Iodized salt imageYour body needs iodine, a mineral, to work properly. The thyroid gland, for example, uses iodine to make the thyroid hormone thyroxin. Most iodine is in the form of iodide. These terms are often used interchangeably.

Functions

Iodide helps to:

  • Regulate metabolic rate
  • Regulate growth and development
  • Promotes bone and protein synthesis

Recommended Intake

Age group Recommended Dietary Allowance [RDA]
(micrograms/day)
Upper Limits [UL]
(micrograms/day)
0-6 months110Not determinable
7-12 months130Not determinable
1-3 years90200
4-8 years90300
9-13 years120600
14-18 years150900
19-30 years1501,100
31-50 years1501,100
50-70 years1501,100
over 70 years1501,100
Pregnancy (18 or younger)220900
Pregnancy (19-50 years)2201,100
Lactation (18 or younger)290900
Lactation (19-50 years)2901,100

Too Little Iodide

If you do not have enough iodide, your body cannot make enough thyroxin. This slows down the rate at which the body burns energy, so weight gain can become a problem. This lack of iodide can cause a goiter , or enlarged thyroid gland. This happens when the thyroid gland grows to try and take up more iodide from the bloodstream. A chronic iodide deficiency can result in destruction of the thyroid gland.

Because we have iodized salt in the US, goiter is rarely seen. If eaten in large quantities, some foods, like raw turnips and rutabagas, have chemicals that can cause goiters and inhibit thyroid gland functions. These chemicals, called goitrogens, are destroyed when the foods are cooked, so problems are uncommon.

Too Much Iodide

The thyroid can also become enlarged if you have too much iodide in your diet, though this is rare in the US. This “toxic goiter” is caused by elevated concentrations of thyroid stimulating hormone (TSH). This is often seen in people who eat a lot of seaweed, which can add a significant amount of iodide to the diet. Iodide levels up to 1 milligram (more than six times the RDA) appear to be safe.

Major Food Sources

Iodide is found naturally in food grown in or near coastal seas. Seafood is naturally high in iodide, as are plants grown near the sea. Molasses and iodized salt are also good sources. Most people get plenty of iodide from the iodized salt in their diets, since only ½ teaspoon of iodized salt provides enough iodide to reach an adult's RDA for the day. The sea salt found in health food stores is generally not a good source because iodide is lost during processing.

FoodServing Size Iodide content
(micrograms)
Table salt, iodized¼ teaspoon100
Cod, cooked3 ounces87
Potato, cooked1 medium7
Spinach, cooked½ cup5
Almonds1 ounce4

Health Implications

When the thyroid gland releases fewer hormones than the body needs, the result is hypothyroidism. Some of the symptoms include:

When more hormones are released than necessary, the result is hyperthyroidism . Some symptoms include:

  • Heat intolerance
  • Tremors
  • Enlarged thyroid gland (goiter)
  • Heart palpitations
  • Increased sweating
  • Nervousness, irritability
  • Redness, swelling, and protrusion of the eyes
  • Shortness of breath
  • Increased number of bowel movements
  • Irregular or no menstrual period

A low iodide intake can especially impact children, causing a condition called cretinism . If not treated, the condition can lead to intellectual disability and abnormal growth. Iodine supplements can help reverse some of the affects. People who have a low iodide intake may be at risk of getting thyroid cancer, although it is not known exactly what causes the disease.

Tips for Increasing Your Iodide Intake

In general, there is little need to increase your iodide intake. Most people in the US get plenty from their diets, much of this coming from iodized salt. But if you use sea salt (or another type of salt) that does not have iodide, you can get the mineral from seafood or other sources. This is also true if you are on a low-sodium diet. Talk to your doctor if you are concerned about how much iodide you are getting.