References used for all of the nutrient pages can be found at the bottom of the Nutrition Facts page. Click here.

​How Much Iodine Do I Need?

  • RDA for Adults: 150 mcg/d

  • Upper Safe Limit for Adults: 1100 mcd/d

Why Do I Need Iodine?

  • Iodine is an essential component of 2 thyroid hormones that regulate growth, development and metabolism

Plant-Based Sources 

  • Iodized salt and sea vegetables like dulse, nori (aka laver) and alaria are the most reliable plant-based sources

  • In general, a teaspoon of iodized salt contains 68 mcg

  • Seaweed can vary greatly (between 16 and 2984 mcg per serving) and Dr. Greger advises that people stick to the lower iodine content seaweeds such as dulse, nori and alaria to avoid toxicity

  • The sea vegetables hijiki (aka hiziki) and kelp (aka kombu) should be avoided due to excessive arsenic content and excessive iodine content respectively

  • The iodine content of other plant foods can vary based on the soil in which they were grown, fertilizer use and irrigation practices

  • Due to the variability in iodine content, the USDA food composition database tables do not provide the iodine content of foods

Deficiency Symptoms

  • Enlargement of the thyroid gland known as simple goiter

  • Weight gain

  • Mental and physical retardation of an infant​​​

Toxicity Symptoms

  • ​High levels of iodine can cause the same symptoms as iodine deficiency, including goiter

  • High iodine intakes can also cause thyroid gland inflammation and thyroid cancer

  • Very large doses of iodine (several grams, for example) can cause burning of the mouth, throat and stomach; fever; stomach pain; nausea; vomiting; diarrhea; weak pulse and coma

How to Assess Status

  • Your doctor can check your iodine status several ways including a urine iodine measurement and blood measurement of thyroid stimulating hormone


  • Adults who follow a strict plant-based diet who do not use iodized salt or consume sea vegetables might consider taking a supplement containing up to 100% of the RDA

  • ​There are many healthy foods that are considered goitrogens

  • Goitrogens are foods that interfere with thyroid function in people with marginal iodine intake

  • Goitrogens include: soy, cabbage, kale, brussels sprouts, cauliflower, broccoli and kohlrabi

  • It is NOT recommended that you avoid these healthy foods but it is important that you get adequate iodine to prevent thyroid problems


The following videos by Dr. Michael Greger highlight some important issues regarding iodine:


Kristen Zaier, ​​Plant-Based RD