Bladder wrack
Bladder wrack
This information describes the common uses of Bladder wrack, how it works, and its possible side effects.

Common Name

Sea kelp, Brown kelp seaweed, Sea wrack, Marine oak

How It Works

Claims of beneficial effects of bladder wrack have not been confirmed in clinical studies.

Bladder wrack extract is rich in iodine and is claimed to stimulate thyroid activity to treat obesity. There is no evidence to support this. Women who took bladder wrack showed improvement in their menstrual symptoms. Topical application of a bladder wrack extract showed benefits for skin. Further studies are needed to confirm these effects.

Purported Uses

  • Menstrual abnormalities
    In a small study, women who took bladder wrack reported improvement in menstrual symptoms.
  • Skin care
    Results of a clinical trial showed that topical bladder wrack extract can improve the skin.
  • Weight loss
    This use is not supported by scientific evidence.
  • Hypothyroidism
    Bladder wrack is rich in iodine and has been used as a supplement for patients with hypothyroidism caused by iodine deficiency. However, this has not been studied in clinical trials and the dosage used is unclear.
  • Fatigue
    There are no clinical data to support this use.

Patient Warnings

Patients with thyroid disorder or hormonal-sensitive cancers should talk to their doctors before using bladder wrack.

Side Effects

  • Consumption of a slimming product containing 20 different herbs, bladder wrack being one of them, resulted in hemorrhagic cystitis (inflammation of the urinary bladder) in a 33-year-old woman. Symptoms resolved after discontinuing the product.

Special Point

Bladder wrack is often referred to as brown kelp but it should not be confused with “kelp,” which is another species of seaweed.