Dulse: Nutrients, What Research Shows and Safety

Dulse (Palmaria palmata) is a reddish-purple seaweed that grows on cool North Atlantic and Pacific coasts. People eat it dried, as flakes or powder, or soaked and added to salads, soups and breads. This page keeps the whole food apart from extracts and from hype, and it starts with the safety point that matters most: iodine.

Read this first

• Dulse is a high-iodine seaweed, and the amount changes with the season and place it was harvested. A 2025 Arctic study worked out that only 0.63 to 0.92 g of dried dulse a day would fit a 70 kg adult's iodine limit at its higher-iodine times of year. [1] That is the authors' calculation, not an official serving.
• Too much iodine can disturb the thyroid. The American Thyroid Association says intake above 1,100 mcg a day is not recommended, and that infants, older adults, pregnant or breastfeeding women and people with thyroid disease are more at risk. [2] If you have thyroid disease or take thyroid medicine, ask your clinician before eating dulse often.
• In Norway, regular seaweed eaters (dulse was one of the common species) often had intakes above the upper limit, and TSH fell when they stopped seaweed for six weeks. [5] [6]
• Arsenic, cadmium and lead were measured in Arctic dulse and changed with the season. [1]
• Evidence summary: dulse is a nutrient-rich food. Benefit claims such as "reduces inflammation" come from lab work on extracts, not from trials of eating dulse. [8]

What is in it (USDA values)

No USDA entry for this food. USDA FoodData Central (SR Legacy) has no dulse item, so we give no per-100 g table. We would rather show no number than an invented one.

What we did read: in a 2024 laboratory comparison of dulse, knotted wrack and Irish moss, dulse had the highest protein of the three. [3] A 2025 Arctic study found that dulse's protein and ash rose in late winter and spring and fell in late summer and autumn, with the lowest protein in August. [1] The same study found that sugar and dry matter were higher in late summer and autumn. [1] A 2025 laboratory analysis found the carotenoids lutein and alpha-carotene in dulse extract. [9] Those are lab measurements of a prepared extract, not trials in people.

We did not find a source with iodine in mcg per gram of dulse; the Teas 2004 survey of 12 seaweeds ranged from 16 mcg/g in nori to over 8,000 mcg/g in processed kelp granules, and its abstract does not list dulse. [4] Always check the product label, because labelling of iodine was missing for many seaweed products in Norway. [5]

What research says

Food vs extract. The Norwegian findings are about the whole seaweed as eaten. [5] [6] The neutrophil study used an extract, which is a different product. [8] Species, harvest place and processing change composition, so one number cannot describe every bag.

How much is a normal serving

There is no official serving for dulse that we could find. The only figure we read is the Arctic authors' calculated maximum of 0.63 to 0.92 g dry weight a day for a 70 kg adult, based on iodine at the study's higher-iodine times of year. [1] This is information, not a prescription, and your own situation may differ. In the Dutch market study, iodine in seaweed products ranged from under 0.1 to 7,910 mcg per gram fresh weight, and a quarter of regular seaweed eaters were above a 600 mcg a day limit. [7] Cooking in water may move some iodine out of food, but we did not read a dulse-specific figure. [4]

Safety, allergy and medicines

• Iodine. The ATA advises against iodine or kelp supplements giving more than 500 mcg a day, and says the upper limit is 1,100 mcg a day. [2] NHS says adults need 140 mcg a day and that long-term high doses could affect the thyroid. [10] A review warns that even small amounts of some brown seaweeds can have antithyroid action and that labels may not say. [11] Dulse is a red seaweed, and we did not find a source comparing it directly with kelp.
• Thyroid disease and medicines. The ATA says people with existing thyroid disease are susceptible to adverse effects of excess iodine. [2] Talk to your clinician before eating it regularly. We did not read a source on dulse and specific medicines.
• Pregnancy, breastfeeding, children. The ATA names these groups as more vulnerable, and gives an upper range of 500 to 1,100 mcg a day in pregnancy and breastfeeding. [2] We did not find a dulse-specific official statement.
• Metals. Arsenic, cadmium and lead were found in Arctic dulse and were higher in winter and spring. [1] We did not read which forms of arsenic dulse contains. See the heavy metals and contaminants page.
• Allergy. Allergy societies say seafood allergy is caused by proteins in fish and shellfish, not iodine. [12] Dulse is not fish or shellfish. We did not read a source on seaweed allergy. If lips, mouth or throat swell or breathing is hard after eating, call 911 or your local emergency number. [13]
• Vitamin K, potassium, kidney disease, sodium. Proper evidence not found in the sources we read for dulse specifically; check with your clinician if you take warfarin or have kidney disease.

Choosing, storing and food safety

• Look for products that state the iodine content; labelling was missing for many seaweed products in Norway. [5]
• Keep to the product's storage directions; we did not read a dulse-specific food-safety source.
• Powder and flakes pack more dry seaweed per spoon than leaves, so spoon size matters. [1]

Related pages

• Iodine in seaweed: how much by type
• Heavy metals and seaweed
• Seaweed in pregnancy and breastfeeding
• Seaweed iodine and thyroid
• Kelp and seaweed supplements
• Nori