut.
• Carrageenan and ulvan. The sulphated galactans of the red seaweed carrageen (Chondrus crispus) and the sulphated polysaccharide of the green sea lettuce and gutweed (Ulva species). Carrageenan has gelled food and medicines for a century; ulvan is the newer interest, mainly in wound-healing hydrogels and biomaterials.
• Nutrients. Dulse (Palmaria palmata) carries useful protein, iron, calcium and iodine with vitamins A to D. Every seaweed carries iodine, the kelps in large amounts. Pepper dulse (Osmundea pinnatifida) is a flavour and fragrance ingredient, prized in small quantities.

Where it is used today

As excipients and materials. This is the mature end of the market. Alginate and carrageenan are pharmacopoeial ingredients (reviewed here): alginate dressings for exuding wounds, alginate and carrageenan matrices for controlled drug release, hydrogels for tissue engineering and 3D bioprinting. Nobody argues about the evidence here; the argument is about grade, purity and supply.

In supplements. Fucoidan and fucoxanthin sell as capsules on the strength of antioxidant, anti-inflammatory, immune and anti-obesity results in cells and animals. The human trials are small and inconsistent. A recent systematic review of fucoidan alongside cancer treatment found four usable studies and no consensus, and a review of fucoxanthin counted a single clinical trial in five years. A Mayo Clinic trial of fucoidan against chemotherapy-related fatigue is due to report in 2027, which is the kind of study the field needs. Until then, honest labelling stays with what is authorised, and the section on iodine below explains what that means.

In skincare. Phlorotannins, ulvan, fucoidan and the sun-screening amino acids found in red seaweeds all appear in cosmetic formulations. Several Scottish skincare brands are built on Hebridean seaweed, and the ingredient story, a clean northern shore, is a large part of the appeal.

In research. The early-stage work is where the surprises are. Five lines worth watching, all published in the last year or two:

• Methane from cattle. A bromoform compound from the red seaweed Asparagopsis cut methane by 49 to 77% in an eight-week University of Adelaide trial of 80 Angus cows, and a meta-analysis across trials puts the average at around 47%. Asparagopsis is a warm-water species, not one of ours, but the search for the same effect in cold-water seaweeds is under way (Adelaide, 2026).
• Natural sunscreens. Mycosporine-like amino acids, the UV filters red seaweeds make for themselves, are being screened and formulated as sunscreen actives, including chitosan nanoformulations that stabilise them on skin (Journal of Applied Phycology, 2026). Dulse and other reds are the sources.
• Fucoidan as a drug carrier. Beyond capsules, fucoidan is being built into nanoparticles that carry other drugs and target tumour cells, still at cell and animal stage (review, 2025).
• Packaging without plastic. Notpla’s seaweed coatings for disposable cups and boxes are plastic- and PFAS-free and won a €4 million Horizon Europe grant to scale (EU4Algae). Alginate and carrageenan do the work.
• Batteries and sensors. Seaweed carbon activated in plain seawater has been made into electrodes for a zinc hybrid battery capacitor, and seaweed polysaccharide hydrogels are being tested as flexible, biodegradable sensors. Both are laboratory work for now.

What almost all of this needs first is a modest, reliable quantity of one identified species. That is the gap a small hand-harvester can fill.

The iodine question

Iodine is the reason seaweed gets both praise and warnings. Adults need about 140 micrograms a day, according to the NHS, and it says supplements of 0.5 mg or less a day are unlikely to cause harm. Brown seaweeds can hold thousands of milligrams of iodine per kilogram of dry weight, which is why the British Dietetic Association advises against kelp supplements: the dose varies too much from label to label. Germany caps iodine in food at 20 mg per kilogram dry weight; France allows far more for brown seaweeds. If you are formulating, the iodine content of your raw material is the first number to measure.

On claims, the rules are simple. The authorised iodine claims in Great Britain and the EU say that iodine contributes to normal thyroid function, the normal production of thyroid hormones, normal cognitive function, normal energy-yielding metabolism, normal skin and the normal functioning of the nervous system, and they can only be used where the food is a source of iodine. There are no authorised claims for weight loss, detoxing or treating thyroid conditions, and no authorised health claims for fucoidan or fucoxanthin at all. Products that make them are advertising unlawfully.

Scotland’s seaweed economy

The Scottish Government’s 2022 study of the sector put it at roughly £4 million of turnover and 59 jobs, small but growing, with bioactives modelled as the fastest-growing segment at 7 to 10 per cent a year. Its scenarios run to £22 million a year by 2040 on wild harvest alone and £71 million with farmed seaweed added. Oceanium in Oban is biorefining seaweed into food ingredients and materials, the Hebridean Seaweed Company supplies technical ingredients from Lewis, and Scottish skincare brands have made the Hebrides an ingredient of their own. Scotland competes with France and Portugal in bioactives, and its case is clean water, cool seas and identity: a named species from a named shore.

Wild harvesting is licensed. Anything beyond personal use on Crown foreshore or seabed needs a licence from Crown Estate Scotland, granted once NatureScot confirms no unacceptable environmental risk, with the licence type set by expected volume. We harvest under those rules; our plain guide to the law explains how the line between the pot and the trade works.

What to ask a supplier

Whether you buy from us or anyone else, these are the questions that separate raw material you can build on from a bag of weed.

