Glossary Detail

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name of the term: Iodine

Short introduction

  • Iodine is a trace-element with the symbol I.
  • The thyroid gland (in front of the neck) contains most of the iodine in the body.

Main natural sources

  • The iodine content of most foods depends on the iodine content of the soil.
  • Seafood is rich in iodine because marine animals can concentrate iodine from seawater. Seaweed is a concentrated source of iodine.
  • Main sources: milk and dairy products.
  • In many countries, iodine is added to table salt. Also bread may contain iodised salt.

Main function

  • Iodine in the thyroid gland is necessary for the formation of thyroid hormones: triiodothyronine (T3) and thyroxine (T4) and essential for normal thyroid function.
  • The thyroid gland traps iodine from the blood and incorporates it into thyroid hormones that are stored and released into the circulation when needed.
  • Thyroid hormones (and so indirectly iodine) are needed for many body processes including growth, regulating (energy) metabolism. Several other trace-elements are also required for proper thyroid hormone metabolism e.g. selenium.
  • Thyroid hormones are needed for brain development: they are important for myelination of the central nervous system, the formation of the myelin sheath around a nerve fiber – allowing rapid and efficient transmission of nerve impulses.

Deficiency disease

  • Iodine deficiency is rare in areas where iodised salt is used but common worldwide.
  • Iodine Deficiency Disorders (IDD) result from inadequate thyroid hormone production secondary to insufficient iodine and have an effect on growth and (brain) development.
  • When iodine intake is inadequate, the thyroid gland gets larger in an attempt to make more thyroid hormone. This overgrowth is called goitre and the most visible sign of iodine deficiency.
  • If the deficiency is long term, hypothyroidism develops: not enough thyroid hormone is produced. Symptoms include dry skin, hair loss, fatigue and slowed reflexes.
  • In the developing foetus, baby or young child, the effects of iodine deficiency are serious. They include stunted growth, diminished intelligence and retardation.
  • Severe iodine deficiency can cause cretinism (condition of severely stunted physical and mental growth) and adversely affect cognitive development in children.
  • Iodine deficiency is one of the world's greatest single causes of preventable brain damage and mental retardation, producing typical reductions in IQ of 10 to 15 IQ points.

Recommended daily intake

Latest Dietary Reference Intakes  (DRIs) 
Institute of Medicine (IOM)

Age categoryPer day

Pregnancy
Lactation

220 μg (RDA)
290 μg (RDA)
Infants 6 – 12 months130 μg (AI)
Children
 1 – 3 years
 4 – 8 years
90 μg (RDA)
90 μg (RDA)
Males
 9 – 13 years
14 – 18 years
19 – 30 years
31 – 50 years
50 – 70 years
> 70 years
120 μg (RDA)
150 μg (RDA)
150 μg (RDA)
150 μg (RDA)
150 μg (RDA)
150 μg (RDA)
Females
 9 – 13 years
14 – 18 years
19 – 30 years
31 – 50 years
50 – 70 years
> 70 years
120 μg (RDA)
150 μg (RDA)
150 μg (RDA)
150 μg (RDA)
150 μg (RDA)
150 μg (RDA)

 

AI = Adequate Intake.
RDA = Recommended Dietary Allowance.

Synonyms: Iodine

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