Iodine promotes a healthy thyroid gland. Iodine deficiency leads to an enlarged thyroid, known as goiter, which compromises its function. Iodine is a central component within thyroxine and triiodothyronine, the T4 and T3 thyroid hormones that regulate cellular metabolism and energy production. Kelp is a rich source of iodine and often prevents goiter and hypothyroidism.
Kelp
Kelp is a multi-cellular algae, better known as a seaweed, that is consumed raw, cooked or as a supplement. Kelp is a rich source of many nutrients, especially iodine, and considered by some to be a "superfood." In addition to iodine, kelp is rich in folate and other B-vitamins, but is also a good source of chlorophyll, amino acids, vitamins C and E, magnesium, calcium, iron and phosphorus, according to the "American Dietetic Association Complete Food and Nutrition Guide." Kelp is of marine origin, as freshwater seaweeds are usually toxic to people.
Iodine Content of Kelp
Iodine levels in seaweeds vary and depend on the type. Kelp contains the highest amount of iodine of any seaweed, with some species having 8,165 mcg per gram. Most kelp, such as kombu, has about 2,500 mcg of iodine per gram, the majority of it in the form of iodide. Other common seaweeds have much less iodine content. Nori contains only 16 mcg of iodine per gram, whereas hijiki contains 629 mcg. In terms of processed supplements, iodine content in 17 different brands ranged dramatically from 45 to 57,000 mcg per tablet or capsule, according to collective research cited in "Biochemistry of Human Nutrition."
Recommended Iodine Intake
Some dietary iodine is essential for healthy thyroid function, which is why table salt in the United States has been iodized for many decades. The recommended daily intake for iodine is 150 mcg daily for people 4 years and older. Taking a great deal more than this for weeks or months can upset the balance of the thyroid gland, in addition to causing mild sickness, such as nausea. Iodine content in kelp is reduced by storage and cooking.
Iodine and Radiation Protection
The rich iodine content within kelp protects the thyroid from radiation. Specifically, if iodine levels are low during exposure to radiation, then radioactive iodine-131 will be absorbed instead and accumulate in the thyroid, leading to injury, mutation and cancer, according to "Human Biochemistry and Disease." In many hospitals in post-World War II Japan, patients exposed to nuclear radiation were fed diets rich in kelp to minimize damage to their thyroid glands.
Iodine Deficiency Symptoms
Chronic iodine deficiency eventually results in hypothyroidism and reduced hormone production, leading to profound fatigue, lethargy, weight gain, dry skin, sensitivity to cold and depression.
References
- "American Dietetic Association Complete Food and Nutrition Guide"; American Dietetic Association; 2006
- "Advanced Nutrition: Macronutrients, Micronutrients, and Metabolism"; Carolyn D. Berdanier; 2009
- "Biochemistry of Human Nutrition"; George Gropper; 2000
- "Nutrition and Public Health"; Sari Edelstein; 2006
- "Human Biochemistry and Disease"; Gerald Litwack; 2008
- "Harrison's Principles of Internal Medicine"; A. Fauci et al.; 2008
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