Iodine and the thyroid — worth a second glance
We’ve all heard of iodine, of course. But if we were asked to define iodine’s
role in human health, we might either think of it as merely an added ingredient
to table salt (though many people don’t know why exactly), or as the bright
orange tincture used by our parents to disinfect our childhood cuts and scrapes.
But iodine is the critical element for healthy thyroid hormone production,
and if it’s not available in the tiny amounts needed by the thyroid gland,
there can be wide-ranging physical consequences.
These days, I have a growing concern that many of us may not be getting enough of
this essential element. But although evidence of widespread iodine deficiency seems
clear to me, the idea is still controversial in conventional medical circles. In
a recent Newsweek article, an eminent medical school professor pronounced
iodine deficiency to be rare in women in the US. Many of the magazine’s readers
might not even give the subject a second thought. Yet compelling data were recently
reported by the Centers for Disease Control suggesting that some 2.2 million women
nationwide could have low iodine.
To learn more about the roles iodine, selenium, and other key nutrients play in
thyroid function, see our article on
eating for thyroid health.
As we learn more about how iodine functions in the body, research is revealing connections
between diet, environment, and the rise of thyroid, breast, and immune health problems
in women. Maybe you’ve had recent thyroid testing that came back borderline,
or you’ve been diagnosed with hypothyroidism (inadequate production
of thyroid hormones), and you’re already on thyroid medication. Perhaps you
have fibrocystic breast condition and avoid salt by choice or due to high blood
pressure. If so, it’s possible you could benefit from more insight into your
iodine status and available testing and treatment options.
Iodine deficiency — how common is it?
As a practitioner of functional medicine, I am more and more intrigued by iodine.
How widespread is iodine deficiency? Why is it downplayed, and even overlooked here
in the US? When iodine deficiency was first recognized as a public concern in the
1920’s, iodine was subsequently added first to flour, then to salt, and the
problem was considered solved.
In the US, it’s estimated that one in seven women suffers from iodine deficiency.
— Caldwell, K., et al. 2005.
— Hollowell, J., et al. 1998.
But many people don’t know that flour isn’t iodized anymore, and iodization
of salt is still voluntary in the US — only one-fifth of our salt is actually
iodized. In reading further, I’ve found that we’re trending back toward
iodine deficiency. Iodine intake has declined 50% in North America in the past 30–40
years, and this is consistent with what I’m seeing in my patients.
As recently as 2004, the New England Journal of Medicine defined our iodine
status here in the US as “marginal,” based on data acquired from the
for the Control of Iodine Deficiency Disorder and the World Health Organization
(WHO). More specifically, the WHO data suggest the greater risk in the US is not
iodine deficiency per se but iodine-induced hyperthyroidism (overproduction
of thyroid hormones) or iodine-induced hypothyroidism. Interestingly, both
these problems can occur when people who are already iodine-deficient are given
too much iodine, too quickly. I believe practitioners need to proceed more
cautiously when prescribing iodine supplements, slowly bringing levels up
rather than overloading right up front. (More on our treatment protocol for iodine
deficiency below.) But the WHO perspective seems to confirm that iodine deficiency
does exist here in the US.
8 dietary sources of iodine
The sea is where it’s at when it comes to iodine. Seafood and seaweeds (sea
“vegetables”) are excellent sources.
Best by far...
1. Sea vegetables, sea vegetables, sea vegetables!
2. Saltwater fish and other seafood
3. Iodized seasalt
Foods that contain some iodine...
5. Dairy products
Remember, even iodized salt is not as high in iodine as you may think. Also look
for iodine in your daily multivitamin-mineral complex — that’s why we
put it in our Personal Program
* Dasgupta, P., et al. 2008. (See
Iodine deficiency may often be overlooked because the symptoms overlap with those
of other illnesses, perhaps masking the problem. The 2004 National Health and Nutrition
Survey helped dispel the assumption that iodine deficiency in women is a myth: although
there was some leveling off of the drop in overall intake, more than a
third of women of childbearing age had insufficient iodine levels. From thyroid
issues to breast concerns to cognitive function, this could have serious implications
and long-term health as well as that of their children. In my clinic, I’ve
noted marginal levels in my patients and am seeing a distinct downward
trend of levels in new patients.
