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Thyroid Diet: How To Eat with a Thyroid Disorder

Is there a thyroid diet? Four key points on how your food choices can impact your thyroid status and your overall health, according to thyroid experts.

With Angela M. Leung, MD, MSc

“At the American Thyroid Association annual meeting, we presented in a session on Iodine and Thyroid Health, about the potential effects that dietary modifications can have on the thyroid,” says Angela M. Leung, MD, MSc, assistant clinical professor of medicine at UCLA School of Medicine in California.

Despite having a thyroid disorder, cruciferous vegetables are beneficial given their antioxidants and high fiber.Even for people with a thyroid disorder, including cruciferous vegetables should be included as part of a balanced, healthy diet. Photo: 123RF



“We summarized that adequate iodine nutrition of 150 mcg a day is essential for normal thyroid function but that an excessive intake—be it from a variety of sources (eg, fortified salt, supplements, seaweed, seafood)—can have the reverse effect: too much iodine can cause hypothyroidism and hyperthyroidism and too little iodine low may lead to hypothyroidism,” Dr. Leung says.

“It’s important to remember that you are more than your thyroid disease, so you’ll want to eat a well-balanced diet to support your overall health needs,” Dr. Leung tells EndocrineWeb. Too much, as well as too little, of any essential nutrient, may lead to more health problems, complicating your thyroid status rather than improving it.1

Understanding the Ways Diet Affects Thyroid Function

The thyroid gland is prompted to release thyroid hormones into the blood by thyroid stimulating hormone (TSH). When the thyroid doesn’t respond properly, you may develop either hypothyroidism or hyperthyroidism.

The vast majority of individuals—one in seven are women—with hypothyroidism in the US have Hashimoto’s thyroiditis, an autoimmune disease in which your body doesn’t produce enough thyroid hormone, but this isn’t caused by iodine levels in the diet.2 Other less common causes of hypothyroidism include a deficiency of iodine in the diet, taking certain medications that interfere with thyroid absorption, surgical removal of the thyroid, and a genetic disorder. 

1. Focus On How to Eat Enough Vegetables, Not Which Ones to Avoid

“We talked about eating cruciferous vegetables like kale, broccoli, cauliflower, bok choy, which may have the effect of depleting the thyroid of getting enough iodine,” says Dr. Leung.  Any issue with iodine update may be due to the presence of thiocyanates in this food group.

Eating too much of these vegetables could be a problem for people who don’t get enough dietary iodine and too little selenium since a lack of both of these minerals can increase the risk of forming goiters.2

And yet, the level of thiocyanates varies substantially, even in different varieties of a single food. Take kale, the level of thiocyanates in a serving can vary from zero to 400 mm/kg based on fresh vegetable weight .3

If you have hypothyroidism or a family history of goiters, you can reduce your risk by mixing up your choice of vegetables so you aren’t eating a lot of the same vegetable day in and day out, cooking your vegetables and chewing them thoroughly which helps to break down the worrisome substances, says Dr. Leung. And, it wouldn’t hurt to avoiding eating cruciferous vegetables raw; even lightly steaming then will deactivate the thiocyanates enough to assure that you aren’t eating more than your thyroid can handle.3

Another reason to lessen your concerns about these so-called goitrogenic foods is that the thiocyanate levels vary even by the type of kale, for example, for which there are more than a dozen varieties.4

The amount in broccoli, cabbage, and kale in a usual diet is considered of minimal risk. For example, there was no adverse effect on thyroid function from consuming five ounces of cooked Brussels sprouts every day for four weeks.5,6 One note of caution, if you have a thyroid disorder, it's important to realize that juicing concentrates the amount of thiocyanate, on the order of  2000 mcg per glass.7

To offer some perspective: up to 95% of the thyroid hypothyroidism in the US is caused not by an iodine deficiency, but occurs as the result of an autoimmune disease so avoiding cruciferous vegetables will do little to fix your underactive thyroid, and may deprive you of  valuable healthy benefits such as dietary fiber, and anti-inflammatory, cancer-fighting antioxidants.5

If that’s not enough to calm your concerns, some experts suggest that eating cruciferous vegetables may actually be beneficial if you have autoimmune hypothyroidism since the thiocyanates may slow the absorption of iodine in people getting too much, which is possible if you are eating a typical Western diet of fast foods, French fries, and other processed products, that contain iodized salt, and you are heavy-handed with the salt shaker.

