Nutrition & supplements
Iodine & thyroid supplements
Should you take iodine for your thyroid?
The thyroid needs iodine to make its hormones, but too much iodine can cause the same thyroid problems as too little. Here is where iodine comes from, who may fall short, and why kelp and iodine supplements need caution.
In 30 seconds
The short answer
Your body needs iodine to make thyroid hormones, which control metabolism and support a baby's development.1 Most people in the U.S. get enough,12 mainly from iodized salt, seafood, dairy and eggs.23 Pregnant women and people who eat no dairy, seafood or eggs may fall short.56 But too much iodine can cause goiter and thyroid inflammation,9 so iodine pills and kelp need caution.
Why the thyroid needs iodine
Why the thyroid needs iodine
A simplified illustration based on NIH ODS and MedlinePlus.
Who may fall short, and who should be careful
| Who | Why |
|---|---|
| Pregnant women | Need about 50% more iodine.5 |
| Vegans, or little dairy, seafood or eggs | These are the best food sources.6 |
| People on antithyroid medicine | High-dose iodine can push thyroid hormone too low.10 |
| Anyone taking kelp or a multivitamin | Both can contain iodine; add it up.11 |
Severe deficiency in pregnancy can permanently harm the baby's development.7
Too much iodine
- Too much iodine can cause goiter, and high intakes can cause thyroid inflammation and thyroid cancer.9
- Very high intake can reduce thyroid function.18
- Kelp and many multivitamins contain iodine.11
- Potassium iodide only blocks radioactive iodine in a radiation emergency; it is not a general protection.17
From the Dr. Majid Ali archive
A historical perspective
“I have seen three cases of iodine toxicity created by blind, heavy, and prolonged iodine therapy.”— Dr. Majid Ali, 2015-10-16Dr. Ali wrote that iodine is the essential nutrient for the thyroid, and warned readers not to take iodine for more than a few weeks without testing, describing patients who developed thyroid disease from iodine overload.
That warning is consistent with current sources: too much iodine can cause goiter, thyroid inflammation and even reduced thyroid function.918
Where ProperHealth stops. Dr. Ali also wrote that iodine helps heal a wide range of inflammatory, infectious, immune and other disorders, and that many thyroid patients need iodine supplements. The sources used here do not support those claims; iodine deficiency is uncommon in the U.S.,12 and iodine with thyroid medicines can be harmful.10
Medicines, supplements and safety
A pharmacist can check your supplements for hidden iodine and review them against thyroid medicines. A pharmacist does not diagnose thyroid disease or change thyroid medicine doses.
Compared
Conventional and integrative care, compared
How thyroid disease is found and treated, where iodine supplements interfere, who actually runs short, and why "more iodine" is not a thyroid remedy.
What conventional treatment does
- An underactive thyroid develops slowly, and symptoms may go unnoticed for months or years;15 nearly 5 in 100 Americans 12 and older have one, more often women,13 and about 1 in 100 have an overactive thyroid.14 Untreated overactive thyroid can cause an irregular heartbeat leading to clots, stroke and heart failure.16 Potassium iodide only blocks radioactive iodine from the thyroid in a radiation emergency; it is not a general protection.17
Limits and adverse effects
- High-dose iodine with antithyroid medicines such as methimazole can make the body produce too little thyroid hormone.10 Very high iodine intake can reduce thyroid function,18 and too much iodine can cause goiter, and high intakes thyroid inflammation and thyroid cancer.9
- If you are pregnant and taking a thyroid medicine, contact your doctor right away about the dose.28
What contributes to the condition
- The body needs iodine to make thyroid hormones, which control metabolism and are needed for bone and brain development in pregnancy and infancy.1 Iodine deficiency is the most common cause of goiter,8 but it is uncommon in the United States.12 People on a vegan diet, or who eat little dairy, seafood or eggs, may not get enough;6 pregnant women need about 50% more iodine,5 and severe deficiency in pregnancy can permanently harm the baby's growth and development.7
Integrative and naturopathic approaches, by evidence
Evidence levels: EstablishedEmergingHypothesisNot supported
- Established
Seafood, dairy products and eggs are good sources of iodine;2 iodized salt is the main food source — a quarter teaspoon contains 78 micrograms.3 Processed foods almost never use iodized salt, and sea, kosher and Himalayan salts are not usually iodized.4
- Hypothesis
Many multivitamins contain iodine, and kelp supplements contain it too;11 the FDA does not approve supplements, including kelp and iodine products, before they are sold.19 Claims that high-dose iodine protects or "detoxifies" the thyroid in people who are not deficient are not supported by the sources used here.
- Not supported
Routine high-dose iodine or kelp for a thyroid that tests normal: too much iodine causes the very problems — goiter, inflammation — that people take it to prevent.9
New palpitations, weight loss or shakiness after starting iodine or kelp — stop it and see a provider.25
When to get help now
Each warning sign cites the official guidance behind it. The wording still needs pharmacist sign-off.
- A racing or irregular heartbeat, chest pain or fainting — call 911.2021
- A neck swelling that makes it hard to breathe or swallow — contact your provider. If breathing suddenly becomes hard, call 911.2223
- Severe tiredness, confusion or feeling very cold with a known underactive thyroid — seek care promptly.24
- New palpitations, weight loss or shakiness after starting iodine or kelp — stop and see a provider.252627
- Pregnant and taking a thyroid medicine — contact your doctor right away about the dose.28