Also Known As: Fucus, Kelp, Knotted Wrack.

Scientific Name: Fucus vesiculosus; Ascophyllum nodosum; other Fucus species.

Family: Fucaceae.

People Use This For:

Bladderwrack is used for thyroid disorders, iodine deficiency, goiter, obesity, arthritis, and rheumatism, "blood cleansing", to increase energy, constipation, bronchitis, decreased resistance to disease, and anxiety. Topically, bladderwrack is used for skin diseases, burns, aging skin, and insect bites.

Safety: No concerns regarding safety when used orally in appropriate doses. It is important to obtain traceable supply free from contamination (1 case of contamination with heavy metals reported in the 1970’s).1,2

Pregnancy and Lactation: Refer to a Medical Herbalist

Effectiveness: INSUFFICIENT RELIABLE EVIDENCE to RATE

Obesity: Preliminary clinical research suggests that bladderwrack in combination with lecithin and vitamins doesn't result in sustained weight loss. More evidence is needed to rate bladderwrack for this use (combined lecithin, kelp, multivitamin preparation involving 120 women over 2 years). 3 

Mechanism of Action: The applicable part of bladderwrack is the entire plant. Bladderwrack is a brown seaweed. Bladderwrack contains high concentrations of iodine, which is present in varying amounts. Bladderwrack is a source of fiber, minerals such as iron, and vitamin B12.2

Preliminary clinical research suggests bladderwrack may normalize the menstrual cycle and have estrogen balancing effects in premenopausal women. It may also balance progesterone effects4 (case reports on three patients). Preliminary clinical research suggests topical administration of bladderwrack extract might reduce skin thickness and other signs of aging.5

Adverse Reactions: Excess Iodine intake is rare in humans outside of radiation contamination or excessive amounts of seaweed (or seaweed extracts) intake over a prolonged period. There is one case report of heavy metal poisoning where arsenic poisoning occurred with ingestions of a contaminated kelp product. 6 Another case of arsenic-related poisoning with bladderwrack ingestion 400 mg three times a day for 3 months resulted in kidney damage.7

Interactions with Herbs & Supplements: Avoid Iodine supplements at the same time.

Interactions with Drugs:

Antithyroid Drugs: Theoretically, may result in additive hypothyroid activity, and may lower the level of availableThyroid hormones.8

Interactions with Foods: None known.

Interactions with Lab Tests: 

Radioactive Iodine Uptake: Theoretically, bladderwrack might interfere with the results of thyroid function tests using radioactive iodine uptake.2

Thyroid Stimulating Hormone (TSH): Theoretically, bladderwrack might increase serum TSH levels and test results.8

Thyroxine (T4): Theoretically, bladderwrack might increase serum T4 levels and test results.8

Interactions with Diseases or Conditions:

Iodine Allergy: Avoid bladderwrack use in people sensitive to iodine.8

Thyroid Disorders: Prolonged use or excessive amounts of iodides may exacerbate thyroid gland problems.8

Dosage/Administration: Dr Clare’s Blends: 1 gm per day No typical dosage.

Specific References: BLADDERWRACK

1. Baker DH. Iodine toxicity and its amelioration. Exp Biol Med (Maywood) 2004;229:473-8.

2. Phaneuf D, Cote I, Dumas P, et al. Evaluation of the contamination of marine algae (Seaweed) from the St. Lawrence River and likely to be consumed by humans. Environ Res 1999;80:S175-S182.

3. Bjorvell H, Rössner S. Long-term effects of commonly available weight reducing programmes in Sweden. Int J Obes 1987;11:67-71.

4. Skibola CF. The effect of Fucus vesiculosus, an edible brown seaweed, upon menstrual cycle length and hormonal status in three pre-menopausal women: a case report. BMC Complement Altern Med 2004;4:10.

5. Fujimura T, Tsukahara K, Moriwaki S, et al. Treatment of human skin with an extract of Fucus vesiculosus changes its thickness and mechanical properties. J Cosmet Sci 2002;53:1- Pye KG, Kelsey SM, House IM, et al. Severe dyserythropoeisis and autoimmune

6. thrombocytopenia associated with ingestion of kelp supplement. Lancet 1992;339:1540.

7. Conz PA, La Greca G, Benedetti P, et al. Fucus vesiculosus: a nephrotoxic alga? Nephrol Dial Transplant 1998;13:526-7.

8. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2002. Available at: www.nap.edu/books/0309072794/html/.