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Kelp (kun bu)

What is kelp? What is it used for?

Kelp is a type of seaweed found in coastal regions where the water is shallow enough for light to penetrate to the sea floor. It is the largest type of seaweed in the world, with some varieties growing to 30 meters or more in length.

Kelp beds usually grow in forests which are highly productive ecological systems similar to tropical rain forests. Like rain forests, they form canopies under which many other species live, including fish, snails, shrimps and sponges.

Although kelp has no medicinal properties, it is an important source of food for fish and other marine animals. For humans, it is a vital source of several minerals, including iodine (a vital ingredient involved in the creation of thyroid hormones), magnesium, calcium and iron.

How much kelp should I take?

While there is no recommended daily allowance for kelp, many practitioners in the U.S. suggest a maximum of 150 micrograms per day. Because of its high iodine content, however, daily kelp intake should be monitored closely.

What forms of kelp are available?

Although it can be eaten raw, many specialty stores and Asian markets prefer to sell dried kelp leaves, either individually or in bulk. Kelp is also available in capsule or tincture form. Trace elements of it are also found in many multivitamin supplements.

What can happen if I take too much kelp? Are there any interactions I should be aware of? What precautions should I take?

Several case studies have suggested that high kelp intake could provide too much iodine, thus interfering with the normal function of the thyroid gland. Patients with hyperthyroidism, or who are taking medication to combat hyperthyroidism, should avoid all supplements that contain kelp.


  • de Smet PA, Stricker BH, Wilderink F, Wiersinga WM. Hyperthyroidism during treatment with kelp tablets. Ned Tijdschr Geneeskd 1990;134:1058—9 [in Dutch].
  • Eliason BC. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J Am Board Fam Pract 1998;11:478—80.
  • Kim JY, Kim KR. Dietary iodine intake and urinary iodine excretion in patients with thyroid diseases. Yonsei Med J Feb 2000;41(1):22-8.
  • Kupper FC, Kloareg B, Guern J, Potin P. Oligoguluronates elicit an oxidative burst in the brown algal kelp laminaria digitata. Plant Physiol Jan 2001;125(1):278-291.
  • van Netten C, Hoption Cann SA, Morley DR, van Netten JP. Elemental and radioactive analysis of commercially available seaweed. Sci Total Environ Jun 2000;8:255(1-3):169-75.
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