Most of the Earth’s iodine is in the ocean. There is little iodine in soil and that is tightly bound. Vegetables are poor sources of iodine. Iodine deficiency is the most common endocrine disease and the most preventable form of mental retardation.
Serious fetal problems can occur due to maternal iodine deficiency, including hearing loss, learning problems, mental deficiency and demyelinization. Signs of low iodine in the mother are low thyroxine, high thyroid stimulating hormone (TSH) and enlarged thyroid (goiter.) Iodine deficiency can cause spontaneous abortion or stillbirth. Good iodine levels are important in breast milk for normal infant neurologic development.
Low iodine increases the risk of thyroid cancer since low iodine results in an increased uptake of radioactive iodine. Iodine deficiency appears to be the cause of autoimmune thyroid disease. By geographical studies, iodine deficiency seems to increase the risk of prostate, endometrial, ovarian and breast cancers.
North American population studies show that iodine consumption has dropped since the 1970’s, especially in women of childbearing age. Iodine insufficiency is diagnosed when urine levels of iodine are below 100 mcg/L. Fifteen percent of childbearing age women had urinary iodine levels below 50 mcg/L in 2001-2002 (moderate to severe iodine deficiency.) “The U.S. recommended daily intake (RDI) for dietary iodine is 150 mcg for adults, 220 mcg for pregnancy, and 270 mcg during lactation.” The upper limit of recommended iodine dose is 1,000 mcg. Higher doses may increase underlying thyroid disease and may increase the risk of autoimmune thyroid disease.
Japanese people consume much more iodine than do Americans, especially in seaweed. The Japanese people consume 5-14 times as much iodine as the upper safety limit in the U.S., 1000 mcg (1 mg,) and they suffer no problems because of it. Japanese women who eat the traditional high iodine, seaweed diet have low risk of benign or malignant breast disease. High iodine diets seem to protect breast and thyroid tissues. Japanese women have very low rates of breast cancer, compared to women in the United States, possibly, because Japanese women consume so much oral iodine. Japanese women who move to the United States and adopt a Western diet have rates of breast cancer similar to non-Japanese women in the U.S.
Iodine is used to form various thyroid hormones. Little is known about iodine beyond thyroid and breast functions. Iodine appears to have antioxidant functions similar to vitamin C. This would explain the benefit of seaweed baths to treat diseases, including thyroid disease, eye diseases and arteriosclerosis. The adequacy of dietary iodine can be tested by a urine sample. Mild deficiency is 50-99 mcg/L and severe deficiency is below 20 mcg/L.
Breast tissue concentrates iodine. Human milk has 4 times as much iodine as thyroid tissue does. Molecular iodine is the active form in breast tissue and is beneficial in fibrocystic disease. Iodide generates molecular iodine when it enters stomach acid.
Animal and human studies show that iodine-deficiency creates cellular changes, including carcinogenesis. Iodine supplements can shrink breast tumors in animals when given with progesterone. There seems to be a relationship between iodine and cancer growth.
Perchlorate is a product of jet fuel production. Perchlorate is in groundwater in much of the western U.S. Perchlorate is concentrated in human milk. Perchlorate competes for uptake with iodide and lowers T-3 and T-4 blood levels. Patients with perchlorate elevations have elevations of TSH and reduced T-4.
Selenium contributes to the metabolism of iodine by production of selenium enzymes. Coexisting deficiencies of selenium and iodine can increase TSH levels and can contribute to goiter growth.
CONCLUSION: Iodine is essential to breast and thyroid health. It is needed for fetal and infant neurological growth. Some environmental chemicals interfere with iodine utilization. Iodine is beneficial in treatment of problems of breast and thyroid. Co-supplementation with selenium is sometimes necessary.
NOTE: Thyroid cancer increased following the Chernobyl Accident. Read an article about the nutrient treatment of thyroid cancer. Read a review of thyroid cancer information and relation to iodine levels.
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PMID: 18590348.
Summary #387.
