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Do Cruciferous Vegetables Affect Your Thyroid?

Broccoli, cauliflower, and other cruciferous vegetables are sometimes said to interfere with thyroid function. Could eating these veggies cause low thyroid function?

By
Monica Reinagel, MS, LD/N, CNS,
Episode #368

Leena writes:

“I am a healthy 28-year-old with no medical issues but three of my siblings have hypothyroidism. I recently became aware that certain foods can have a negative effect on thyroid function, and I am a little concerned! Some of my favorite foods are on that list (broccoli, cabbage, millet). Can I still enjoy broccoli, cabbage, millet, and other veggies, without inducing hypothyroidism? Should I tell my siblings to stop eating these foods?”

Broccoli and cabbage are some of your favorite foods? Be still my beating heart!! Fortunately, Leena, I don’t think you or your siblings necessarily need to cut broccoli and other so-called goitrogenic foods out of your diet.

What Is a Goitrogen?

First, let me quickly explain why broccoli and other foods in the cabbage or brassica family are known as goitrogens. These vegetables contain a natural compound which, in large amounts, can interfere with your body’s ability to metabolize the mineral iodine.

Your body needs iodine in order to make thyroid hormone and if iodine is lacking—either because your diet is deficient in the nutrient or because something is inhibiting its uptake—your thyroid hormone levels can sink. When this happens, your thyroid gland can become enlarged; that’s your body’s way of trying to increase thyroid hormone production. An enlarged thyroid, which looks like a swelling in the neck, is known as a goiter.

The good news is that goiters caused by iodine deficiency can be easily reversed: Once iodine is added to the diet, the thyroid can produce enough thyroid hormone and the gland shrinks back to its normal size.

Goiters used to be much more common than they are today—and not because people ate more broccoli back then! Most goiters are caused by diets that are too low in iodine. Fortunately, since the advent of iodized salt, iodine deficiency is pretty rare these days.

What Causes Hypothyroidism?

Hypothyroid disease, especially the kind the runs in families, is not caused by iodine deficiency. It’s usually caused by an auto-immune condition where the body attacks and slowly destroys the thyroid gland. Once that happens, no amount of iodine is going to fix it. Instead, people with this type of thyroid disease take thyroid replacement hormone.

Even if you have thyroid disease in the family, eating goitrogenic vegetables does not increase your risk of getting it. And being treated for thyroid disease does not mean that these otherwise nutritious vegetables need to be off the menu. Assuming that your diet contains a sufficient amount of iodine, you—and your siblings—can eat these foods on a daily basis without worrying about interfering with your thyroid function.

But is it really possible to overdo it?

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