Are Kelp & Seaweed High in Iodine?

Kelp and seaweed are very nutritious foods. Although their nutritional content varies, these foods can contain a variety of vitamins and minerals, including vitamins A and C, calcium, vitamin B-12, manganese, iron, zinc, and selenium. However, they are best-known for being one of the few foods with a naturally high iodine content.

Iodine Content

One gram of seaweed can contain anywhere from 16 mcg to 2,984 mcg of iodine, which is 11 percent to 1,989 percent of the daily value for iodine. Kelp contains an average of 1,500 mcg to 2,500 mcg of iodine. Brown algae have higher iodine content than either red or green algae, according to the Institute for Traditional Medicine.

Iodine Deficiency

Iodine deficiency can cause hypothyroidism or goiter, an enlarged thyroid. In children, it can cause cretinism, a form of mental retardation, or lower than average intelligence. Consuming 150 mcg of iodine per day can prevent iodine deficiency in adults. Vegetarians, pregnant women, people on low-salt diets and people who consume large amounts of foods that are considered goitrogens, including cauliflower, broccoli, cabbage and cassava, are at higher risk for iodine deficiency.

Iodine Toxicity

Consuming too much iodine can also be problematic. Since some seaweeds are high in iodine, consuming too much can lead to iodine toxicity and hyperthyroidism. Excess iodine consumption produces similar symptoms to iodine deficiencies. The safe upper limit for iodine is 1,100 mcg per day. Doses much higher than this can cause symptoms including abdominal pain, burning in the mouth, nausea, fever, diarrhea, vomiting, weak pulse and coma.

Considerations

Both iodine deficiency and iodine toxicity are rare in the United States. The iodine levels in seaweed and kelp can vary a lot, so you might not want to rely solely on them to meet your iodine needs. Eating a variety of foods, without consuming large amounts of any one food, will help you get sufficient iodine in your diet without consuming too much.

References

• MedlinePlus: Iodine in Diet; Linda Vorvick, M.D.; March 7, 2009
• Office of Dietary Supplements: Iodine
• "Journal of General Internal Medicine"; Iodine-Induced Thyrotoxicosis After Ingestion of Kelp-Containing Tea; Karsten Müssig, M.D., et al.; June 2006
• Linus Pauling Institute: Iodine; Jane Higdon, Ph.D., et al.; March 2010
• Institute for Traditional Medicine: The Nutritional and Medicinal Value of Seaweeds Used in Chinese Medicine; Subhuti Dharmananda, Ph.D.; December 2002