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Iodine and Breast Health

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Association of iodine deficiency and ductal cell abnormalities

  • Breast cancer arises from breast tissue that produces milk [lobular tissue] or tissue that is a conduit for the milk [ducts]
  • About 70% of all breast cancer is infiltrating ductal adenocarcinoma.
  • Iodine deficiency may lead to abnormal cell changes in the breast: “When lacking, the parenchyma in rodents and humans show atypia, dysplasia, and even neoplasia; in fact, breast tissues are more susceptible to carcinogen action28.”

  • “Mammary gland is embryogenetically derived from primitive iodide-concentrating ectoderm, and alveolar and ductular cells of the breast specialize in uptake and secretion of iodine in milk in order to supply offsprings with this important trace-element. Breast and thyroid share an important iodide-concentrating ability and an efficient peroxidase activity, which transfers electrons from iodide to the oxygen of hydrogen peroxide, forming iodoproteins and iodolipids, and so protects the cells from peroxidative damage. The mammary gland has only a temporary ability to concentrate iodides, almost exclusively during pregnancy and lactation, which are considered protective conditions against breast cancer.28
  • 60 – 80% of iodine is non-hormonal and located in extra-thyroidal tissues such as the breast, salivary glands and gastric mucosa, liver, ovaries and testes and some tumours29.
  • The breast can avidly concentrate iodides during pregnancy and lactation to form iodocompounds [iodoproteins and iodolipids]
  • Iodine adsorption during pregnancy and lactation occurs in the same ductal tissue where the majority of breast cancers arise as indicated above. Pregnancy and lactation are two factors known to have a protective effect against developing breast cancer.
  • Many studies have shown an association between thyroid disease and breast cancer. There is an abundance of TSH receptors in breast tissue and the possibility of thyroid autoantibodies having an effect on breast tissue as well.
    “These results indicate a significant association between breast cancer and autoimmune and non-autoimmune thyroid disorders.33
  • Studies of iodine supplementation in fibrocystic breast disease showed around 70% improvement especially with nonthyrotropic molecular iodine [Ghent et al 1993]
  • Although surrounded by controversy, a direct association has been found between thyroid enlargement and breast cancer31.

Important to ensure adequate intakes of iodine

  • When all is said and done about the association between iodine and breast cancer the important point that persists is that iodine deficiency is a common problem in many parts of the world and no researcher in their right mind would challenge the fact that suboptimal iodine deficiency can have a negative impact on human health in particular with regard to pregnancy and foetal brain development. It is important to have at least the recommended daily intake [RDI] of iodine with the Tolerable Upper Intake Level (UL) for Iodine being 1100 mcg [1.1 mg]

High intakes can be safe as seen in studies of Japanese consumption

  • It is important to note that the Japanese population has a very low incidence of breast cancer. The daily intake of iodine in some Japanese coastal regions where seaweed consumption is high, has been documented to be 50,000 to 80,000 mcg/day [50 mg to 80 mg]32.

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