Botanical Name(s):

True kelps belong to the genus laminaria, family Laminariaceae. Giant kelps belong to the genus macrocystis, family Lessoniaceae. Bladder kelps belong to the genus nereocystis, family Lessoniaceae.

Other Name(s):


General Description:

Kelp is a common name for leafy algae or seaweed that is used as a food staple among Japanese people and other island and coastal cultures. It is a natural source of iodine and trace minerals.

Kelp needs sunlight as an energy source. It also needs a hard surface (not sand) on which to grow. Kelp growth is typically rapid, and giant kelp is one of the world's fastest growing plants, growing as much as 300 feet (100 m) in a single year.

Kelp contains iodine, which provides the trace element for incorporation into thyroid hormone. Proper iodine intake can prevent a goiter.

Medically Valid Uses:

Besides its use as a food staple, kelp is also used to produce a group of compounds called alginates such as carrageenan. Alginates are used in the food industry to stabilize and improve the textures of foods such as ice cream and chocolate milk. The thick smooth feel of chocolate milk is produced by adding alginates. Alginates are also used in toothpaste and cosmetics.

Kelp products are also used as soil conditioners adding organic material to poor soils.

As a health supplement kelp is used as a natural source of iodine in the diet.

Unsubstantiated Claims:

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Claims about kelp, generally unsubstantiated, suggest that it improves sensory receptors, promotes healthy nails and blood vessels, aids digestion, alleviates constipation, minimizes hair loss and helps with weight management. Kelp is also claimed to support treatment of gastrointestinal ulcers and decrease risk of breast cancer.

Dosing Format:

Kelp is available in powder and capsule form. Follow packaging instructions for the correct dose.

One should ALWAYS consult with his or her physician before beginning any type of herbal therapy.

Side Effects, Toxicity and Interactions:

Both hyperthyroidism (excessively increased thyroid function) and hypothyroidism (decreased thyroid function) have been linked to excessive kelp intake, due to its concentration of iodine. Many of these studies are reported from Japan, where kelp is part of the daily diet. However, abnormal thyroid function has also been linked directly to excessive ingestion of kelp supplements.

Kelp may contain metals that are detrimental to humans. Chronic ingestion of kelps taken from areas of contaminated ocean water may increase levels of cadmium, lead, aluminum, and possibly other heavy metals.

Women who are pregnant or breast-feeding should not use kelp supplements.

Kelp should not be taken when people are being actively treated for thyroid disease. In addition, kelp should not be used in conjunction with newer classes of antiarrhythmia heart medications, which contain large amounts of iodine.

Kelp supplements should probably be stopped one month before any X-ray studies that require contrast media and not resumed until the contrast media has cleared the system.

Additional Information:

Click here for a list of reputable Web sites with general information on nutrition.


  1. Konno N, Makita H, Yuri K, Iizuka N & Kawasaki K. Association between dietary iodine intake and prevalence of subclinical hypothyroidism in the coastal regions of Japan. J Clin Endocrinol Metab. 1994;78(2):393-7.

  2. Lee SM, Lewis J, Buss DH, Holcombe GD & Lawrance PR. Iodine in British foods and diets. Br J Nutr. 1994;72(3):435-46.

  3. Eliason BC. Transient hyperthyroidism in a patient taking dietary supplements containing kelp. J Am Board Fam Pract. 1998;11(6):478-80.

  4. Henzen C, Buess M, Brander L. [Iodine-induced hyperthyroidism (iodine-induced Basedow's disease): a current disease picture]. Schweiz Med Wochenschr. 1999;129(17):658-64.

  5. Walkiw O, Douglas DE. Health food supplements prepared from kelp--a source of elevated urinary arsenic. Clin Toxicol. 1975;8(3):325-31.

  6. Teas J. The dietary intake of Laminaria, a brown seaweed, and breast cancer prevention. Nutr Cancer. 1983;4(3):217-22.

  7. Chan HM, Kim C, Khoday K, Receveur O, Kuhnlein HV. Assessment of dietary exposure to trace metals in Baffin Inuit food. Environ Health Perspect. 1995;103(7-8):740-6.

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