Iodine is one of the most important nutrients you need
to keep your thyroid working well — and it has a major effect on your entire body.
That’s why when you have an iodine deficiency, you’ll feel sluggish overall. Plus
you’ll experience a wide range of symptoms throughout your body that are related
to a low thyroid function, such as fatigue, sensitivity to cold and unexplained
Most of us may only think of iodine as an added ingredient in table salt, and not
as a key mineral we need for our health. While iodine deficiency is certainly not
common, it does exist, especially for certain women. For example, women of childbearing
age (20-39) in the US had the lowest urine iodine levels of any other age group,
according to a 2012 CDC report. It’s important to consider what effect your iodine
level could be having on your thyroid, as well as understand that too much iodine
– especially all at once – can also cause problems.
Are you sure that you’re getting the right amount of iodine your thyroid needs to
do its job and for you to feel your best? Here’s a closer look at why iodine is
important for your thyroid, how to know if you’re getting enough (or too much) iodine
and what foods are good sources of iodine.
Why is iodine important for your thyroid?
Iodine is a critical element needed to make
the essential thyroid hormones that circulate in your body. These hormones
– known as T4 (thyroxine) and the more active T3 (triiodothyronine)
– ensure healthy signaling between your thyroid, brain and body to regulate your
energy, weight, cell metabolism and much more. Unfortunately, the feedback loops
between the thyroid and the brain can easily be disrupted when you aren’t getting
enough of specific nutrients like iodine, selenium, tyrosine and B vitamins.
Even though iodine is so important to so many of your body’s functions, your body
doesn’t make it. You need to make sure you’re getting adequate amounts of iodine
from your daily diet, along with supplements when needed, so that your thyroid has
the most basic building-blocks to make its key hormones.
Good sources of iodine in your diet
Your thyroid only needs tiny amounts of iodine on a daily basis, so looking at your
food choices is a good place to start for boosting your iodine intake. Some of the
top food options to add to your everyday diet include:
Top food choices for iodine include:
- Sea vegetables (such as kelp, dulse, hijiki, nori, arame, wakame and kombu)
- Seafood (such as clams, shrimp, haddock, oysters, salmon and sardines)
- Iodized sea salt
Secondary food sources for iodine include:
- Lima beans
- Sesame seeds
- Summer squash
- Swiss chard
- Dairy products
When it comes to the amount of iodine that you’re getting from food, it’s important
to remember that even iodized salt is not as high in iodine as you may think. Plus,
with many women now watching their salt intake, you may not be getting as much iodine
in your daily diet as you did in the past.
In addition to iodine,
selenium is another important mineral you need for good thyroid health.
Selenium helps the body to recycle iodine. If you have low levels of selenium along
with low levels of iodine, it is more likely to lead to a thyroid imbalance.
You can read more about the needed nutrients for your thyroid and the top foods
that contain them in our article
What to eat to support your thyroid reviewed by Dr. Mary James, ND.
How much iodine do you need?
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
The 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.
You can get too much iodine
You can also experience thyroid health issues from too much iodine. Iodine-induced
hyperthyroidism (overproduction of thyroid hormones) or iodine-induced hypothyroidism
can both occur when people who are already iodine-deficient are given too much iodine,
too quickly. Take care when starting with iodine supplements, slowly bringing levels
up rather than overloading right up front. You may want to consult with your healthcare
Should you get your iodine levels tested?
If you think you could be suffering from low thyroid, subclinical hypothyroidism
or even hypothyroidism (inadequate production of thyroid hormones) it makes sense
to have your iodine levels tested. This is especially important if you don’t eat
many iodine-containing foods or use iodized sea salt. As we learn more about how
iodine functions in the body, we’re seeing more and more connections between diet,
environment and the rise of thyroid health problems in women.
Here’s a simple test for iodine deficiency that you can safely do at home:
- Dip a clean ball of cotton in inexpensive red-tinged USP tincture of iodine from
- Paint a 2-inch circle of tincture of iodine on soft skin tissue, such as the inner
arm or thigh.
- Wait to see what happens: 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.
- Depending on your results, you may want to talk with your healthcare practitioner
for the more detailed 24-hour iodine/iodide loading test.
Reference: Skidmore, B. 2007
You may also want to consider additional testing if you think you have a thyroid
issue. Talk with your doctor about getting a full thyroid hormone panel, along with
testing for your iodine, selenium and vitamin D levels.
If you have low thyroid
symptoms, the more you know about thyroid nutrition, the better.