Do a little Googling, and you might turn up a page or two claiming that cruciferous vegetables can cause thyroid troubles. The truth is a little murkier. While it's true that these veggies contain compounds called glucosinolates, which might interfere with your body's production of thyroid hormones in high amounts, it's pretty unlikely that they'll harm your thyroid if you're eating normal-size servings. One case report in the New England Journal of Medicine highlighted the story of an 88-year-old woman who showed up to the ER with hypothyroidism after eating about 2 or 3 pounds of bok choy a day—but, as Ilic points out, "that's not a normal amount."

Major diagnostic and therapeutic advancements in the early 20th century dramatically changed the prognosis of hypothyroidism from a highly morbid condition to one that could be successfully managed with safe, effective therapies. These advancements dictated treatment trends that have led to the adoption of l-thyroxine monotherapy, administered at doses to normalize serum thyroid-stimulating hormone (TSH), as the contemporary standard of care (Figure). Most patients do well with this approach, which both normalizes serum TSH levels and leads to symptomatic remission (1).


Rather than giving Synthroid (T-4) alone, Dr. Weil prefers combinations of the two natural hormones (T-3 and T-4), and often recommends the prescription drug Thyrolar. Under normal conditions, the body can convert T-4 into T-3; however, there is some question whether the body can do this optimally when under extreme physical or emotional stress. Giving a combination seems to elicit a more natural response for the body, and may also have a better effect on mood than T-4 alone.

One root vegetable that is the exception, and which can negatively impact an underactive thyroid is cassava, a common staple in certain parts of Africa. This plant “is known to produce toxins that can slow an already underactive thyroid,” Dr. Nasr says. But, “that’s not relevant here in the United States, unless you cook cassava and you eat it every day.”
Do you see “gluten-free”, “dairy-free” etc. popping up at the health stores today? This is because many people get off the “big five” (gluten, dairy, corn, eggs and soy) and experience significant changes. To find the culprits, I always start off with an Elimination Diet (I teach how to do the Elimination Diet at this free workshop) and this produces clear, unbiased results. You can also get a food intolerance test (not allergy; it’s different) done but they are far from accurate. Gluten is an infamous food for contributing to thyroid conditions, and eliminating it is key. However, often times, you would need to cut out more than just gluten if you wish to shape your diet for thyroid fitness.
l-Thyroxine monotherapy for athyreotic rats results in a high T4:T3 ratio at doses sufficient to normalize serum TSH levels (8). Yet, the brain, liver, and skeletal muscle tissues of these l-thyroxine–treated animals continue to exhibit markers of hypothyroidism (9), probably because of the inability of l-thyroxine monotherapy to restore tissue levels of T3 (8). This is probably a direct consequence of lower serum T3 levels and the relatively high T4 concentration in these tissues, which inactivates the type 2 iodothyronine deiodinase (D2). In the hypothalamus, loss of D2 is minimal in the presence of T4, which increases sensitivity to T4 levels and explains TSH normalization, despite relatively lower levels of serum T3. Only combination therapy with l-thyroxine plus l-triiodothyronine normalized all thyroid hormone–dependent measures (9), including serum and tissue T3 levels (8). Whether tissue-specific markers of hypothyroidism are restored with l-thyroxine monotherapy in humans remains to be determined, as does the ability of l-thyroxine plus l-triiodothyronine combination therapy to normalize the serum T4:T3 ratio without adverse events. The development of a novel drug delivery system for l-triiodothyronine would facilitate these studies (5).
But determining the correct dosage isn’t a quick process — you will need a blood test between six and eight weeks after you first start taking your medicine to see if your hormone levels are normalizing. If your doctor thinks you need a dosage adjustment, he or she will do so and recheck your hormone levels after another six to eight weeks. Once your thyroid hormone levels stabilize, you won’t need another thyroid check for six months. (5) Controlled hypothyroidism requires only an annual checkup. (3)
The thyroid gland is a 2-inch butterfly-shaped organ located at the front of the neck. Though the thyroid is small, it’s a major gland in the endocrine system and affects nearly every organ in the body. It regulates fat and carbohydrate metabolism, respiration, body temperature, brain development, cholesterol levels, the heart and nervous system, blood calcium levels, menstrual cycles, skin integrity, and more.1
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.

Hypothyroidism (overactive thyroid) is a condition in which the thyroid gland produces an abnormally low amount of thyroid hormone. Many disorders result in hypothyroidism, which may directly or indirectly involve the thyroid gland. Because thyroid hormone affects growth, development, and many cellular processes, inadequate thyroid hormone has widespread consequences for the body.


*Cassava bears special mention here.  You may have heard of it because it is the starchy root vegetable from which tapioca is made, but cassava is also a popular staple food in many Third World countries, where it is eaten boiled, mashed, or ground into flour.  Fresh cassava root contains a harmless substance called linamarin, which can turn into hydrocyanic acid (aka cyanide!) when the plant is damaged or eaten. Flaxseeds also contain linamarin. Cyanide is very toxic, so the human body converts it into thiocyanate (which, although it does interfere with thyroid function, is less toxic than cyanide and easier for the body to eliminate).
High-fat fried foods, like mozzarella sticks, jalapeno poppers and um…fried chicken and French fries can contribute to inflammation in the body, says Blum. Inflammation from Hashimoto’s disease, also known as chronic lymphocytic thyroiditis, often leads to an underactive thyroid gland. Hypothyroidism primarily affects middle-aged women, according to the Mayo Clinic, but it can target anyone at any age.

Like many people living with thyroid problems, you may wonder what the best thyroid diet to follow is. The truth is that the ideal diet for those who are living with a thyroid condition depends on personal needs and goals. If your goal is weight loss, you will want to optimize your blood sugar and leptin levels and eliminate toxins and allergens, among other things. If your goal is to support your thyroid health but not necessarily lose weight, there are some foods (such as goiter-producing vegetables and soy) that you may wish to minimize or avoid.

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Please Note: The material on this site is provided for informational purposes only and is not medical advice. Always consult your physician before beginning any diet or exercise program.

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