From intake to uptake — why are some of us so iodine-deficient?
One-third of the world’s population lives in iodine-deficient areas: very
little of the earth’s iodine is found in topsoils, and even where this mineral
is present, it may remain tightly bound up in soil particles. This is the main reason
why land vegetable crops are generally not good dietary sources. Women with symptoms
of hypothyroidism should have their iodine levels evaluated, especially if they
don’t eat many iodine-containing foods (See box at right for good dietary
sources of iodine.)
Factors impacting our iodine intake
- Iodine’s relative scarcity in most environments
- Changes in our diet and environment
* Kopp, P. 2008. (See
But even while we humans have lived for millennia in an iodine-poor environment,
the more pressing problem may be the novel burdens our modern surroundings are placing
on our systems. Together with our lack of understanding, factors that make it harder
than ever to acquire and retain enough iodine include toxic halide chemicals
in our environment filling the iodine void in our bodies; the “demonizing”
of salt; overfishing; and ocean pollution.
Iodophobia. Iodine is one of the essential nutrients that
you can get too much of. So both excess iodine and iodine deficiency can
impair thyroid function and lead to elevated thyroid-stimulating hormone
(TSH) levels. But it’s likely that if you are iodine-replete, you’re
less sensitive to excess iodine than people with chronically depleted levels.
In the US, the recommended daily allowance (RDA) for iodine for adults is 150 mcg/day
and 290 mcg/day for lactating women. More and more researchers are saying that increasing
the RDA would greatly benefit breast, thyroid, and nervous system health in women
and infants. Our current RDA is well below the US Food and Nutrition Board’s
“upper limit of safety” for iodine (UL = 1100 mcg), which is even lower
in Europe (UL = 600 mcg), where iodine deficiency is more common. In Japan, however,
where diets include lots of iodine, consumption is about 25 times more than the
median intake here, yet the Japanese do not have more thyroid iodine toxicosis.
Do we need mandatory universal salt iodization?
If all salt in the US were iodized, a five-fold increase in iodine intake could
take place without increasing our salt intake.
* Dasgupta, P., et al. 2008. (See
Individual sensitivity to iodine varies widely, but in the past 10–15 years, experts
have found that overall, we are “remarkably tolerant to high intakes of iodine.”
It appears that low or high iodine intake is something we get used to over
long periods of time — though we’ll always need a certain amount. People
living in some coastal regions of Japan regularly consume as much as 50,000–80,000
mcg of iodine daily!
If you’ve never been iodine-deficient, your thyroid will tend to stay normal
in function and size if you consume up to several milligrams of dietary iodine daily.
If you’ve been deficient, you may be hypersensitive to iodine. In my experience,
this is not a problem for most women, and even hypersensitive individuals can just
gradually adjust their levels upward.
Salt as the enemy. There is a common perception that salt
itself is dangerous. Because excessive sodium intake can increase the risk
of hypertension, as many as 7 out of 10 women avoid or rarely use it. What’s
more, the American Medical Association has recently suggested the USFDA remove salt
from the list of foods “Generally Recognized as Safe” (GRAS)!
Contrary to popular belief, four-fifths of the salt in American food is not iodized.
That would be fine if we only consumed fewer over-salted, processed, prepackaged,
and fast foods (which do not contain iodine), while increasing our intake of sea
foods, alkalizing mineral salts (such as potassium citrate, calcium carbonate, calcium
ascorbate), and quality iodized sea salt. Not only would we see fewer problems with
hypertension, we’d be healthier in every way — with most of us able
to excrete any extra sodium we might consume.
The problem with other halogens. Iodine deficiency may
also be related to other halogens — non-metals such as fluoride,
chloride, and bromide, which are replacing iodine in the body.
