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Taking Sea Kelp Supplements

author image Bonnie Singleton
Bonnie Singleton has been writing professionally since 1996. She has written for various newspapers and magazines including "The Washington Times" and "Woman's World." She also wrote for the BBC-TV news magazine "From Washington" and worked for Discovery Channel online for more than a decade. Singleton holds a master's degree in musicology from Florida State University and is a member of the American Independent Writers.
Taking Sea Kelp Supplements
A kelp forest. Photo Credit KGrif/iStock/Getty Images

Kelp belongs to a family of large seaweed plants used as food in Asia and other parts of the world. Packed with vitamins and minerals, kelp is also available as dietary supplements. The nutrients in kelp may, indeed, be good for your overall health. But don't rush out to buy the supplements. If you have thyroid problems, if you're taking an anti-coagulant medication or if you're keeping an eye on your sodium, you should probably steer clear of these supplements. Further, some supplements have worrisome levels of arsenic.


Kelp is a term often used to describe any form of sea vegetable. But it is actually several species of large, brown seaweeds that tend to grow in underwater forests. The kelp family includes the arame, bladderwrack, kombu and wakame varieties. Kelp supplements are often found in powdered and flake form, as well as in capsules and liquid drops.


Kelp includes the important minerals calcium, potassium, magnesium and iron, as well as trace minerals such as manganese, copper, zinc and chromium. Kelp also has vitamins A, C, E, B-1, B-2, B-6 and B-12, as well as a substance called ergesterol that converts to vitamin D in the body. In addition, it is a rich source of vegetable protein and iodine.

Health Benefits

Kelp contains algin, a compound that acts as a laxative, and fucans, which are inflammation fighters. Phytonutrients in kelp can inhibit the growth of cancerous tumors. A study at the University of California, Berkeley, which was published in the "Journal of Nutrition" found that kelp may reduce the risk of developing hormone-dependent cancers. Wakame kelp has demonstrated the ability to lower blood pressure, according to a study published in the “Journal of Nutritional Biochemistry” in 2000. According to research presented at the national meeting of the American Chemical Society in 2006, wakame has also been found to promote weight loss and have significant anti-diabetes effects.

Side Effects

The main concern with kelp supplements is the amount of iodine, which can affect your thyroid function. This could be especially problematic if you have thyroid disease. Kelp also has blood-thinning properties and may increase your risk of bleeding if you are taking anti-coagulants. Kelp has high amounts of sodium that can be a concern for those with high blood pressure. A few reports of allergies and stomach upset from kelp supplements have also been reported.


The iodine content of 17 different kelp supplements was found to range from 45 mcg to 57,000 mcg in a study published in 1988 in the journal “Human Additives and Contaminants.” The recommended daily intake for iodine is only 150 mcg. A University of California, Davis, study also found that eight of nine over-the-counter kelp products had higher than acceptable arsenic levels. Author and nutrition expert Dr. Ray Sahelian recommends using kelp supplements only occasionally.

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