Seaweed Therapeutics - Course Notes

Torey Posts: 5,395 admin
edited June 2021 in Wild Edibles & Medicinals

Seaweed Therapeutics

This was a really good course. Info on food & medicinal uses but also on topical use for skin care & relaxation as well as how good seaweed is for the planet. I certainly know a lot more about seaweed than I used to and I am looking forward to my next trip to a coastal area. I encourage anyone who lives in a coastal area or anyone who has an interest in the benefits of seaweed to take this course. This is a link for anyone who missed it in the original discussion.

Seaweeds are macroalgae. Some are the fastest growing organisms on earth. They are categorized as Reds (Rhodophyta), Browns (Phaeophyceae) and Greens (Chlorophyta), although there may be some browns that look more red and some greens that could look brown, depending on the species and the amount of time they have been exposed on the beach.

Food Uses

Seaweeds contain a significant amount of minerals and trace elements essential for health; 10-20 times more concentrated than in land plants. Vitamin B12 production in the body is enhanced by eating seaweeds and they are a good source of Vitamin D3. Eating raw seaweed is the best way to obtain optimal amounts of Vitamin C and iodine. When cooked, iodine is easily dissolved into the cooking water or evaporated off. However, cooking seaweed allows the breakdown of polysaccharides for easier digestion (sulphated polysaccharides are hot water soluble). Fermenting also helps breakdown the polysaccharides. It is recommended that small amounts of seaweed should be taken daily rather than larger amounts on a less regular basis. Seaweeds are high in soluble fibre.

Agar and carrageenan from red seaweeds and alginates from brown seaweeds have been used for a very long time in food for their gelling/thickening properties and are now widely used in the food industry.

High in free glutamates, seaweed enhances the flavours of foods such as fish, mushrooms and tomatoes. Without the dangers of monosodium glutamate. The umami taste of seaweeds can add flavour to plant based diets.

Dried seaweed will keep for up to 10 years retaining its nutrients, when properly stored.

Medicinal Uses

Seaweeds have a number of medicinal applications, depending on the type of seaweed. They are:

Immunomodulating – Anti-inflammatory cytokines reduce inflammation in the body which may assist with auto-immune conditions which are linked to high levels of inflammation in the body. Fucoidans in brown seaweed promotes activation of NK and T cells.

Antioxidant – Oxidative stress is related to cancer, cardiovascular disease, neuro-degenerative diseases and inflammation.

Anti-cancer – In vitro studies have shown that the ulvans in green seaweeds prevent the proliferation of cancer cells. Human trials are needed to determine the effectiveness of ulvans in promoting cell apoptosis (cell death).

Antihyperlipidemic – Ulvans in green seaweed assist the liver in converting LDL into bile acids which are eliminated from the body.

Antiviral – Antiviral activity has been found against a number of strains of various virus’, including Herpes, Newcastle disease, Japanese encephalitis, Dengue fever, Yellow fever, West Nile virus, Measles, HPV as well as Influenzas and other respiratory illnesses. Nasal sprays containing Carragelose have been or are being approved for use in the prevention of or reduction of symptoms in respiratory illnesses.

Antidiabetic – Fucoidans in brown seaweeds have shown a reduction in blood glucose levels and increased insulin sensitivity in studies using in vitro testing as well as animal and human studies.

TCM – Seaweeds in general reduce Yang and increase Yin helping to keep a balance. They are classified as cooling and moistening.

Individual seaweeds may have other specific healing properties.


This is the use of seaweeds in spa therapies (Thalassotherapies). The vitamins, minerals and other bioactive properties of seaweeds are easily absorbed by the skin. So, seaweed baths, wraps, steams, facials, foot soaks, etc. Some seaweeds are very good for exfoliating the skin, increasing localized circulation, while being emollient at the same time.


Persons with hyperkalemia (high levels of potassium) should avoid seaweeds.

Seaweeds have anti-coagulant properties so if you are on blood thinners you should discuss this with your medical practitioner or pharmacist. Check with your practitioner regarding seaweeds before surgeries, although following surgeries seaweeds may help prevent adhesions.

Too much or too little iodine may cause an imbalance in the thyroid. Work with a health care practitioner that can monitor thyroid health if there are any thyroid concerns.

Animal Feed

Animals fed seaweed (up to 10% of their diet) have been shown to have an increased production of higher quality eggs, milk and meat. Cows fed 3% seaweed (in particular a red seaweed, Asparagopsis)  decreased their methane output by up to 95%.

Planetary Health

Seaweed has been used as a fertilizer for millennia. You can compost seaweed or apply it directly to your garden in the fall and allow it to decompose over the winter and it will be ready to till in the spring. Or it can be made into a seaweed tea for a foliar spray.

Seaweeds de-acidify the oceans, reduce atmospheric carbon and add oxygen back to the atmosphere. Kelp forests help reduce coast line erosion.

At least one company has created fibre from seaweed. There are companies that are investigating biodegradable and edible packaging made from seaweed. Other companies are working on creating a bio-gas through the fermentation of seaweeds.

There are companies along the BC coast (and I am sure in other locations) currently investigating the commercial viability of farming seaweed, in particular, kelp.


Optimal harvest time in the Northern Hemisphere is from the winter solstice to the summer solstice. The best time to harvest is in spring at a very low (spring) tides. Make sure to check your tide charts. Just harvest a few fronds from each plant. Don’t remove the holdfast (part that holds the seaweed to the rocks or sea floor). Use caution when harvesting in warmer, more tropical waters as there may be more microbes that could create toxicity. As for any foraging get a good book and go with a local forager for your first time out.

Wash your seaweeds well in ocean water and hang to dry.

Contrary to popular internet rumours, studies have been done on West Coast seaweeds, that show there was only a very small spike increase in the radiation levels and it was only for 2 weeks following the Fukashima incident before dropping back to normal. It is suggested that it came in the form of rain clouds as opposed to contaminated seawater.

Following are links to the regulations on harvesting in some areas of North America. Check before you harvest. Some seaweeds are off limits unless you can find them as beach casts.

British Columbia, Canada,and%20Oceans%20Canada%20(DFO).

Nova Scotia, Canada

Newfoundland, Canada



California, USA

Oregon, USA

Washington, USA

Maine, USA