Thyroid Health: The Importance of Iodine by Maria "Adi" Benito-Herrero, MD
Updated: Nov 14, 2019
Thyroid health has been my passion since starting my integrative endocrine practice. Integrative medicine relies on the innate healing capacity of the human body. It uses an all-encompassing approach to health through nutrition, mind-body tools, botanicals and prescription medicines; using each of them when appropriate. Many of my patients reach out to me because they have been diagnosed with thyroid disorders. I enjoy educating my patients and the community at large on the role that particular nutrients play in thyroid health and how to obtain those nutrients safely and effectively. The thyroid gland is located at the base of our neck. It produces thyroid hormones, which are then carried to all the tissues and organs in our body. Thyroid hormones oversee our metabolism, our growth and how cells differentiate. They increase basal metabolism (heat production), increase our heart rate, stimulate fat mobilization, increase disposal of glucose (sugar) to our cells, and allow for normal growth, brain function and reproduction.
When our bodies do not have enough thyroid hormones to carry out these functions, we develop a state of low thyroid hormone—or hypothyroidism. Symptoms of hypothyroidism include dry skin, puffy eyes, poor memory, slow thinking, weak muscles, muscle cramps, fatigue, cold intolerance, deep and hoarse voice, and constipation. Hypothyroidism is most often caused by an autoimmune disease (Hashimoto’s thyroiditis), however, nutritional deficiencies can also lead to insufficient and inadequate thyroid hormone production.
The thyroid gland makes two hormones: thyroxine, also called T4, and triiodothyronine, also called T3. Our thyroid gland secretes these thyroid hormones (mostly T4) into the bloodstream and our cells convert T4 to T3. T3 is the active hormone and is responsible for the necessary thyroid functions. When our body is sick, under stress or lacking certain nutrients, our cells have a harder time converting T4 to T3. Although this is not a thyroid condition per se, thyroid blood tests might be abnormal.
Nutrients optimize our thyroid function Iodine is the primary nutrient for optimal thyroid production and function. Other important nutrients, which will be discussed in next week’s post, include tyrosine, selenium, iron, vitamin A and zinc.
Thyroid hormones are made from iodine. Since iodine is such an essential nutrient, we must ensure we get enough through our diet or in a supplement. When our bodies lack iodine, we cannot make enough thyroid hormones. Although the United States is still considered iodine sufficient, there are indicators that certain groups—such as vegetarians and vegans—are at risk for iodine deficiency.
How much iodine do we need? This depends on age, gender and reproductive status. The Institute of Medicine recommends the following daily amounts:
Iodine in food Iodine is found naturally in all marine fish and in foods grown in iodine-rich soils. The iodine content in most foods (not of marine origin) is low and the amount available depends greatly on the iodine content of the soil and how much irrigation and fertilizers are in use. In the United States, iodine is added (enriched) to most table salt; be sure the label states “iodized.” Of note, sea salt is not naturally rich in iodine. Other than marine fish/seaweeds or iodized salt, major sources of dietary iodine in the United States include egg yolks, milk and milk products and some breads. The USDA (U.S. Department of Agriculture) does not mandate that processed foods be labeled for iodine content, so it is difficult to know whether iodine is present in them and, if so, in what amount. The salt added to most processed foods is not likely to be iodized because the food industry thinks iodine imparts an unacceptable taste. We face a real challenge in getting enough iodine through our food. Our decreased fish consumption—thanks to concerns about contamination, use of salts that do not contain iodine and our increased consumption of processed foods—all combine to make it difficult for us to get enough iodine through our diets.
To increase iodine in your diet to ensure optimal thyroid hormone levels, eat:
½ teaspoon iodized salt per day, or
Saltwater fish or seafood, at least twice per week, or
Seaweed: choose Nori (at least one sheet per day), dulse (1/2 teaspoon per day) or wakame (2 tablespoons per day). These three seaweeds are safe for consumption daily or a few times per week. When cooked, seaweeds will lose some of their iodine, so although they might contain large amounts of iodine when raw (such as kombu), once cooked, their iodine content is reduced, or
1 cup of milk, twice each day
As a guide, if your diet (or your children’s diet) does not contain items in the above list, you might want to consider taking a multivitamin with iodine.
