Seaweed as Food and Medicine

In the summer of 2010, I went out to harvest kelp with Larch Hanson, who has been harvesting seaweed for the last 40 and more years up in WayNorth Maine, along with his son Jay and his apprentice, Micah Woodcock. We source all of our seaweed from Micah –

The alarm went off just before 2am. Before going to bed four hours earlier, I’d laid out wetsuit, hat, and anorak, and now I yawned as I pulled the layers on. To be honest, I hadn’t really slept too well; I was afraid I would sleep through the alarm.

I tried not to drink too much, and only filled my water bottle half full, because there’s no place to stop and pee and besides, it’s inconvenient in a coldwater wetsuit. Downstairs, Jay lent me his favorite pair of gloves, and we stumbled in the dark down to the water. It was amazingly dark, and there were ten million stars. We didn’t talk much. We met up with Larch, who had gone down before to arrange the boats, on the trail and I tried not to stumble on the roots and stones they knew like the backs of their hands (in the dark). We mucked out in the water to the boats, and we were off. It was the middle of June; I was freezing.

The bay Larch works is about three miles long, and we were headed right out to the end on this trip. There are some areas where he’ll use a motor (kept in good repair so that no oil leaks into the water), but he won’t get anywhere near the seaweed with it. So we motored as far out to our harvest point as he was willing to go, anchored the lead boat, and rowed in from there — Jay and I in the longer container boat, Larch in a smaller boat. Larch makes his own wooden boats; they’re sealed only with vegetable oil, to preserve the quality of the water — marine paints are tremendously toxic.

By now it was about 3:30 or quarter to four, and though the sky was lightening somewhat, it was still mighty dark. We dropped anchor and got to work: lean out over the low side of the boat, grab a long frond of kelp, say please, cut it at the base of the frond with a ginsu knife with the handle wrapped in neoprene (so it’ll float if I drop it, and also to make it easier to grip in my thick neoprene gloves), say thank you, and haul it into the boat. That last is easier said than done: kelp can be 18 or 20 feet long, and awfully heavy when it’s full of water. After a while, I found a rhythm: grab, say please, cut, say thank you, haul-haul-haul, grab again . . . body and breath working together. When I forgot to breathe, the effort was doubled.

The sky lightened slowly, which made it easier to grab the kelp: instead of reaching around in the dark, we could see what we were grabbing for. When we’d thinned the area around our boat, Jay would haul in the anchor and toss it a distance off, pulling us to a new area; I just kept grabbing and asking and cutting and thanking and hauling. Eventually the boat, about 16 feet long and five feet wide, was so full of seaweed that there wasn’t room for us to work. We piled it up so that we could move around again, and went back to cutting (and thanking). I kept thinking, wow, we have an awful lot here! We must be nearly done! We weren’t, though — not until there was so much seaweed that it was two or three feet up over the sides of the boat, and there wasn’t any room for us to move at all. Then finally we rowed back to the motor boat with Larch, tied up in a caravan, and headed, very slowly, home. The trip home took about an hour, and was by far the coldest thing I have ever experienced (and I have lived through winters in Vermont and Russia!).

When we arrived home, it was time for breakfast and hot showers (for us and our wetsuits); the tide wouldn’t be right for us to get the boats all the way up to the shore for another 90 minutes, so the seaweed would have to wait in the boats for a little while. After that, it was time to hang all that kelp on several football fields’ worth of laundry line (clothespins and all!) along the shore so that it could dry. It has to dry within 48 hours to retain its high quality, so weather conditions are watched very carefully. Breath and body together again here as we hang: exhale, bend to the basket of kelp, pick one, inhale, reach way up overhead and clip it on the line, exhale, bend . . . And then it’s just a normal day: work in the garden, work on the new drying sheds (which will enable good drying in less-than-perfect weather), run any errands in town, find time for household chores (and hopefully a nap!), etc. The whole house (Larch and all his apprentices, and any guests) have dinner together, and after everything is cleaned up, it’s nearly 10pm again, and the cycle starts over.

Larch and his handful of apprentices did this every day, every summer harvesting alaria (Alaria esculenta), bladderwrack (Fucus vesiculosis), digitata (Laminaria digitata), dulse (Palmaria palmata), kelp (Laminaria longicruris), nori (Porphyra umbilicalis), and rockweed (Ascophyllum nodosum). This last seaweed, rockweed, is usually used as a fertilizer, but the rest are culinary vegetables. When the weather isn’t good enough to be on the water and to dry the seaweed, seaweed orders are filled, dried seaweed is chopped for soupmix, woodwork is done, tools are mended, and chores are tended to. That far north in Maine, summer evenings are often chill enough to require a fire through the night, so the chopping of wood is always on the to do list.

Why bother? What would compel them to work so hard, year after year?


