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The thyroid is an organ located in the front of the neck that’s involved in several major bodily functions. Breathing, heart rate, body temperature and more are affected by how well the thyroid uses iodine from the food we eat to make thyroid hormones. Just like any complex machine, the body depends on moving parts that have to work precisely. For the thyroid to work properly, it needs just the correct amount of iodine.
Unfortunately, it’s relatively easy to throw the thyroid out of this delicate balance. Over-the-counter thyroid supplements may seem like a good idea to someone who believes they may have a thyroid condition. But thyroid supplements actually can cause problems with the thyroid. In general, I don’t recommend that people take these supplements.
LISTEN: Dr. Burman discusses thyroid supplements further on the Medical Intel podcast.
Keep an eye on iodine
Most people need about 150 micrograms of iodine per day (minimum daily requirement). That’s enough for the thyroid to make hormones to regulate the body’s metabolic processes. Iodine naturally is in many of the foods we eat, and it’s added to others. The following are just some of the many foods that contain iodine:
- Breads and cereals
- Dairy products, such as milk, yogurt and cheese
- Egg yolks
- Fish, shrimp and other seafood
- Fruits and vegetables
- Iodized salt
Pregnant women require a higher daily intake of iodine about 220 micrograms daily. Most of us get enough iodine from the food we eat. But some over-the-counter thyroid supplements can contain hundreds or thousands of micrograms of iodine per dose. This can put a person well over the National Institutes of Health Office of Dietary Supplements’ recommended maximum threshold of 1,100 micrograms of iodine per day for adults.
One source of iodine people often don’t know about is kelp, also known as seaweed. Kelp can contain massive amounts of iodine. One gram of kelp can contain as much as 8,165 micrograms of iodine, which is more than seven times the maximum daily amount for an adult. Kelp often is used in various preparations of seafood, especially sushi. It’s also a major source of iodine in various over-the-counter supplements.
1 gram of #seaweed can contain more than 7 times an adult’s maximum daily amount of #iodine. bddy.me/2AU1OVD via @MedStarWHC
In some patients with underlying thyroid gland autoimmunity issues (such as Hashimoto’s thyroiditis), getting too much iodine from either food or supplements can be dangerous. Because the body is getting too much iodine, the thyroid can start decreasing the amount of thyroid hormone it produces—ironically, the exact opposite effect of what someone taking thyroid supplements is hoping for. This can lead to the development of hypothyroidism, which is a deficiency of thyroid hormones in the body. Hypothyroidism can have symptoms that include:
- Anxiety, depression and forgetfulness
- Decreased sex drive
- Sensitivity to cold
- Weight gain
In other patients, or in the patients with a thyroid autoimmune issue, excess iodine intake may cause thyroid gland overproduction of thyroid hormones, or hyperthyroidism.
Watch out for nonprescription thyroid hormones
Normally, the thyroid creates the hormones triiodothyronine (T3) and thyroxine (T4) from the iodine we get in food. Some over-the-counter thyroid supplements go a step beyond by including iodine, as well as these hormones in their products.
Some people are getting more hormones than they’ve bargained for when they take over-the-counter thyroid supplements. Dr. Victor Bernet, who works at the Mayo Clinic in Jacksonville, Florida, was part of a team that studied the hormone levels of 10 thyroid supplements. The team’s findings, which were presented in 2011 to the American Thyroid Association, were shocking:
- Nine of the supplements had some level of thyroid hormone
- Five had an amount of T3 equal to or greater than 50 percent of the body’s total daily production
- Four contained T4, with some containing up to twice the body’s total required daily amount of T4
- Only one had no thyroid hormones
The hormone amounts present in these supplements can be higher than the amounts we prescribe to patients to treat hypothyroidism. Taking these high dosages of thyroid hormones actually can lead to hyperthyroidism, which is an excess of the hormones in the body. Symptoms of hyperthyroidism can include:
- Anxiety and irritability
- Fatigue and insomnia
- Feeling hot or sweating more frequently
- Irregular heartbeat, also known as arrhythmia
- More frequent bowel movements
How to reduce the risk of thyroid problems
I strongly suggest that people who have a diagnosed thyroid condition do not take over-the-counter thyroid supplements. You may be inappropriately increasing the amount of thyroid hormones in your body if you take these along with your prescribed medications.
I also recommend that people who haven’t been diagnosed with a thyroid condition avoid thyroid supplements. Self-medicating can lead to the development of the conditions you’re trying to avoid.
Be mindful of the iodine you’re getting as part of your daily diet. The National Institutes of Health Office of Dietary Supplements’ Selected Food Sources of Iodine table lists several common foods and their approximate iodine levels.
Finally, talk with your doctor about all the medications and supplements you take. Many daily multivitamins contain the daily recommended amount of iodine or more, so it’s easy to accidentally get too much, especially when combined with iodine-rich foods.
Not too high and not too low—like the story of Goldilocks, we want to keep your thyroid hormone levels just right.