Iodine is a trace element, meaning the body only needs it in small quantities. Humans require about 0.15 mg of iodine daily for oxygen transportation, energy processing and thyroid hormone production. Iodine deficiency in the United States is rare due to iodized salt; most iodine deficiencies occur in under-developed countries where iodine and iodized salt are expensive. A natural source of iodine is kelp, a sea vegetable that absorbs the mineral from ocean water. The discovery of kelp as a source of iodine in the 1700s, led to the treatment of goiter, or enlarged thyroid gland. Consult a qualified health care provider before taking kelp or iodine supplements.
Sources of Kelp
Dried and whole kelp can be found in many grocery stores, Asian markets and health-food stores. It is dried for use in supplements and available in tablet, capsule or powder form. Kelp is also marketed as spirulina or blue-green algae. The American Cancer Society recommends eating whole seaweed as opposed to taking supplements, since dried seaweed contains high amounts of nutrients that may be harmful.
Uses of Kelp
Kelp may have other uses aside from treating hypothyroidism. Japanese women have a lower incidence rate of breast cancer, and longer life expectancy after breast cancer, than American women. Higher seaweed consumption is one explanation for this phenomenon. The American Cancer Society reports that some forms of algae slow cancer growth in laboratory studies. In addition, high blood pressure treatment may include the use of seaweed, since it helps remove sodium from the bloodstream.
Just as a deficiency of iodine can disrupt production of thyroid hormones, too much iodine can block the production of hormones in the thyroid gland and also cause hypothyroidism. In Japan, where high amounts of seaweed are consumed, some people exhibit this type of blockage causing diet-induced goiter; this condition ceases when seaweed consumption is reduced. An excess of iodine can also lead to Grave's disease, thyroid cancer and toxic levels of thyroid hormones. The Food and Drug Administration recommends a maximum of 225 mcg of kelp per day. Symptoms of iodine poisoning include abdominal pain, diarrhea, fever, mouth tastes of metal, lack of urination, seizures, shortness of breath, thirst or vomiting. MedlinePlus recommends immediate medical treatment.
Read labels carefully. A UC Davis study released in April 2007 found that kelp naturally contains organic arsenic and may cause arsenic poisoning when exceeding the recommended amount. Researchers evaluated nine different kelp products and found that eight contained unacceptable levels. Iodine intake may also interact with other medications containing potassium iodide such as lithium or warfarin. Safety during pregnancy has not been established. Kelp use can cause skin to turn yellow, or look jaundiced, due to its high amount of carotenoids.
- “Biology Concepts and Connections”; Neil A. Campbell, et al; 2008
- “Environmental Health Perspective”; Safe Use of Herbal Kelp Supplements; Michael McGuffin and Steven Dentali; December 2007
- MedlinePlus: Iodine Poisoning
- University of Maryland Medical Center: Iodine
- Drugs.com: Complete Seaweed
- American Cancer Society: Sea Vegetables
- EurekAlert: UC Davis Study Finds High Arsenic Levels in Herbal Kelp Supplements