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The Health Benefits & Side Effects of Kelp

author image Owen Bond
Owen Bond began writing professionally in 1997. Bond wrote and published a monthly nutritional newsletter for six years while working in Brisbane, Australia as an accredited nutritionalist. Some of his articles were published in the "Brisbane Courier-Mail" newspaper. He received a Master of Science in nutrition from the University of Saskatchewan.
The Health Benefits & Side Effects of Kelp
A bowl of sea kelp on a rustic table. Photo Credit: tycoon751/iStock/Getty Images

Kelp is a type of seaweed, or algae, commonly eaten in Asian countries, such as Japan and China. Kelp is found mainly in kelp forests within shallow bodies of saltwater and can grow up to half a meter a day, ultimately reaching heights of 30 to 80 meters. Kelp is considered a super-food because of all the nutrients it contains. Eating large amounts of it can cause side effects.

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Vitamins and Minerals

Kelp contains many vitamins, especially B vitamins, which are essential for cellular metabolism and providing your body with energy. It also contains vitamins C and E, which are both strong antioxidants and promote blood vessel health. Minerals, such as calcium, boron and magnesium are plentiful in kelp; they are necessary for strong bones and normal muscle function.

Sodium Alginate

Kelp, like other seaweeds, is rich in sodium alginate, which is an element effective at protecting the body from radiation and removing it. According to a 1964 study published in the “Canadian Medical Association Journal,” sodium alginate derived from kelp reduced radioactive strontium absorption in the intestines by 50 to 80 percent. Specifically, sodium alginate allows calcium to be absorbed through the intestinal wall while binding most of the strontium, which is excreted from the body.


Seaweed is also a rich source of iodine, which is a crucial nutrient for the thyroid. A deficiency in iodine leads to goiter, or swelling of the thyroid, and metabolism disruption. Iodine is the main element used to synthesize the thyroid hormones thyroxine and triiodothyronine. The thyroid gland absorbs iodide from the bloodstream to make its hormones, although the process is regulated by the pituitary gland. Consuming iodine from plants like kelp also helps reduce the effects of radiation exposure.


Chlorophyll is used by plants to convert sunlight into energy, and it contains many nutrients, including antioxidants and amino acids. Chlorophyll is also similar in composition to human blood, so consumption of it can stimulate red blood cell production, which can increase oxygenation around the body. Kelp contains plentiful amounts of chlorophyll.

Side Effects

Kelp contains a large amount of iodine, which can cause side effects. Although some iodine is essential for thyroid function, ingesting too much of it can negatively affect thyroid function, causing hypo- or hyper-thyroidism. Many thyroid specialists suggest that adults consume about 150 micrograms of iodine daily, although that is well below the level that could cause side effects. Table salt is iodized, so you should balance your kelp consumption against your salt intake.

Kelp might also contain arsenic, and consuming large amounts of kelp supplements might lead to arsenic poisoning.

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  • “Canadian Medical Association Journal”; Studies on Inhibition of Intestinal Absorption of Radioactive Strontium; S.C. Skoryna et al.; June 1964
  • “Biochemistry of Human Nutrition”; George Gropper; 2000
  • "The New Encyclopedia of Vitamins, Minerals, Supplements, and Herbs"; Nicola Reavley; 1999
  • “Advanced Nutrition: Macronutrients, Micronutrients, and Metabolism”; Carolyn D. Berdanier; 2009
  • NYU Langone Medical Center: Kelp
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