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Why
Your Diet May Not Be As Rich In Iodine As You Assume
Author: ©Steve P Smith
The trace mineral iodine is well known for its crucial role in
enabling the body's manufacture of vital thyroid hormones, but
it is also important for the health of the immune system and for
optimal brain function. It is widely believed by many authorities
that iodine deficiency should never be seen in the affluent West,
although this problem affects millions throughout the developed
world.
Some nutritionists argue, however, that this conventional view
is too optimistic, because the content of all minerals in foods
is heavily dependent on the mineral content of the soil from which
those foods are derived. The assumption must therefore be that
the continuing de-mineralisation of farm soils has led to a reduction
in the amount of dietary iodine commonly consumed.
Fish and other seafood, however, remain a relatively rich source
because these ocean creatures concentrate the sea's iodine in
their flesh. Though not commonly eaten in the West, seaweed, or
kelp, is also an excellent source of iodine for this reason, and
is readily available in the form of a dietary supplements. Dairy
products and certain meats may also be a good source, particularly
where iodine is routinely added to farm animal feed. But in countries,
including most of Western Europe, where animals are grazing fields
growing on iodine depleted soils, levels are likely to be much
lower.
So even in the West, those not including fish or seafood in their
diets, and not using iodised or sea salt, may be at real risk
of deficiency. In an effort to compensate for low levels of dietary
iodine, the mineral has been routinely added to ordinary table
salt in the US for many years. But the practice is not as common
in the UK and other European countries, where specially iodised
or natural "sea-salt" has been marketed more as a luxury
alternative. The problem of insufficient dietary iodine has been
compounded on both sides of the Atlantic, however, by increasing
concern about the possible adverse health consequences, particularly
high blood pressure, of excessive salt intake. Many nutritionists,
however, regard these fears as exaggerated, and believe that any
such potential problems are far less serious than the consequences
of an insufficiency of iodine, and may be easily resolved by the
use of the low sodium salt alternatives available.
Iodine, however, cannot in any case be regarded as a luxury. Its
essential function lies in the production of the vital thyroid
hormones; thyroxine, sometimes known as T4, and tri-iodothyronine,
or T3. And as is well known, these hormones are crucially important
in ensuring a healthy metabolic rate and the release of energy
from food; so an underactive thyroid gland is commonly the villain
in cases of excessive weight gain, particularly where this of
sudden onset, and in cases of difficulty in losing weight even
when following a sensible reducing programme. A healthy thyroid
gland is also crucial for the optimal functioning of the immune
system.
But perhaps even more importantly, iodine deficiency is also known
as a major cause of avoidable brain damage; a problem which the
World Health Organisation has estimated to affect an astonishing
50 million people worldwide. Sadly, many of these cases occur
in children whose mothers were iodine deficient in pregnancy,
resulting in a condition of severely retarded brain development
known as congenital hypothyroidism, or "cretinism".
Even where such catastrophic consequences are avoided, iodine
deficiency in childhood may also have serious effects on the developing
brain, leading to low energy and motivation for learning, and
measurable impairment of IQ scores.
Since 2001 the Food and Nutrition Board of the US Institute of
Medicine (FNB) has prescribed a Recommended Dietary Allowance
for iodine of 150 mcg for all individuals over 14, rising to 220
mcg for pregnant women and 290 mcg for those breastfeeding. Somewhat
confusingly, however, an excessive consumption of iodine is also
associated with a malfunctioning or enlargement of the thyroid
gland, as well as mouth ulcers, headaches and gastric upsets,
and the FNB therefore advises an upper safe limit for daily iodine
consumption of 1,100 mcg for adults. Most people eating a conventional
Western diet are unlikely to exceed this level.
With the possible exception of pregnant and breastfeeding women,
people in the West who use liberal quantities of iodised salt
as a regular seasoning are unlikely to need further supplements.
But many commercial multi-mineral preparations contain iodine
in reasonable quantities, usually in the form of potassium iodide,
and whilst not perhaps strictly necessary, such supplementary
doses will do no harm and may be regarded as a useful insurance
policy given that, like all minerals needed by the body, iodine
functions best in the presence of adequate supplies of all the
others. And it should be particularly noted in this context that
the effects of any deficiency of iodine may be intensified by
any deficiency of selenium, iron or vitamin A.
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