Am I Getting Enough Iodine?
by Reed Mangels, PhD, RD
A reader contacted us and asked, "Since many people are cutting down on their use of added salt (eliminating added salt in some cases), how can vegans be sure they are getting enough iodine in their diet?"
This is a reasonable concern since the iodine content of plant foods is often low, and their iodine content depends on factors such as the concentration of iodine in the soil where the plants were grown.1 Iodine is an essential mineral that is needed for the thyroid gland to work properly. Not getting adequate iodine can have negative effects on the thyroid gland. Iodine deficiency in infants and children can result in poor growth and development.
Prior to the 1920s, in the United States, an iodine-deficiency disease called endemic goiter was relatively common. The incidence of endemic goiter fell sharply after iodized salt was introduced in the United States. Salt iodization is not mandatory in the United States, but there are requirements for the amount of iodine that is added to iodized salt. Iodized salt provides about 76 micrograms of iodine in a quarter teaspoon. About half of the U.S. population uses iodized salt.2 If you avoid added salt, your diet may be low in iodine, much like the diet of Americans prior to 1924.
"Well," you may be thinking, "I eat some salty processed foods. I must get iodine from that." Actually, most processed foods, as well as products from fast food establishments, are not made with iodized salt. If a food manufacturer does use iodized salt, the iodized salt must be listed as an ingredient.3
Sea vegetables can be a source of iodine, although the amount is inconsistent. Sometimes, sea vegetables are very high in iodine and that can cause health issues. The bioavailability of iodine from sea vegetables is also quite variable.4
If you are vegan and don't use iodized salt regularly, I recommend that you use a supplement containing iodine. Many multivitamin/multimineral supplements contain iodine, and iodine is also available as a separate supplement. The Recommended Dietary Allowance (RDA) for iodine for adults is 150 micrograms per day. If you choose to use an iodine supplement, you should look for one providing approximately this amount.
References
1 Ershow AG, Skeaff SA, Merkel JM, Pehrsson PR. Development of databases on iodine in foods and dietary supplements. Nutrients. 2018;10(1):100.
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 Academies Press, 2001.
3 Pennington JA, Young B. Iron, zinc, copper, manganese, selenium, and iodine in foods from the United States Total Diet Study. J Food Compost Anal. 1990;3:166-184.
4 Dominguez-Gonzalez MR, Chiocchetti GM, Herbello-Hermelo P, et al. Evaluation of iodine bioavailability in seaweed using in vitro methods. J Agric Food Chem. 2017;65:8435-8442.
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