Finding the Right Balance of Iodine in Pregnancy

If you are planning to get pregnant, you know that your diet is critical for a healthy baby. Consuming the right balance of nutrients and avoiding harmful habits become even more important.

Iodine is one of the nutrients your body needs in different amounts during pregnancy. Too little of it can keep your baby from developing properly. Yet too much of it can cause thyroid problems for both of you.

If you already have thyroid disease, striking the right balance can be even trickier.

Should you take iodine supplements? What about a prenatal with iodine? Should you go out of your way to include iodine-rich foods or avoid them?

This blog will help you understand the importance of iodine in pregnancy and help you choose the best amount for you and your baby. Proven iodine-balancing plan in the Thyroid Reset Diet Book.

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Table of Contents

Why is Iodine Important in Pregnancy?
How Much Iodine Does a Pregnant Woman Need?
What Does That Mean in Terms of Daily Intake?
Taking Iodine Supplements During Pregnancy
Resources

Why is Iodine Important in Pregnancy?

Thyroid hormones need to be just right for proper development. Fetal brain development is especially sensitive to a gentle nudge from mom’s thyroid. Evidence shows that even the earliest signs of autoimmune thyroid disease in the mom can raise the baby’s risk for neurological issues like autism¹.

Early in pregnancy, the fetus cannot make thyroid hormones and depends on those from the mother. If mom has enough then the baby does as well. If mom is on thyroid medication, it may need to be adjusted because the baby is also using these hormones. When mom is taking thyroid meds, extra iodine is not needed.

But during the second trimester, the baby’s thyroid starts to work. By the third trimester, the fetal thyroid is fully active. At this point, the fetus needs its own supply of iodine to do so.

If mom is iodine deficient, this is when the most problems emerge. The baby can be born with cognitive delays and poor brain development. More severe deficiencies can cause babies to be born with cretinism – severe abnormalities in brain and skeletal development. They can also be formed with a near complete lack of thyroid function called congenital hypothyroidism.

Some statistics suggest that 10-16% of pregnant women may be low enough in iodine to be at risk for such problems.

Yet many researchers have noticed a paradox. Even though many are at risk, iodine deficiency issues have not occurred for some time. The most recent was in rural China in the early 1990s. Before then the most recent was in the 1960s in Papua New Guinea³.

Who is most at risk for iodine deficiency? Moms who are:

• Vegan
• Not on thyroid medication
• Not prone to thyroid disease

Populations who are mildly to moderately ‘iodine deficient’ do not have higher rates of cognitive or developmental delays⁴.

The question of much research has been If many people are ‘iodine deficient’ why do so few develop iodine deficiencies?

It seems that iodine is needed, but in lower amounts than we used to think. It is also getting clear that pregnant women are more at risk from too much iodine than was thought before. In fact, the few modern cases of congenital hypothyroidism came from moms who were taking high doses of iodine in pregnancy⁵.

How Much Iodine Does a Pregnant Woman Need?

Older guidelines suggest that women should consume between 150 to 300 mcg per day from all sources combined. The World Health Organization suggests this range with a safe upper limit of 500 mcg per day.

Yet the iodine window seems to be narrower, even for pregnant women.

New research suggests 500 mcg is far too much, 250 mcg/d might be a safer upper limit⁶.

“the risks of even mild iodine excess in pregnancy need to be carefully considered. The lowest prevalences of hypothyroidism, hypothyroxinaemia, and thyroid autoimmunity, as well as the lowest serum thyroglobulin levels observed in the women with UIC of 150–249 µg/l⁷“

It seems that for pregnancy and lactation, women should consume about 150 – 250 mcg of iodine per day. It is worth pointing out that the study referred to 150-249 as the amount of iodine in urine which is close to, but not identical to daily intake.

If moms are on thyroid medications, their iodine requirements are lower because their medications contain enough iodine for mom’s own requirements. In those cases, 100 – 200 mcg per day is a better range.

What Does That Mean in Terms of Daily Intake?

What do those amounts mean in terms of typical foods? All foods contain some iodine. Some foods have consistent amounts of iodine. The amount in many processed foods can be highly variable.

To get a stable amount of iodine during pregnancy and not get too much, the best approach is to regularly consume foods that have a moderate amount and are not prone to significant fluctuations in iodine.

