Side effects of bladderwrack kelp

Written by shelley moore
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Fucus vesiculosus, a type of seaweed commonly called bladderwrack, has been used traditionally and in alternative medicine to treat a wide variety of health conditions. Research is lacking on its effectiveness, and many side effects are possible when taken as a supplement or consumed in large amounts.

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Bladderwrack kelp is available as a supplement in tablets, extract or capsules. It also can be eaten as a vegetable, for instance in salads and soups.


The U.S. National Institutes of Health (NIH) indicates the possibility of bladderwrack benefit for antibacterial, anti-fungal, anticoagulant and antioxidant properties. It also may lower blood sugar levels and suppress the growth of cancer cells. Clear scientific evidence is lacking, however.


Most negative effects from bladderwrack seem to result from the high iodine content or contamination with heavy metal, according to the National Institutes of Health (NIH).


Iodine may cause brassy taste sensations, increased salivation and upset stomach. High iodine content also can lead to thyroid disorders. The NIH notes that some bladderwrack users have reported severely worsening acne, a condition connected with dietary iodine.

Additional Effects

Chronic use of bladderwrack has a laxative effect. Abnormal bleeding and reduced blood platelets also have been reported. Reports of kidney and nerve damage appear related to heavy metal contamination, according to the NIH.


People taking anticoagulants, thyroid medications or medications for diabetes may not be able to safely consume bladderwrack kelp. Pregnant women should not take bladderwrack because of high iodine levels and the possibility of heavy metal contamination.

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