If you do only one thing to improve your health this year, let it be adding seaweed to your regular diet. Seaweed contains B vitamins, vitamins A, C, D (as ergosterol, a precursor), E, and K, as well as fiber and a whole host of bioavailable minerals, including calcium, chromium, copper, iodine, iron, lithium, magnesium, manganese, phosphorus, potassium, selenium, silicon, vanadium, zinc, and probably others. And until Larch came out to Boston to teach this spring, I thought that was all there was to it: seaweed is the original super food!

But seaweeds are far more complex than that, or perhaps, all foods are more complex than that — after all, if what you need is beta-carotene, a carrot is curative — and can be used medicinally just as land plants are. Of course we’ve all heard about seaweed in relation to thyroid issues, and when you consider their calcium content, you can see their benefit in cases of heart disease. But there’s more going on here!

Here are some ways you can use common local seaweeds as medicine, by system:

All seaweeds have a softening effect on the body, helping to maintain flexibility in general, and in the blood vessels in particular. Larch shared some clinical stories with us, and in one he mentioned to a middle-aged man with heart disease, “your life has been about hardening, but now your work is to soften.” Seaweeds improve the strength and flexibility of the blood vessels.

All seaweeds are high in minerals the heart needs — in particular, calcium and potassium. Insufficiencies of these minerals can lead to hypertension.

The algin in brown seaweeds has been shown to dissolve deposits in arteries — use 5-10 grams of Laminaria (kelp or digitata, in our area) per day, and treat for four to six months for systemic improvement.
Laminaria have also been shown in Japanese studies to reduce cholesterol levels and high blood pressure.

Fucoidan, a component found most in kelp, is believed to be responsible for the ability to discourage the formation of blood clots as effectively as Heparin but without negative side effects, according to Swedish studies.

Nori, in its normal life cycle, will completely dry out, and stay alive. When the water touches it again, it is still vibrant and flexible. For arteriosclerosis and other chronic hardened heart conditions, use nori that has been long-boiled in soup, for best absorption.

For anemia, which can have many causes these days, including blood loss and nutritional deficiency, but also medications, dialysis, and chemotherapy, look to dulse, kelp, and bladderwrack.

Finally, for those who seem to have lost their “internal compass” — don’t forget seaweeds! People need good quality, bioavailable iron, and all of the mineral-rich seaweeds can provide this! I like dulse in this case, because it is gentle in flavor and action.

If you need more iodine in the diet to support thyroid problems, 3-5 grams of seaweed 4 times per week is the ticket. But each weed is different, and each person is different. You can, believe it or not, overdose on iodine, so watch for an itchy rash, or if your client suddenly loses energy — these are signs of overdose. Digitata is the highest source of iodine, and kelp is just behind. Alaria has more moderate iodine levels, if the others seem too “overwhelming”. Of course, bladderwrack has also traditionally been used to improve thyroid function in this country, though in Japan kelp is favored.

Seaweeds can also be very effective in supporting diabetes: French studies show that the polysaccharides in seaweeds slow the flow of glucose from the intestines into the bloodstream, providing stability in blood sugar levels. Combine that with plenty of bioavailable chromium, which is essential for glucose utilization, and it’s clear seaweed should be a part of any diabetic protocol.

women’s reproductive
Laminaria is a key factor in balancing menopause, irregular cycles and PMS, as well as dealing with fibroids, cysts, and reproductive cancers. For issues around balancing hormones, go for kelp and digitata. For issues related to reproductive cancers, and in fact for any cancer, alaria is well-suited.

Lots of times kelp and digitata come up together — how do you know which one to use? I look to the environments in which they grow: Kelp grows in calm water; it grows straight up from the bottom in a long, ruffled frond with a firmly anchored stipe (stem). It is long, flexible, and tremendously strong, but it looks delicate and graceful in the water. Digitata grows around rocks in the pounding surf where the waves are constantly crashing it against the rocks. Its stipe is strong too, though its edges are straight and solid. In cases where either plant would work, I look at these personality traits to help me choose.

Of course seaweeds are also vital in prenatal preparations, as well as for nursing mothers. Seaweeds improve a woman’s ability to build a strong baby, improve milk flow, and help prevent mastitis.

Brown seaweeds are highly useful for yeast infections: they contain fucoidan, galactose, l-fructose, mannose, and xylose, (not to mention all those minerals!) all of which help balance sugar levels and make the body an unfriendly place for dysbiosis.

For those who suffer from hayfever and asthma, along with other dietary adjustments, include 5 grams of kelp in the daily diet.

For acute and chronic lung infections, Irish moss (Chondrus crispus) is the plant of choice. Boil the Irish moss down to a gel, and take it internally by the spoonful throughout the day for pneumonia and bronchitis. This is also very useful for chronic conditions such as emphysema, cystic fibrosis, and damage in the lungs from smoking and chemical exposure. In acute infectious cases, a steam of seasalt and kelp can also be very useful.

Seaweeds are invaluable to the immune system, in particular the brown seaweeds kelp and digitata. These are very high in fucoidan, a substance found in studies around the world to inhibit viral adhesion, as well as to actively fight against resistant strains of bacteria and virus. Most of the studies are using extracts; whole plant preparations, however, have been shown to have the same effects in smaller studies.

