Bladderwrack: Health Benefits, How To Use, And Side Effects

Medically Reviewed by Olga Afonsky, MS, LDN
Written by Aparna Mallampalli, BEd (Biological Sciences), MSc (Microbiology), Diploma In Nutrition

Bladderwrack is popular for its medicinal properties. It is commonly used in traditional medicine as a supplement. The health benefits of bladderwrack are evident with its impressive nutritional profile. This seaweed is known to help manage several health conditions. But what does science say? Does bladderwrack have any side effects? Continue reading to understand.

What Is Bladderwrack?

Bladderwrack is a seaweed that grows on the coasts of the North Sea, Western Baltic Sea, and the Atlantic and Pacific Oceans. It is commonly known as black tang or brown seaweed. Many consume bladderwrack for its medicinal properties. It is especially used for managing thyroid disorders as it contains iodine, an essential component for maintaining normal thyroid function (1).

Continue reading to know about the nutritional value of bladderwrack.

Bladderwrack Nutrition Profile

A hundred grams of dried bladderwrack powder contains (2):

Protein12.99 g
Lipid3.75 g
Ash20.71 g
Calcium1160.27 ± 23.10 mg
Iron18.99 ± 0.32 mg
Potassium3745.05 ± 36.01 mg
Manganese8.28 ± 1.07 mg
Sodium2187.51 ± 36.90 mg
Amino Acids11.90 g
Magnesium1.96 mg – 8.28 mg

Bladderwrack is chock-full of nutrients and has multiple health benefits. Let’s understand how it can keep you healthy.

Bladderwrack Health Benefits

1. Improves Gastrointestinal Function

Bladderwrack contains high levels of dietary fiber, which promotes gastrointestinal health. Dietary fiber helps regulate the intestinal flow and also stimulates the growth of gut-friendly microbiota.

2. Helps Manage Diabetes

Bladderwrack contains fucoidans, bioactive compounds with potent anti-diabetic properties. They can reduce glucose absorption into the bloodstream, increase serum insulin levels, and help manage diabetes. Animal studies found that oral intake of bladderwrack reduced fasting blood glucose levels.

3. Has Anticoagulant Properties

The fucoidans in bladderwrack make it an excellent anticoagulant. Animal studies found that fucoidans could mimic the action of heparin, a potent anticoagulant. This may reduce the risk of ischemic stroke by minimizing blood clotting tendency in people with a history of hypertension and diabetes. However, the exact mechanism of how it works is not yet clear and needs further research.

4. Has Antitumor Properties

Fucoidans have antitumor properties and were found to significantly inhibit the number of metastases in lung carcinoma (in mice studies) and exhibit anticancer activities (3).

5. Antiviral Properties

The fucoidans in bladderwrack have a capacity to inhibit poliovirus III, adenovirus III, ECHO6 virus, herpes simplex virus (HSV), cytomegalovirus (CMV), and dengue virus (3). However, the exact mechanism remains unclear.

If you are wondering how to include bladderwrack in your diet, read the next section.

How To Take Bladderwrack And Recommended Dosage

Seaweeds, in general, have a fishy smell, which can be unpleasant for a few when consumed as they are or in powdered form. That is why bladderwrack and other seaweed supplements are available in capsules.

It is best to consult a doctor to determine the ideal dosage (usually, it does not exceed three capsules), depending on your health condition and nutritional requirements, as unregulated intake may cause side effects.

Side Effects Of Bladderwrack

Bladderwrack is possibly safe when taken in small amounts. But anecdotal evidence suggests that excess intake may cause a few side effects like:

  • Nausea And Vomiting: Its unpleasant taste and odor may make you nauseous and cause vomiting.
  • Diarrhea: A few people reported experiencing diarrhea and sticky stools after taking bladderwrack supplements. This might be due to bladderwrack’s nutrient-dense nature. You may also experience dehydration due to diarrhea. Hence, consume adequate amounts of fluids to combat this.
  • Bloating: Excess consumption of bladderwrack may cause bloating and gastric pain, which may be due to the high fiber content. Stay hydrated to minimize this side effect.
  • Tingling Sensation In The Throat: If you are allergic to bladderwrack, it may cause itching and tingling sensation in the throat.
  • May Aggravate Acne: Excess consumption of bladderwrack may worsen acne due to its high iodine content. However, there is no research to prove the exact mechanism.

If you experience any of the symptoms, stop consuming bladderwrack supplements. If the effects persist for over three days, consult a doctor immediately.

Bladderwrack’s benefits can be attributed to its nutritional content. When included as a part of your regular diet, bladderwrack can promote gastrointestinal function, help in managing diabetes, and exhibit anti-coagulant properties. It also has anti-tumor and anti-viral properties. Bladderwrack is generally taken in the form of capsules. Although it is generally considered safe, it can trigger nausea, vomiting, diarrhea, bloating, a tingling sensation in the throat, and aggravate acne if taken in excess amounts. Hence, caution is advised when consuming it. However, you can take bladderwrack or its supplements with medical advice to promote your overall health.

Frequently Asked Questions

Can I take bladderwrack every day?

Yes, you can take bladderwrack every day only if advised by the doctor.

Who should not take bladderwrack?

Bladderwrack is safe when taken as per the doctor’s advice. However, avoid it if you are allergic to seaweeds and have asthma. Also, avoid consuming it if you are pregnant or breastfeeding.

Can bladderwrack cause high blood pressure?

Excessive iodine and sodium intake may cause high blood pressure. Since bladderwrack contains iodine, excess intake may increase blood pressure levels.

Is bladderwrack good for skin?

Bladderwrack is rich in nutrients and antioxidants that help maintain overall health and your skin health. Moreover, antioxidants can reduce oxidative damage, one of the main causes of premature aging.

Key Takeaways

  • Bladderwrack, also known as brown seaweed, is rich in protein, calcium, iron, and magnesium.
  • Consuming bladderwrack may promote digestion, reduce blood glucose levels, and minimize blood clotting in individuals with high blood pressure and diabetes.
  • However, excess consumption of bladderwrack may result in side effects such as nausea and vomiting.


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  1. Promoting Healthy Thyroid Function with Iodine Bladderwrack Guggul and Iris
  2. Proximate Composition and Nutritional Value of Three Macroalgae: Ascophyllum nodosum Fucus vesiculosus and Bifurcaria bifurcata
  3. Phycochemical Constituents and Biological Activities of Fucus spp.
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Olga Afonsky

(MS, LDN )
Olga Afonsky is a board-certified clinical nutritionist and works in Washington DC. She loves supporting people in their weight loss... more