A Quick Comment About Soy

The isoflavones in soy-based foods (eg, tofu, soy milk and soy protein, tempeh, edamame, miso) can inhibit thyroid peroxidase (TPO), an enzyme involved in the production of thyroid hormones.8

When an autoimmune thyroid disease such as Hashimoto’s thyroiditis or Graves’ disease is suspected, your doctor may do a TPO test to check for antibodies, which will help in diagnosing the reason for your thyroid disorder.

“Eating too much of these types of [soy-containing] foods might lead to a depleted thyroid hormone level, but the chance of this happening, or the likelihood that most people will reach a dangerously high intake that would present a problem, is likely very low,” Dr. Leung tells EndocrineWeb.

2. Resist the Temptation to Follow Headlining Diets

Do yourself a favor, “resist the temptation to jump on the bandwagon of popular, headlining diets like the Leaky Gut, Gluten-Free, or Paleo,1 says Dr. Leung.

Risks may arise when you eliminate whole food groups, or worry about avoiding specific foods (ie, soy, cruciferous veggies, gluten) is not the answer to thyroid health. It’s far more important that you focus on eating for your general well-being rather than following a diet that won’t necessarily support a healthy thyroid.

“In the absence of strong scientific data supporting the association of most of these popular diets with thyroid disease, patients should be reassured that eating a well-rounded, balanced diet, and avoiding any unnecessary dietary restrictions offers the best strategy for overall health," she says.

3. Consider Nutritional Supplements a Cautious Last Resort

While you might think you are doing the right thing by taking a nutritional supplement, the bitter truth is you may be setting yourself for unknown harms instead. 

It is difficult to recommend supplements labeled for the purpose of promoting thyroid support since these may contain nutrients in high amounts, which actually could be harmful to the thyroid,” Dr. Leung says.

There are two exceptions:

  • "In mild Graves’ eye disease supplementation with selenium is recommended," says Dr. Leung.  
  • “For women who may become pregnant, during pregnancy, or lactating, the American Thyroid Association recommends taking a daily supplement containing 150 mcg of iodine,”8 says Elizabeth Pearce, MD, MSc, professor of medicine at Boston University School of Medicine in Massachusetts, and the ATA also recommends against taking added selenium during pregnancy given some concern that there is an increased risk of developing gestational diabetes.

It’s just as important to be certain that you aren’t getting too much iodide as not getting enough. The most effective way to protect yourself is to check the label of any supplement before you take it so you are fully aware of the nutrient levels promised.

Since nutritional supplements are not regulated to the same stringent level as medications, you’ll also want to find a trusted source for any supplement you do take, so you can have some certainty of what you are getting, as you want to avoid any unnecessary or undesirable filler ingredients.  For more on this read this EndocrineWeb article: Thyroid Supplements.

4. Finding the Dietary Rhythm that is Right for You

In effect, there is no single, specific diet or vitamin/mineral supplement that has been proven to eliminate thyroid disease, according to the National Center for Complementary and Alternative Medicine.  If you would like more guidance on the right diet to meet your individual needs, you can consider working with a registered dietitian who has a specialty in thyroid health, or an integrative medicine physician.

The main message from this session is that having a well-rounded, balanced diet that contains hopefully at least 150 mcg of iodine per day, especially those with dietary restrictions, such as vegans and ovolactovegetarians, is recommended.1  

However, there is little scientific evidence regarding some of the other dietary modifications that have been proposed and are widely popular on the internet, and these include taking extra iron and avoiding cruciferous vegetables,” Dr. Leung tells EndocrineWeb.

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