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Herb library · Seaweed · Palmaria palmata

Dulse

An edible red seaweed, sold dried and as a supplement. Two small trials found little benefit for cholesterol; in one, dulse bread nudged triglycerides, an inflammation marker and TSH upward.

Traditional use

An edible red alga, reported to contain anti-inflammatory and antioxidant compounds. Researchers have tested it baked into bread in Northern Ireland and in capsules in northern Japan, where it grows, for cholesterol and blood sugar.

What studies show

  • Limited· shows no benefit

    Cholesterol and blood sugar: in an 8-week Japanese trial of 104 adults with high LDL, dulse capsules (2 grams a day) did not lower LDL or change blood sugar compared with placebo; triglycerides fell a little in women only.

  • Limited

    Inflammation and thyroid: in a Northern Irish trial, healthy adults eating bread with 5 grams of dulse a day saw CRP (an inflammation marker), triglycerides and TSH (a thyroid hormone signal) rise compared with the control group. The changes stayed within the normal range.

Be careful of

Cautions

  • AmountSeaweeds carry iodine in highly variable amounts (ODS). The adult upper limit for iodine is 1,100 mcg a day, and the dulse bread trial above measured a change in thyroid signaling.
  • ConditionToo much iodine can cause goiter and an underactive or overactive thyroid. People with autoimmune thyroid disease can react to intakes safe for others.
  • InteractionHigh iodine intake with antithyroid drugs such as methimazole can cause hypothyroidism (ODS).
  • Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.

Sources

  1. The effect of consuming Palmaria palmata-enriched bread on inflammatory markers, antioxidant status, lipid profile and thyroid function (2016) (opens in a new tab) · NIH · read September 25, 2026
  2. Effects of Palmaria palmata on lipid metabolism and glycemic control in participants with hypercholesterolemia (2020) (opens in a new tab) · NIH · read September 25, 2026
  3. Iodine: Fact Sheet for Health Professionals (opens in a new tab) · NIH ODS · read September 25, 2026

Reviewed September 25, 2026.