Iodine is an essential mineral for the entire body and all of the endocrine glands, however it is so essential for the thyroid that the gland can preferentially take up iodine - so if there are low thyroid symptoms there may be low iodine too, (G9.1) or excess halides, (G9.2), excess nitrates, commonly used as preservatives in processed meats, (G9.6), or excess thiocyanate from cigarette smoke, first or secondhand, or cruciferous vegetables, which would be unlikely to be consumed in excess unless juicing large amounts of cruciferous vegetables such as kale, broccoli, cabbage, and cauliflower. (G9.7, G9.8)
Iodine is a mineral that is essential for metabolism due to its role in the thyroid gland and thyroid hormone, and it plays a role in the immune system. It may help protect against cancer and autism and other neurological risks in addition to protecting against congenital hypothyroidism in the newborn. Mothers need iodine for their entire body, not just a synthetic hormone replacement with no additional iodine being provided than might be found in a one-a-day supplement. The need for iodine is increased throughout pregnancy and during lactation and might worsen an underlying moderately low level of iodine into a level that causes hypothyroidism. The thyroid can preferentially use iodine when it is in limited supply because it is needed for thyroid hormone, however the mammary glands and all endocrine glands also need iodine. Thyroid hormone is needed throughout the body for energy production. Hypothyroidism can cause extreme tiredness, poor hair growth, feeling cold easily, and depression or apathy, and constipation.
It is important to have selenium along with iodine rich supplements or foods as the enzyme required to break down excess amounts of thyroid hormone needs selenium in order to function properly. Two Brazil nuts per day or 200 mcg is the recommended amount of selenium to consume per day. Selenium can build up to toxic amounts if over eaten on a very regular basis.
Iodine toxicity is also possible, symptoms might include a rapid heart rate, feeling restless, an odd metallic taste in the mouth might occur that could also be due to the body excreting halides: bromide, chloride, and fluoride. Iodine toxicity would only be likely to occur with long term use of high dose supplements or extensive use of topical iodine sanitizing cleansers. Other symptoms might include feeling like there is something stuck in the throat, feeling a need to cough something out; a nasal watery drip may occur that is thin and more like an occasional tear rather than normal mucous and blowing the nose doesn't help because it isn't "clogged" it is just dripping occasionally, weeping almost. I'm familiar because I read about the symptoms in animal research and many years later happened to notice that I likely had continued a high dose iodine supplement too long, and'or I wasn't taking the recommended selenium at the time.
The long term benefit though has been an absence of fibrocystic breast pain which had been an uncomfortable problem for several years before I started the iodine supplement protocol by Dr. Brownstein. He has a website with information available online and more detail is included in several books. See Iodine: Why You Need It, for more information about use of a high dose iodine supplement for a few weeks to help clear the body of any stored bromide, chloride and fluoride. (G9.3)
The iodine content in food can vary a lot because iodized salt may or may not be used in processed foods and it is not required to be listed as a nutrient on the nutrient portion of a US Nutrient Food Label so the food content wouldn't be tested consistently either. Look among the ingredients for iodized salt or iodized sea salt. If the word salt or sea salt is listed then the food may not have much iodine naturally. Foods grown near the ocean such as coconut tend to be good sources because soil near the ocean has a higher iodine content than soil farther inland, away from ocean air. Ocean water is rich in iodine and some is carried inland from the sea air. Seafood and seaweed is a good source but the amount in seaweed can vary significantly and may occasionally be excessive. Kelp and kombu are two types of seaweed that have been found to have variable amounts of iodine while nori and wakame have been found to have more consistent amounts. Some plants like rhubarb are good sources of iodine because they preferentially absorb it from the soil.
- Clinical resources regarding iodine: (G9.5).
- Continuing Education for dietitians:Unexpected Trends in Iodine Consumption — Interventions to Improve the Health of Women and Their Offspring (G9.9)