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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
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