Iodine
DESCRIPTION:
Iodine is an essential element
involved in normal growth and development, and originates in the
soil and sea.
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.
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.
Upper safe level for daily
supplementation = 500µg
Recommended Daily Allowance = 150µg
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 multivitamin and mineral formulations that are
suitable for use by all normal healthy people.
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.
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
Related News Stories
Vegans are at risk of not getting
adequate amounts of iodine in their diet, which could result in
a deficiency.
Recommended doses of iodine and
damage this helps prevent against.
Deficiencies in certain nutrients
may have links to complications in pregnancy.
