Iodine

Description

Iodine is an essential Elements involved in normal growth and development, and originates in the soil and sea.

Functions

Iodine forms part of the hormones thyroxine and triiodothyronine that are necessary for the maintenance of metabolic rate, cellular metabolism and integrity of the connective tissue.

The body content of iodine is between 20 and 50mg, mostly concentrated in the thyroid gland situated in the base of the neck. Any iodine in the diet is quickly absorbed from the intestinal tract, mostly in the form of iodide, which is stored by the thyroid until needed. In the thyroid iodide is oxidised into iodine, combined with the amino acid tyrosine and eventually converted into thyroxine which is stored until required. This process is controlled by a hormone produced in the pituitary gland.

Deficiency

The classic deficiency disease of iodine is "goitre" which is marked by a swelling of the thyroid gland in the neck. This swelling occurs as an attempt by the thyroid gland to produce more thyroxine in the face of an iodine insufficiency.

In severe cases of deficiency, cretinism results, with poor brain development and mental retardation.

With the consumption of foods grown in soils all around the world, iodine deficiency has become a rare occurrence in Britain. Certain countries also add iodine to table salt.

Requirements

Upper safe level for daily supplementation = 500µg

Recommended Daily Allowance = 150µg

Supplemental Uses

Iodine in the form of Kelp may be taken to stimulate a slightly underactive thyroid gland that does not warrant medical treatment (1).

More usually, iodine is included in small amounts in multi vitamin and mineral formulations that are suitable for use by all normal healthy people.

Safety

Very high iodine intakes can cause an over-active thyroid gland, but few cases of toxicity have been reported in people consuming less than 5000mg iodine daily. Transient mild effects may however be noted in previously deficient individuals taking only 150-200mg per day. Normal subjects with an iodine intake of 1000-2000mg iodine daily show an increase in the iodine content of their thyroid gland, but no further changes.

Interactions and Contra-Indications

Thyroid Medication
High levels of iodine should not be taken by people on medication for thyroid problems unless under a doctor’s advice.

Pregnancy
High intakes of iodine should not be taken by pregnant women as the foetus is more sensitive to hyperthyroidism than the mother.

Food Sources

The iodine contents of plant foods vary depending on the soil in which they are grown.

Food (mg/100g)
Kelp up to 5000
Haddock 659
Whiting 65-361
Herring 21-27
Meats 10
Vegetables/grains 10