A Primal Primer: Iodine

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Yesterday I
mentioned that sea
vegetables are a great source of iodine
. “But what is iodine?”
many emailers asked. Well, dear friends, iodine is elemental. Let’s
take a trip through the land of iodine to learn what it is, what
it does for the human body and whether you should make an effort
to get more iodine in your diet.

What is
Iodine?

Iodine is a
highly water-soluble trace element that’s rare in the earth’s
crust, but fairly prevalent in its seas. Our bodies require it,
for several reasons. Our thyroid glands use it to make thyroid hormones
(T3 molecular weight is 59% iodine; T4 molecular weight, 65%), and
a severe
deficiency
can manifest in the development of goiter,
which is the thyroid gland swelling up in an attempt to keep up
the pace of iodine uptake from the blood and thyroid hormone production.
Lovely stuff, eh? Other common symptoms of iodine deficiency include
hypothyroidism and hyperthyroidism. It can also increase the incidence
of early mental retardation (iodine deficiency-related retardation
is the most preventable kind, in fact), and even stunted infant
brain development, provided the kid even makes it out alive: iodine
deficient pregnant
women
are at a higher risk for miscarriages and stillbirths.

Today, most
table salt has been iodized, and most processed food is in turn
made with plenty of iodized salt. As Richard
pointed out
a few months back, an unintended benefit of the
SAD may be the adequate intake of iodine! Ironically, hyper conscious
eaters who eschew all processed foods and sprinkle shavings of the
purest Himalayan salt blocks (reconstituted, perhaps, from the sweaty
pits of organic Sherpas) on their meals may be missing out on iodine.
Sea salt does contain trace amounts of iodine, being from the sea,
but what’s there degrades pretty rapidly. Subsisting on sea
salt alone is almost certainly inadequate for iodine intake. If
you avoid processed
food
(as you should), be sure to eat sea
vegetation
from time to time.

Iodine Dosage

Iodine dosage
is a tricky one to get a handle on. While the RDA of 150 micrograms
is sufficient to prevent goiters (kinda like the RDA for vitamin
D
is enough to prevent rickets), it probably isn’t optimal,
and humans can definitely handle larger intakes. After all, coastal-dwelling
sorts, like the Japanese, have regularly been consuming iodine-rich
sea vegetables for ages without wide-scale thyroid problems –
some even suggest this level of intake is preventive
against thyroid disorders and breast cancer
. Most accounts put
them at 5–12mg of iodine daily. The Japanese also consume a
fair amount of soy, which has been shown to be antagonistic to iodine
uptake, so perhaps they’ve found a balance between the two.
At the same time, iodine supplementation can be overdone, leading
to hyperthyroidism.

I lean toward
the RDA being short sighted and rather inadequate, to be honest.
The tolerable daily upper limit of 1 mg seems better. As they tend
to do, the experts cast iodine in a single, solitary role –
as the prime regulator of thyroid health and function – and
ignore any possibility that it’s important in other realms,
too. That’s madness, just like it’s madness to presume
vitamin
D
is only about protecting rickets, even as evidence of its
cardio-, immuno-, and carcino-protective effects mount. It’s
often stated that the thyroid only needs around 100 micrograms of
iodine per day to manufacture sufficient amounts of thyroid hormone
and this is used as evidence of the RDA’s accuracy. But only
30% of the body’s total iodine content is concentrated in the
thyroid. The rest of it is found in the mammary glands, eye, gastric
mucosa, cervix, thymus gland, and salivary glands. If the body is
doing something with any sort of consistency, if there’s a
pattern to its processes, it’s probably playing an important
– even if not entirely understood – role.

Let’s
take a closer look at how iodine functions in the human body.

Fetal Development

The fetal thyroid
gland begins to function at the 11 week mark of gestation, and at
the 18th week, T4 is being produced by the fetus in order to develop
its nervous system. The child’s neurological development also
depends on proper functioning of the fetal thyroid glands. Sufficient
iodine intake (by the mother, of course) is required for sufficient
thyroid action in the fetus, just as it’s required in adult
thyroids.

Breastfeeding

After birth,
the child still depends on the mother for his or her iodine. Those
little brains are experiencing their most rapid period of growth
and development, and they need plenty of iodine to avoid impaired
cognitive development. Nursing
increases the dietary requirement for iodine.

Read
the rest of the article

July
13, 2010

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