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What Are the Side Effects of Fucus Vesiculosus?

author image Linda Tarr Kent
Linda Tarr Kent is a reporter and editor with more than 20 years experience at Gannett Company Inc., The McClatchy Company, Sound Publishing Inc., Mach Publishing, MomFit The Movement and other companies. Her area of expertise is health and fitness. She is a Bosu fitness and stand-up paddle surfing instructor. Kent holds a bachelor's degree in journalism from Washington State University.
What Are the Side Effects of Fucus Vesiculosus?
Bladderwrack seaweed among rocks Photo Credit: AndyRoland/iStock/Getty Images

Fucus vesiculosus is a seaweed. You might be more familiar with its common name, which is bladderwrack, according to Natural Standard. It is sometimes used as an herbal medicine, according to the National Institutes of Health (NIH). You may see it advertised as a treatment for thyroid issues, asthma, coughs, stomach problems, urinary diseases, as a way to prevent headaches, as a preventive measure for tumors or ulcers or as a weight loss aid. There is not enough research to recommend for or against any of these uses, advises NIH. Meanwhile, there are possible side effects of which you should be aware.

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Iodine and Heavy Metal Toxicity

Most of the side effects you might experience are related to Fucus vesiculosus's high iodine content, or to contamination of bladderwrack preparations by heavy metals or other substances, advises NIH. In fact, NIH advises that consuming bladderwrack is considered “potentially unsafe” due to potential contamination. Iodine toxicity can cause abnormal thyroid conditions. Bladderwrack theoretically can decrease or increase blood thyroid hormone levels. High iodine levels can also lead to acne-type skin lesions, stomach irritation, a brassy taste in your mouth, or increased salivation. Arsenic contamination of seaweed has led to nerve and kidney toxicity in some people. Contamination also can lead to abnormal bleeding and reduced blood platelet count.

Lower Blood Sugar Levels

Fucus vesiculosus extracts can lower blood sugar. The NIH urges caution for people who have hypoglycemia, diabetes, or who take herbs or drugs that affect blood-sugar levels. It’s best to have your serum glucose levels monitored by a doctor if taking bladderwrack, according to NIH.

Blood Thinning

There are potential blood-thinning, or anticoagulant, properties in bladderwrack. There are reports of autoimmune thrombocytopenic purpura in people consuming this seaweed, according to NIH. If you take blood thinners or other drugs that can increase risk for bleeding, or have a bleeding disorder, you need to be monitored by a doctor when taking Fucus vesiculosus, NIH advises.

Laxative Effect

The alginic acid in Fucus vesiculosus may cause a laxative effect, according to NIH. This effect most often is experienced with chronic use the seaweed. Combining bladderwrack with other laxatives may boost the effect of those laxatives.

Drug Interactions

If you take drugs for your thyroid, bladderwrack may interfere with their function due to its high iodine content, according to NIH. If you take lithium, take care. Using iodine-containing agents can alter thyroid function when taken along with this drug. Also be cautious if you take hormonal drugs, including birth control, because bladderwrack may interact with these.

Pregnancy Concerns

Due to lack of reliable scientific information on Fucus vesiculosus, you should avoid it if you are pregnant or breastfeeding, according to RX List. You need to be concerned about its high iodine levels and possible heavy metal contamination, according to NIH.

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