Bladderwrack
Fucus vesiculosus
A brown seaweed recognised in the EU as a traditional herbal medicine to help weight loss alongside a reduced-calorie diet. It can affect the thyroid.
Bladderwrack may interact with some medicines. If you take any medicine, read Interactions with medicines below and talk to your doctor or pharmacist before using it.
What is Bladderwrack?
- Plant family
- Fucaceae, the rockweed family of brown seaweeds
- Parts used
- The whole dried seaweed (thallus), powdered
- Genus
- Fucus
- Species
- vesiculosus
Also called
Fucus, Bladder Wrack, Rockweed
Traditionally used for
- Weight loss with a reduced-calorie diet (traditional)
Traditionally described as
Traditions that use it
European Folk Medicine
A traditional herbal medicine in the EU, used alongside a reduced-calorie diet to help weight loss.
Safety
Interactions with medicines
One person taking lithium for bipolar disorder developed an overactive thyroid while using bladderwrack.[1]
Who should avoid it
Not recommended for anyone under 18. Don't take it with other bladderwrack products, iodine supplements or thyroid medicines.[1]
Pregnancy
Its safety in pregnancy and breastfeeding hasn't been established, so it isn't recommended then.[1]
How much to use
Taking more than the recommended amount can change thyroid hormone levels. Too much may cause:
- Worse acne
- A pounding or fast heartbeat
- Trembling
- Changes in blood pressure
In three women, 700 or 1,400 mg a day for several weeks lengthened their menstrual cycles.[1]
What does the research say?
Traditional use
These are traditional uses, not proven treatments.
Bladderwrack is a brown seaweed. The European Medicines Agency recognises it as a traditional herbal medicine, based on long use rather than trials, to help overweight adults lose weight alongside a reduced-calorie diet, after a doctor has ruled out serious conditions.
- The usual dose is 130 mg of the powdered seaweed twice a day, 2 hours before meals
- If you haven't lost weight after 10 weeks, see a doctor or qualified practitioner
In short
Not for under-18s, in pregnancy or breastfeeding, or with iodine or thyroid medicines. Too much can affect the thyroid and heart rate.
Sources
- [1] Community herbal monograph on Fucus vesiculosus L., thallus (EMA/HMPC/313674/2012) — European Medicines Agency, Committee on Herbal Medicinal Products (HMPC)Government health agency
This information is educational and traditional in nature, and is not a substitute for professional medical advice.