Health consequences of iodine deficiency include the following:
In pregnant women and their babies, lack of iodine has been linked to pregnancy loss, premature babies and mild neurocognitive defects. When severe, babies can develop a condition known as cretinism (babies are born hypothyroid because of a deep lack of iodine while in utero). Once it develops, cretinism cannot be corrected. It is not common in the Western world.
When the deficiency of iodine is mild or moderate during pregnancy there is a higher incidence of ADHD (Attention Deficit Hyperactivity Disorder) and lower IQ in the babies. Mothers and babies can develop a goiter (a large thyroid gland).
In school-age children, learning disabilities, poor growth and thyroid gland enlargement can be seen.
In adults, hypothyroidism and nodules develop.
In large population studies, testing urine iodine is a good way to determine if a specific group of humans has sufficient iodine. However, this test is not considered valid for individuals due to the variability of the results. In my practice, I take a dietary history. If the person consumes no seafood or saltwater fish (or less frequently than twice per week), no iodized salt (1/2 teaspoon each day) and no seaweed or dairy, I consider that person iodine deficient. I will find a way to give him/her iodine, ideally through food but if that is not acceptable or possible, through a good supplement (one that contains 150 mcg of potassium iodide per serving).
A word of caution: too much iodine can be as harmful as too little. If you are getting iodine through a supplement, make sure to carefully read the label. While the iodine amount in most vitamins is likely appropriate (75-290 micrograms), many iodine supplements contain thousands of micrograms (i.e., milligrams). This can make your thyroid sluggish or overactive.
In my next post, I will discuss additional nutrients that are necessary for optimal thyroid function.
Caldwell, K.L., Makhmudov, A., Ely, E., Jones, R.L. & Wang, R.Y. "Iodine status of the U.S. population, National Health and Nutrition Examination Survey, 2005-2006 and 2007-2008." Thyroid 21(4):419-27 Apr, 2011. www.ncbi.nlm.nih.gov/pubmed/21323596
"Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc." The National Academies of Science, Engineering and Medicine Consensus Study Report. 2001. www.nap.edu/catalog/10026.html
Leung, A.M., Lamar, A., He, X., Braverman, L.E. & Pearce E.N. "Iodine status and thyroid function of Boston-area vegetarians and vegans." J. Clin. Endocrinol. Metab. 96(8): E1303-7 Aug, 2011. www.ncbi.nlm.nih.gov/pubmed/21613354
Iodine Fact Sheet for Consumers: ods.od.nih.gov/factsheets/Iodine-Consumer/
Leung, A.M et al. "Potential risks of excess iodine ingestion and exposure: statement by the American thyroid association public health committee." Thyroid 25(2):145-6 Feb. 2015. www.ncbi.nlm.nih.gov/pubmed/25275241
Maria "Adi" Benito-Herrero, MD
Adi is an adult endocrinologist with training in Integrative Medicine from the University of Arizona. She also has certifications in herbal medicine from the David Winston Center for Herbal Studies and in meditation from Khalsa Healing Arts. In her private practice, she specializes in thyroid disorders, prediabetes and PCOS (polycystic ovary syndrome). Adi is Fellowship Faculty at the University of Arizona Center for Integrative Medicine. As a member of the Fellowship Faculty, she has authored the Center's Integrative Endocrine module. She is also the author of the thyroid chapter in the 2nd edition of Integrative Women's Health (Weil's Integrative Medicine Library) and has been an invited guest reviewer for www.DrWeil.com. Adi serves on the board of trustees of "The Suppers Programs," a non-profit organization based in Princeton, NJ. Suppers' mission is to help people lead healthier lives by eating deliciously prepared whole foods in a supportive setting, while respecting biological individuality.
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