Iodine is an essential trace element, necessary primarily for the synthesis of thyroid hormones thyroxine (T4) and triiodothyronine (T3)[diagram]. Thyroid hormones regulate many important biochemical reactions, including protein synthesis and enzymatic activity, and are critical determinants of metabolic activity [1,2]. They are also required for proper skeletal and central nervous system development in fetuses and infants [1].

Dr. David Brownstein[3] says that its importance is even more[4]:

Iodine deficiency is the underlying problem responsible for the high rate of cancer (particularly breast, lung, prostate and ovary) as well as the high rate of autoimmune disorders we are seeing in this country.

To help you understand iodine's importance, its benefits are summarized in the next section.  

Health Benefits of Iodine

Optimal intakes of iodine can help:

• Prevent cretinism and dwarfism

  • An adequate iodine intake during pregnancy is essential for normal development of the fetus.

  • Based on multiple researches[10,11], it shows that pregnant women and infants are exceptionally vulnerable to iodine deficiency.

• Prevents mental retardation[5]

  • Even moderate deficiency, especially in pregnant women and infants, lowers intelligence by 10 to 15 I.Q. points.

  • Iodine deficiency has adverse effects in all stages of development but is most damaging to the developing brain.

• Prevent goiter— a swollen thyroid gland in the neck.

  • The thyroid enlarges in response to persistent stimulation by TSH (thyroid-stimulating hormone).

• Exhibit antitumoral effects

  • In thyroid and breast cancer, iodine treatments inhibit cell proliferation and induce apoptosis through a direct (mitochondria) and/or indirect effect (iodolipid generation)[6]. 

  • Several groups have reported that iodine exhibited antiproliferative and apoptotic effects in various cancer cells only if this element is supplemented as molecular iodine  I2  or as iodide (KI or NaI) to cells that are able to oxidize it with the enzyme thyroperoxidase[7].

  • Moderately high concentrations of iodine may reduce pathologies in several iodine-uptake tissues such as thyroid, mammary gland, intestine, and prostate[8,9].

• Prevent autoimmune disease

  • Prevalence of SLE (systemic lupus erythematosus) in hypothyroid patients is high compared to the general population, especially, as thyroiditis is very common in SLE.

• Regulate gene expression[15]

  • In target tissues, such as the liver and the brain, T3, the physiologically active thyroid hormone, can bind to thyroid receptors in the nuclei of cells and regulate gene expression. 

  • In target tissues, T4, the most abundant circulating thyroid hormone, can be converted to T3 by selenium-containing enzymes known as deiodinases.  So, that's why holistic physicians prescribe both iodine and selenium to treat their patients.

• Treat Fibrocystic Breast Disease[12]

  • The breasts and the thyroid are two of the body’s main storage sites for Iodine.  In a deficient or depleted state, these tissues become primed for illness including fibrocystic breast disease and breast cancer.

• Minimize radioactive iodine uptake from nuclear fallout[18]

  • By ingesting large amounts of non-radioactive iodine, radioactive iodine uptake by the thyroid gland can be minimized. 

    • The typical adult dose is one 130 mg tablet per 24 hours, supplying 100 mg (100,000 micrograms) iodine, as iodide ion. 

  • Iodine isotope's (i.e. Iodine-131) radiological half-life is eight days

• Regulate the body's metabolism, particularly its use of energy, fats, and protein.

Is More Better?

As described in [13], the prevalence of iodine deficiency is more than you thought.  However, high iodine intake can also cause unexpected health problems in a subset of individuals with pre-existing thyroid disorders. Although it is reported that excessive iodine does not cause thyroid antibody positivity, high intake can cause or worsen symptoms for people with previous thyroid autoimmunity or other underlying thyroid issues [16]. Transient hypothyroidism and iodine-induced goiter is common in Japan and can be reversed in most cases by restricting seaweed intake [17].

Based on a study published in Annals of Internal Medicine[20], too much thyroid hormone may also put older women at risk for bone fractures.  During the 4 years of the study, 48% of the women had a hip fracture and 56% had a spine fracture. Women whose TSH level indicated a high thyroid hormone level were three times more likely to have a hip fracture and four times more likely to have a spine fracture than were women with normal levels of TSH.

The key is to consume iodine in moderation, read [19] to find how much daily iodine intake is enough.

References

1. National Research Council, Committee to Assess the Health Implications of Perchlorate Ingestion. Health Implications of Perchlorate Ingestion. Washington, DC: The National Academies Press, 2005.

2. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001.

3. Dr. David Brownstein

4. 5 Signs you'll Get Cancer And 7 Smart Ways to Prevent It!

5. In Raising the World’s I.Q., the Secret’s in the Salt

6. Uptake and antitumoral effects of iodine and 6-iodolactone in differentiated and undifferentiated human prostate cancer cell lines. (PubMed.org)

7. Antineoplastic effect of iodine and iodide in dimethylbenz[a]anthracene-induced mammary tumors: association between lactoperoxidase and estrogen-adduct production. (PubMed.org)

8. Venturi S,  Donati FM,  Venturi A,  Venturi M,  Grossi L &  Guidi A  2000 Role of iodine in evolution and carcinogenesis of thyroid, breast and stomach.Advances in Clinical Pathology 4 11–17.

9. Aceves C &  Anguiano B  2009 Is iodine an antioxidant and antiproliferative agent for the mammary and prostate glands? In Comprehensive Handbook of Iodine. Nutritional, Endocrine and Pathological Aspects, pp 249–257. EdsPreedy VR, Burrow GN & Watson RR. Oxford, England: Academic Press.

10. Risk of suboptimal iodine intake in pregnant norwegian women (PubMed.org)

11. Iodine sources and iodine levels in pregnant women from an area without known iodine (PubMed.org)

12. Fibrocystic Breast Disease – How Iodine Supplementation Saved Me From Unnecessary Surgery (Plus A Book Review: Iodine Why You Need It and Why You Can’t Live Without It by David Brownstein, MD)

13. Could You Be Iodine Deficient?

14. Thyroid Hormone Synthesis (Wikipedia)

15. Iodine (Linus Pauling Institute)

16. Nagata K, Takasu N, Akamine H, Ohshiro C, Komiya I, Murakami K, Suzawa A, Nomura T: Urinary iodine and thyroid antibodies in Okinawa, Yamagata, Hyogo, and Nagano, Japan: the differences in iodine intake do not affect thyroid antibody positivity.

17. Tajiri J, Higashi K, Morita M, Umeda T, Sato T: Studies of hypothyroidism in patients with high iodine intake.  J Clin Endocrinol Metab 1986, 63:412-417.

18. Iodine (Wikipedia)

19. How Much Daily Iodine Intake Is Enough?

20. Too Much Thyroid Hormone Increases Risk for Bone Fractures

21. Study: Nuclear Plant Shutdown Results in 4,319 Fewer Cancer Cases

    • The most statistically significant reductions were in breast and thyroid cancers in women,

22. Happy Shiny Seaweed — Kelp: The Miracle Plant

23. Häggström, Mikael (2014). "Medical gallery of Mikael Häggström 2014". WikiJournal of Medicine 1 (2).