Most public water drinking supplies include the first two. Perchlorate
(which may derive from rocket propellant, Chilean nitrate fertilizers, or other
sources) is known to inhibit iodine transport in the body and thyroid function.
Some scientists believe the omnipresence of perchlorate is “putting future
generations in peril.”
Bromide is also widely present — in soil and crop fumigants as well many foods
and drugs. In the 1960’s, iodine was added as an anticaking agent to bakery
products, but because of misplaced fears of iodine toxicity (“iodophobia”
), it was replaced with bromine in the 1980’s. So we’re ingesting a
lot of these halides, which research suggests compete with iodide for absorption
and uptake in the body. This means they function as goitrogens (substances that
suppress thyroid function by interfering with iodine uptake/accumulation).
According to leading iodine expert Dr. David Brownstein, iodine will bind to fluoride,
chloride, and bromide, as well as to mercury, so these molecules can be removed
from the body. But that process depends heavily on having adequate iodine in the
body. If you are iodine-deficient, know that other toxic chemicals have taken its
place in your body so that when you then add it back in, you’re both detoxing
these chemicals and adjusting to the new iodine.
How’s your iodine? — iodine testing and treatment
It’s always best to solve the underlying causes of symptoms. If you have symptoms
of hypothyroidism, fibrocystic breasts, fatigue, or brain fog, you may want to rule
out iodine deficiency as a potential cause or contributor. Iodine functions as a
chelating agent, a powerful antioxidant, and as a player in the metabolism of many
other hormones, including adrenal and sex hormones — so it’s important
to be sure you have enough!
Simple self-test for iodine deficiency
To check whether you have enough iodine on board, you can try this safe self-test
at home. Simply dip a clean ball of cotton in inexpensive red-tinged USP tincture
of iodine from any drugstore. Paint a 2-inch circle of tincture of iodine on soft
skin tissue, such as the inner arm or thigh.
Now wait: if the yellow-orange stain takes more than 6 hours to disappear, you are
likely to be iodine-replete. If the stain is absorbed quickly (within 1–3 hours),
your body may need a higher iodine intake.
The next step is to ask your healthcare provider for the more accurate, 24-hour
iodine/iodide loading test.
* Skidmore, B. 2007. (See
Based on my clinical experience and what I’ve learned from my colleagues,
I consider the possibility of iodine deficiency in each new patient I see. Depending
on a woman’s symptoms and circumstances, I may also test her iodine levels
using a 24-hour iodine/iodide loading test. This test is controversial,
because preparation and collection guidelines must be followed carefully to obtain
accurate results. The individual being tested avoids iodine and other halogens before
undergoing the test then is “challenged” by taking an amount of iodine.
After that, the excretion amounts of iodine and certain other elements from the
halogen family are measured.
After evaluating the results of this test, I may institute a careful treatment protocol,
slowly introducing an iodine replacement drug called Iodoral, in dosages
determined by Dr. David Brownstein and others. What I see with this protocol is
that iodine levels do not just come up quickly, as the body replaces toxic halides
and mercury with iodine. When paced correctly, this regimen — which takes
time but has been extremely helpful for many of our patients — helps women
avoid the palpitations and anxiety that can occur if iodine levels rise too abruptly.
You can get a sense for whether you may be iodine-deficient using a self-test with
an iodine tincture (see box at right). Accurate, more useful results can be obtained
only through laboratory testing. With actual numbers, you and your healthcare practitioner
can work together to appropriately replete your iodine levels.
The practice of iodine testing and treatment is a relatively emergent science that
holds tremendous potential for improving women’s immune, breast, and thyroid
health, and consequently our longevity. As we raise our awareness and understand
more about how iodine works in the body, we can overcome any lingering “iodophobia”
and begin to fully appreciate the value of this essential mineral.
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on iodine and the thyroid
Last Modified Date: 05/27/2011
Principal Author: Marcelle Pick, OB/GYN NP