Also indexed as: Ascophyllum nodosum, Laminaria
digitata
Kelp is a sea vegetable that is a
concentrated source of minerals, including
iodine, potassium, magnesium, calcium, and iron. Kelp as a source of iodine assists in making
thyroid hormones, which are necessary for maintaining normal metabolism in all cells of the
body.
Where is it found?
Kelp can be one of several brown-colored seaweed species called Laminaria.
Kelp has been used in
connection with the following condition (refer to the individual
health concern for complete information):
| Science Ratings |
Health Concerns |
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Iodine deficiency
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Who is likely to be deficient?
People who avoid sea vegetables, as well as
dairy, seafood, processed food, and the salt shaker, can
become deficient in iodine. Iodine deficiency can cause low thyroid function, goiter, and cretinism. Although iodine deficiency is
now uncommon in Western societies, the U.S. population has shown a trend of significantly
decreasing iodine intake.
How much is usually taken?
Since the introduction of iodized salt, additional sources of iodine, such as kelp, are not necessary for most
people. However, kelp can be consumed as a source of other minerals. A report from Great
Britain indicated that the average kelp-based supplement contained 1,000 mcg of iodine (the
adult RDA in the United States is 150 mcg per day). It has been suggested that intakes above
2,000 mcg per day should be regarded as excessive or potentially harmful.1
Are there any side effects or interactions?
There have been several case reports of high intakes of kelp providing too much iodine and interfering with normal thyroid
function.2 3 4 5 6 People with thyroid
disease should check with a doctor before taking supplements that contain kelp.
At the time of writing, there were no well-known drug interactions
with kelp.
References:1. Wolff J. Iodide goiter and the pharmacologic effects of excess iodide.
Am J Med 1969;47:101–24.
2. Shilo S, Hirsch HJ. Iodine-induced hyperthyroidism in a patient with a
normal thyroid gland. Postgrad Med J 1986;62:661–2.
3. Ishizuki Y, Yamauchi K, Miura Y. [Transient thyrotoxicosis induced by
Japanese kombu]. Nippon Naibunpi Gakkai Zasshi 1989;65:91–8 [in Japanese].
4. Hartman AA. [Hyperthyroidism during administration of kelp tablets
(letter)]. Ned Tijdschr Geneeskd 1990;134:1373 [in Dutch].
5. de Smet PA, Stricker BH, Wilderink F, Wiersinga WM. [Hyperthyroidism
during treatment with kelp tablets]. Ned Tijdschr Geneeskd 1990;134:1058–9 [in
Dutch].
6. Eliason BC. Transient hyperthyroidism in a patient taking dietary
supplements containing kelp. J Am Board Fam Pract 1998;11:478–80.