Iodine is a chemical element and an essential nutrient that the body requires to produce thyroid hormones. These hormones play a critical role in regulating protein synthesis, energy metabolism, and normal growth and development. If you consume too much iodine, it can overwhelm the thyroid gland, the organ in the front of your neck that produces thyroid hormones. Evidence suggests that kelp contains multiple times the amount of iodine you normally need.
Seaweed
Seaweed is a colloquial term for a group of multicellular marine algae that grow in nutrient-rich waters. Coastal cultures throughout the world, such as Japan, China and Vietnam, include seaweed as part of the diet. Kelp is a type of brown algae that encompasses many species. Because iodine is present in high concentrations within seawater, it passes over to the kelp during its lifespan.
Iodine Content
The Institute of Medicine has set the recommended dietary allowance of iodine in adult men and women at 150 mcg daily. By comparison, the tolerable upper limit is 1,100 mcg per day. People without pre-existing thyroid conditions may exceed this limit intermittently, but the thyroid gland can tolerate only so much iodine. In 2004, researchers from the University of South Carolina published a study in the journal "Thyroid" that found two species of pre-harvested Namibian kelp ranged in iodine content from 514 mcg per gram in sun-bleached blades to 6,571 mcg per gram in freshly cut juvenile blades. One type of kelp granules, made from a species known as Laminaria digitata, contained as much as 8,165 mcg per gram. However, some iodine may vaporize in humid storage conditions, so the iodine content of prepared food is difficult to estimate.
Consumer Warning
Recalls of seaweed due to iodine concentrations have not occurred, but in 2010, the Australian Medical Association issued a consumer warning that products containing seaweed may harbor dangerous levels of iodine. Kelp is present in many foods. Some companies use seaweed to make soy milk, for example. Seaweed can be particularly problematic for babies, who already receive high doses of iodine from breast milk.
Thyroid Disorders
High levels of iodine can have opposite effects. In many people, especially adults, the thyroid gland will respond by producing too much thyroid hormone. This is known as hyperthyroidism. In others, particularly babies, high levels of iodine can overwhelm the thyroid gland and cause a deficiency of thyroid hormone. This is known as hypothyroidism. Symptoms of the disease include fatigue, weight gain, enlargement of the thyroid gland and depression.
Member Comments