Nutrients – Iodine

Iodine

Overview

Iodine is something I have been aware of since childhood. My mother always made sure she used iodized salt, both for cooking and for table use. This is something that I have been happy about, as both my first wife and now my second wife have been conscious about having iodized salt for use. Iodine is crucial in production of the thyroid hormone. Those of us living away from the coastal areas need to use iodized salt because there are few other ways to obtain iodine unless you are a heavy consumer of seafood from the oceans.

Iodine is a trace mineral that the body needs to make thyroid hormones, which are essential for normal growth and development. In your body, about 70 - 80% of iodine is found in the thyroid gland in the neck. The rest is distributed throughout the body, particularly in the ovaries, muscles, and blood. If your body doesn't have enough iodine, you can develop hypothyroidism (low thyroid hormone levels).

Tests for iodine deficiency

A 24-hour urine iodine collection is a useful medical test, as approximately 90% of ingested iodine is excreted in the urine. If a 24-hour urine collection is not practical, a random urine iodine-to-creatinine ratio can alternatively be used. According to the World Health Organization (WHO), in 2007, nearly 2 billion individuals had insufficient iodine intake, a third being of school age. Thus iodine deficiency, as the single greatest preventable cause of mental retardation, is an important public-health problem. In the USA, it is important the women bearing a child be tested and the newborn be tested as soon as can reasonably done.

Recommended Daily Allowance

The Food and Nutrition Board at the Institute of Medicine recommends the following dietary intake for iodine:

Infants

0 - 6 months: 110 micrograms per day (mcg/day)

7 - 12 months: 130 mcg/day

Children

1 - 3 years: 90 mcg/day

4 - 8 years: 90 mcg/day

9 - 13 years: 120 mcg/day

Adolescents and Adults

Males age 14 and older: 150 mcg/day

Females age 14 and older: 150 mcg/day

Specific recommendations depend on age, gender, and other factors (such as pregnancy). Women who are pregnant or producing breast milk (lactating) need higher amounts. Ask your doctor for the amount that is best for you.

Function

Iodine is needed for the normal metabolism of cells. Metabolism is the process of converting food into energy. Humans need iodine for normal thyroid function, and for the production of thyroid hormones. Iodine is a trace mineral and an essential nutrient found naturally in the body.

Food Sources

Iodized salt -- table salt with iodine added -- is the main food source of iodine. Seafood is naturally rich in iodine. Cod, sea bass, and haddock are good sources. Kelp is the most common vegetable seafood that is a rich source of iodine. Dairy products also contain iodine. Other good sources are plants grown in iodine-rich soil.

Precautions

Lack of enough iodine (deficiency) may occur in places that have iodine-poor soil. Many months of iodine deficiency in a person's diet may cause goiter or hypothyroidism. Without enough iodine, the thyroid cells and the thyroid gland become enlarged. No area maps for locations rich in iodine are currently available; however, seacoast areas are generally the highest in iodine.

Deficiency happens more often in women than in men, and is more common in pregnant women and older children. Getting enough iodine in the diet may prevent a form of physical and mental retardation called cretinism. Cretinism is very rare in the U.S. because iodine deficiency is generally not a problem.

Iodine poisoning is rare in the U.S. Very high intake of iodine can reduce the function of the thyroid gland.

Possible Interactions

If you are currently being treated with any of the following medications, you should not take iodine until you have first talked to your health care provider:

Antithyroid Drugs -- Use of antithyroid drugs, including propylthiouracil (PTU), and iodide may increase the hypothyroid effect of iodides.

Lithium -- Use of potassium iodide and lithium (Lithobid) may cause hypothyroidism.

Warfarin -- Use of potassium iodide (for hyperthyroidism) and warfarin (Coumadin, a blood thinning drug) may make warfarin less effective.

High blood pressure medication (ACE inhibitors and ARB's (Angiotensin Receptor Blockers)) -- Many iodine supplements contain potassium. When used with ACE inhibitors and ARB's, iodine may result in an increased level of potassium in the body, which may be dangerous.

Potassium sparing diuretics -- Since many iodine supplements contain potassium, concurrent use may result in dangerously high levels of potassium.

Amiodorone -- Concurrent use with iodine supplements may result in dangerously high levels of iodine.

Most people get plenty of iodine, and because of the complex way iodine can affect the thyroid, you should not take iodine supplements unless your doctor tells you to.