• Species, with the Latin name, and whether the batch is single-species.
• Which shore, and the date it was cut. Water quality follows from the first; freshness from the second.
• How it was harvested. Cut above the growing point on a rotation, or pulled. It matters for the bed and it matters for consistency next year; we cut, never pull.
• How it was handled: rinsed in clean seawater, chilled within hours, dried low and slow or hot and fast. Heat changes the chemistry.
• Whether batch testing is available: iodine, heavy metals, microbiology, and a certificate of analysis for the lot you receive.
• Whether what you intend to make is a novel food. Whole seaweeds with a history of consumption in Europe before 1997 are not; an extract or isolate usually is, and needs authorisation before sale. The Food Standards Agency’s guidance covers Great Britain.

Getting seaweed for your project

We supply every species we harvest except laver: fresh, cut on the low tide and chilled the same day, in 5 kg lots; or dried in small bespoke batches as whole leaf, pieces or flakes. Every bag carries the species, the shore and the date. Batch testing and a certificate of analysis are available on request. We drop off by hand across the East Neuk and Fife, courier chilled across the UK, and ship dried seaweed further afield. For a first project, ask for a sample pack of what is in season and tell us what you are making; we will say what is at its best for your dates and what we would cut for it.

Sources

The figures and findings above come from these sources; the reviews are open access.

• Understanding the potential scale for seaweed-based industries in Scotland (Scottish Government, 2022)
• Licensing of wild seaweed harvesting (Crown Estate Scotland)
• Iodine (NHS)
• EU register of nutrition and health claims (retained in Great Britain)
• Novel foods authorisation guidance (Food Standards Agency)
• Fucoidan and alginate from brown seaweeds: extraction, structure and biomedical applications (Frontiers in Plant Science, 2026)
• Algal phycocolloids: bioactivities and pharmaceutical applications (Marine Drugs, 2023)
• Alginate-based hydrogels in drug delivery and wound dressing (2020)
• Ulvan: a marine polysaccharide for biomaterial design (2025)
• Phycochemical constituents and biological activities of Fucus species (2018)
• Chemical constituents and biological properties of Chondrus species (2024)
• Nutritional value and bioactive properties of dulse, knotted wrack and carrageen (Life, 2024)
• Systematic review of marine algae-derived fucoxanthin (2022)
• Effectiveness of fucoidan as supplemental therapy in cancer patients: systematic review (2022)
• Fucoidan for preventing chemotherapy-related fatigue, Mayo Clinic trial (ClinicalTrials.gov)
• Risks and benefits of consuming edible seaweeds (Nutrition Reviews, 2019)
• Seaweed compounds in cosmetics and cosmeceuticals (Marine Drugs, 2021)
• Metals and iodine in seaweed: EU monitoring and limits (Eurofins)
• Seaweed compound shows major methane cuts in beef cattle (University of Adelaide, 2026)
• Meta-analysis of bromoform-containing seaweed feed additives on methane (Journal of Dairy Science, 2025)
• Evaluation of UV-sunscreen mycosporine-like amino acids (Journal of Applied Phycology, 2026)
• Chitosan nanoformulations of mycosporine-like amino acids (IJMS, 2025)
• Fucoidan-based pharmaceutical formulations and nanocarriers (International Journal of Biological Macromolecules, 2025)
• Notpla: seaweed coatings for single-use packaging (EU4Algae)
• Seawater-activated seaweed porous carbon for a zinc hybrid battery capacitor (Journal of Energy Storage, 2025)
• Polysaccharide-based materials for flexible electronics (2025)

Questions we get asked

Which seaweed has the most fucoidan?

Fucoidan is a brown-seaweed compound. In Scottish waters the wracks (Fucus species), sugar kelp, oarweed, dabberlocks and sea spaghetti all carry it; content varies with species, season and the part of the plant, so a sample tested for your intended extraction is worth more than a general figure.

Is it safe to eat seaweed every day?

Red and green seaweeds in normal culinary amounts are fine for most people. Brown seaweeds, the kelps especially, can carry very high iodine, so they are best eaten in small quantities and less often. The NHS puts adult iodine needs at 140 micrograms a day and says supplements of 0.5 mg or less a day are unlikely to cause harm.

Can I buy raw seaweed for extraction in the UK?

Yes. We supply identified, hand-cut Scottish species fresh in 5 kg lots or dried in small bespoke batches, with the species, shore and harvest date recorded, and batch testing or a certificate of analysis available on request.

Do I need a licence to harvest seaweed commercially in Scotland?

Yes, for anything beyond personal use on Crown foreshore or seabed. Crown Estate Scotland issues the licence once NatureScot confirms no unacceptable environmental risk, and the licence type depends on your expected volume. Personal-use gathering needs no licence.

What is the difference between food-grade and pharmaceutical-grade seaweed?

Food-grade seaweed is clean, identified and handled under food-hygiene rules. Pharmaceutical use needs a defined, tested raw material with documented species, batch and contaminant results, and the extract you make from it may need novel-food or medicines authorisation depending on how it is sold. The raw material is where both start.

This is a guide to the ingredient, not medical or regulatory advice. For claims, novel-food status and product authorisation, talk to the Food Standards Agency or a regulatory adviser before you launch.