In the Thyroid Reset Diet, I divided foods into 3 categories by their iodine intake. Green light foods are consistently low in iodine with rarely over 10 mcg per serving. Yellow light foods consistently have 10-50 mcg per serving. Red light foods commonly have well over 50 mcg per serving.

Because all foods have some iodine, there is a baseline intake of about 50 – 100 mcg that is hard to get below, even if one only consumes green light foods.

In order to reach the goals of 150-250 mcg per day, pregnant and lactating women should consume 1 or 2 servings of yellow light foods each day. For those on thyroid medication, 1 serving per day is best.

Examples include:

• Greek yogurt, unsweetened – 4 ounces
• Potato with skin – 1 potato
• Navy beans, canned and salted 1/2 cup
• Prune juice – 4 ounces
• Pineapple juice – 4 ounces
• Sunflower seeds, roasted and salted (commercial) – 1 ounce
• Spirulina – 2000 mg
• Chlorella – 2000 mg
• Egg yolk – 1

More food options can be found in the food lists in the Thyroid Reset Diet.

Taking Iodine Supplements During Pregnancy

What about iodine supplements during pregnancy?

One big problem with this approach is that the amount of iodine actually in prenatal supplements is not what the labels suggest.

One recent study analyzed many popular prenatal vitamins. Some were prescription and some were over the counter. NONE had close to the labeled amount of iodine. Many had several times more than they were supposed to contain⁸.

Some that were labeled as having 226 mcg actually had 610 mcg or more than twice the day’s safe intake. It is far better to get iodine from dietary sources.

Given the narrow range of iodine requirements, supplements are not a good solution. The amount of iodine they contain is just too unpredictable.

What do medical organizations say about iodine supplements in pregnancy?

• Roughly 75% of obstetricians and midwives do not recommend iodine supplements for preconception, pregnancy, or lactation⁹
• The American College of Obstetricians and Gynecologists does not recommend iodine supplementation
• The American Academy of Clinical Endocrinologists do not recommend iodine supplementation outside areas with endemic iodine insufficiency¹⁰
• The American Thyroid Association states:

“Without specific physiologic evidence of iodine deficiency in the United States at this time, and with the most recent U.S. survey reporting a median value of 173 g/L, which is within that currently recommended for pregnancy, the rationale for iodine supplementation during pregnancy is tenuous^11″

The Cochrane Group is renowned for unbiased reviews of important medical issues. Recently they examined the medical literature to see if iodine supplementation during pregnancy was helpful.

After carefully reviewing all high-quality studies they found that it was not. It turned out that iodine supplements used during pregnancy had no clear benefits and many side effects.

They stated that iodine supplementation during pregnancy¹²:

• May worsen nausea and vomiting
• May elevate maternal thyroid antibodies
• Has no clear effect on maternal thyroid disease
• Did not affect the rate of preterm births
• Did not affect the babies’ risks of thyroid disease

Iodine is complicated. We need some, but many people can’t tolerate too much. For those with thyroid disease, it takes planning to avoid too much.

More iodine is needed during the later stages of pregnancy. But it turns out that the additional amount needed is less than we thought before and even lower for those on thyroid medications.

Iodine supplements are not good to rely on because the amount of iodine they truly contain is not clear. Food sources are the best way to safely increase to the best levels. Thankfully many foods have moderate amounts of iodine and these are easy to include in a healthy diet.

P.S. Whenever you are ready, here is how I can help you now:

1. Schedule a Thyroid Second Opinion with me, Dr. C, Click Here for Details
2. Need A Thyroid Supplement Recommendation? Take My Thyroid Specific Formulations Quiz Now
3. Need a Personalized Supplement? Check out My Thyroid Specific Formulations
4. Download and use my Favorite Recipes Cookbook Here
5. Check out my podcast Medical Myths, Legends, and Fairytales Here

Dr. Alan Glen Christianson (Dr. C) is a Naturopathic Endocrinologist and the author of The NY Times bestselling Adrenal Reset Diet, The Metabolism Reset Diet and The Thyroid Reset Diet.

Dr. C’s gift for figuring out what really works has helped hundreds of thousands of people reverse thyroid disease, lose weight, diabetes, and regain energy. Learn more about the surprising story that started his quest.