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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.Photo of dried kelp

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.

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. However, the average laminaria-based supplement might contain large amounts of iodine that can cause hypothyroidism, hyperthyroidism, or exacerbate existing hyperthyroidism.  Also some supplements may contain arsenic.  There is insufficient information regarding kelp supplements to validate its safety.   

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.

Always consult with your 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. 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 breastfeeding 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 websites with general information on nutrition.