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Iodine

What does it do?

Iodine is an essential constituent of your thyroid hormones, which help regulate metabolism (the rate at which your body uses energy). Iodine is a key player in many biochemical reactions that affect heart rate, respiratory rate and a wide variety of other physiological activities.

What are the best food sources?

The iodine content in foods varies widely due to soil content, irrigation and fertilizer. It is usually low in areas that are eroded or are distant from oceans, the source of most of the world’s iodine. Seafood and seaweed are rich natural sources. Processed foods may contain higher levels due to the addition of iodized salt or other additives containing iodine (e.g., calcium iodate). In the United States, iodized salt is widely available. However, salt is not required to be iodized. One-fourth of a teaspoon of iodized table salt contains about 100 micrograms of iodine.

What happens if you don’t get enough?

Due to the widespread use of iodized salt, deficiency is rare in the United States. However, iodine deficiency affects millions of people worldwide and is identified as the most common cause of preventable brain damage in the world. Major international efforts are currently under way to reverse and prevent this problem. Iodine deficiency disease (IDD) results in a range of symptoms from mild to severe including goiter (an enlarged thyroid gland and usually the earliest sign), mental retardation, hypothyroidism (too little thyroid hormone), and varying degrees of growth and development abnormalities.

What happens if you get too much?

Individuals can tolerate a wide range of iodine intakes because the thyroid gland regulates the body’s level of this mineral. Acute intakes—those ingested over a short time period—can cause burning of the mouth, throat and stomach; fever; gastrointestinal illness, such as nausea, vomiting and diarrhea; a weak pulse; and coma. In iodine-sufficient populations, chronic intakes at levels above the tolerable upper intake level (UL) have the following adverse effects: goiter (an enlarged thyroid gland), hypothyroidism (too little thyroid hormone), hyperthyroidism (too much thyroid hormone) and thyroiditis (inflammation of the thyroid gland).

How much do you need?

The following table lists the recommended intake for healthy people based on current scientific information.

Life Stage Group Age Range Recommended Dietary Allowance/Adequate Intake Tolerable Upper Intake Level (UL)
Infants 0-6 mo. Not determinable for infants due to lack of data on adverse effects in this age group and concern about inability to handle excess amounts. Source should be from food only to prevent high levels of intake.
Infants 7-12 mo. Not determinable for infants due to lack of data on adverse effects in this age group and concern about inability to handle excess amounts. Source should be from food only to prevent high levels of intake.
Children 1-3 yr. 200 micrograms/day
Children 4-8 yr. 300 micrograms/day
Males 9-13 yr. 600 micrograms/day
Males 14-18 yr. 900 micrograms/day
Males 19-30 yr. 1100 micrograms/day
Males 31-50 yr. 1100 micrograms/day
Males 51-70 yr. 1100 micrograms/day
Males > 70 yr. 1100 micrograms/day
Females 9-13 yr. 600 micrograms/day
Females 14-18 yr. 900 micrograms/day
Females 19-30 yr. 1100 micrograms/day
Females 31-50 yr. 1100 micrograms/day
Females 51-70 yr. 1100 micrograms/day
Females > 70 yr. 1100 micrograms/day
Pregnancy < 18 yr. 900 micrograms/day
Pregnancy 19-30 yr. 1100 micrograms/day
Pregnancy 31-50 yr. 1100 micrograms/day
Lactation < 18 yr. 900 micrograms/day
Lactation 19-30 1100 micrograms/day
Lactation 31-50 yr. 1100 micrograms/day

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