Red seaweeds (dulse, irish moss) have a particular affinity for the nervous system, and are particularly useful for cold sores, herpes, shingles, and Epstein-Barr, as well as MS. They inhibit viral reproduction, and can also be used topically for pain and blistering.

Many people know that kombu (one of the Laminaria species) is excellent for helping to break down the indigestible sugars in beans that can cause flatulence. If you eat beans, soak and cook them with kombu or kelp before eating them.

Once indigestion has hit, whether from beans or some other cause, make a strong tea of kelp or digitata: they help produce hydrochloric acid as well as soothing the mucosa of the stomach and intestines.

Kelp is also useful for gastric ulcers — there are studies that attribute this to the fucoidan, though I’d wager there are other components involved as well. Kelp is friendly to your flora, but tough on bacteria that may be associated with ulcers. Kelp has mucilage to help soothe ulcer pain, but Irish moss is the highest in this regard — boil it down to a gel and take it by the spoonful as needed. It should keep in the refrigerator for some time.

The red seaweeds dulse and irish moss work very much like cinnamon for constipation and diarrhea — they absorb excess water and increase in volume, so for constipation, boil them so that they will carry water into the intestines. For diarrhea, use them dried to absorb excess water in the intestines.

For topical issues, such as cuts, bruises, and burns, use the brown seaweeds kelp and digitata. They are disinfecting and can help wounds heal with less scarring.

Brown seaweeds are particularly useful for arthritis — Russian studies have shown kelp extracts to have 100 times the anti-inflammatory action of the prescribed medication. You can also use these seaweeds topically for local pain. Bladderwrack and nori can help slow joint deterioration, and bladderwrack can also be effective for gout as an external poultice. All of the brown seaweeds promote the formation of fibronectin, which keeps joints lubricated and flexible.

Nori is good for any connective tissue issues — again, cook it long for best absorption. For regular use when soup isn’t practical, you can make a very strong decoction and preserve with alcohol. Nori is also good for disc degeneration and broken bones — it’s “sea comfrey”!

In order for calcium to move into the bones, it has to stay in the blood stream. Calcium cabonate, a popular calcium supplement, doesn’t stay in the blood stream; bone meal powder is better; but seaweeds are best. They are the most bioavailable source of calcium, and are already pre-balanced with magnesium. Rockweed and bladderwrack are the highest in calcium, and should be included for anyone with osteoperosis.

It is critical that you source your seaweed carefully. Seaweeds pull metals and toxins, and they’ll do it wherever they are — so if you’re eating seaweeds from water that’s not clean, it’s already full of toxins. Consider it this way: seaweed takes out the trash, but you don’t want to eat seaweed that’s already carrying trash, because you want it to be able to take out your trash instead! For this reason, I avoid seaweeds from the Pacific, favoring instead far-north Atlantic seaweeds.

Seaweed also needs to be wild-harvested, because aquacultured seaweed is regularly grown in still, stagnant water. In order to be vibrant, seaweeds need to be exposed to surf — whether that’s crashing surf for digitata, or inland calm for kelp. It’s also important to eat seaweed that is local, since most of our imported food is irradiated at the borders.

Of course, we could write an entire article about the specific benefits of seaweed for cancer patients, from renourishment to their ability to actually dissolve tumors and fibrous cysts — perhaps that will be part two!

There are lots of ways to prepare seaweeds, though soup is probably my favorite — because it’s simple, but also because it’s traditional. The herbalist Phyllis Light teaches about decocting even leaves and flowers to extract the minerals from the plants, and when we’re talking about something as mineral-rich as seaweeds, a nice long-boiled soup seems like the perfect way to go. But it’s just as tasty added to stir-fry, to sauces as a seasoning, or softened and chilled as a salad. If people are skeptical about seaweed and if they eat rice, you can have them toss a handful of finely chopped seaweed into their rice when they set the pot to boil — the rice will absorb many minerals from the seaweed, and the flavor is really quite mild. It’s a great way to start for the wary palate!

My very favorite seaweed soup recipe is simple: Chicken bone broth, a handful of shiitake and maitake mushrooms, big handfuls of alaria, digitata, kelp, and bladderwrack, garlic and onion. Simmer well, then add a little bit of miso and season to taste. I like to add seasalt, pepper, and some crushed red chili pepper, or thyme and oregano for colds and flu.

For more information, inspiration, and excellent seaweed, contact Micah Woodcock at Atlantic Holdfast Seaweed – and read Seaweed: Nature’s Secret to Balancing Your Metabolism, Fighting Disease, and Revitalizing Body and Soul by Valerie Gennari Cooksley (Stewart, Tabori & Chang, 2007, paperback, 224 pages, $16.95).

This article was previously published in the Northeast Herbal Association’s quarterly journal, December 2010.


  1. […] local* but which we got during our last visit with Larch, and although none of it is seaweed that I personally harvested, I have done so with Micah and Larch. So I figure, that counts as […]

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