Foods That Can Affect Your Thyroid

All About Goitrogens and Cruciferous Vegetables

Close up of woman chopping vegetables
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Goitrogens are naturally-occurring chemicals found in various foods. Goitrogens have two ways they can affect your thyroid:

  1. Goitrogens can cause a goiter—an enlargement of your thyroid gland.
  2. Goitrogenic foods can act like antithyroid drugs, slowing down your thyroid, and ultimately causing hypothyroidism, an underactive thyroid.

Foods that contain goitrogens are able to disrupt your thyroid's function by inhibiting your body’s ability to use iodine. More specifically, goitrogens can block the process by which iodine becomes the key thyroid hormones thyroxine (T4) and triiodothyronine (T3). They also inhibit the actual release of thyroid hormone by your thyroid gland, and disrupt the peripheral conversion of the thyroid storage hormone T4 into the active thyroid hormone T3 (triiodothyronine).

If you have adequate levels of iodine in your diet, your thyroid can for the most part manage a diet that includes goitrogenic foods. In some cases, however, consuming high amounts of goitrogens on a regular basis may have an impact on your thyroid health.

Common Foods With Goitrogenic Ability 

The key goitrogen-rich foods are the vegetables in the cruciferous category. In addition, there are a number of other foods that contain significant amounts of goitrogens.

Some of the more common and potent goitrogens include the following vegetables, fruits, and other types of foods:

  • African cassava
  • Babassu (a palm-tree coconut fruit found in Brazil and Africa)
  • Bok choy
  • Broccoli
  • Broccolini
  • Brussels sprouts
  • Cabbage
  • Cauliflower
  • Chinese Broccoli
  • Collards
  • Daikon
  • Kale
  • Kohlrabi
  • Millet
  • Mustard
  • Peaches
  • Peanuts
  • Pine nuts
  • Radishes
  • Red Radish
  • Rutabaga
  • Spinach
  • Strawberries
  • Turnips
  • Watercress

Should You Eat Goitrogenic Foods? 

Goitrogenic foods are rich in vitamins and minerals, and most experts do not recommend that anyone—including patients with thyroid disease—avoid eating them. However, there are a few sensible guidelines to consider.

Substances found naturally in goitrogenic foods can slow down the production of thyroid hormone—keep in mind, though, this phenomenon occurs typically in people with an underlying iodine deficiency (which is rare in the United States). Still, even for people without iodine deficiency, experts recommend not over-consuming goitrogenic foods.

Steaming, cooking, or fermenting can reduce the levels of goitrogens in goitrogenic foods. With that, if you are concerned about exposure to goitrogens, limit the amount of raw goitrogenic foods you eat. An important note: Raw juicing often features goitrogenic vegetables like cabbage and spinach, and these juices end up providing highly concentrated amounts of goitrogenic chemicals. 

If you are hyperthyroid, a diet rich in goitrogens may actually help slow down your thyroid. (But note that any natural approaches to managing hyperthyroidism and Graves' disease should always be overseen by a physician.)

If you are hypothyroid due to thyroid surgery known as thyroidectomy—for example, you're a thyroid cancer survivor, or you've had your thyroid surgically removed due to a goiter or nodules—you don’t need to be particular about goitrogens.

If you are hypothyroid due to radioactive iodine (RAI) treatment for Graves' disease, you also don't need to be particular about goitrogens.

If you are hypothyroid and still have a partially functional thyroid—such as with Hashimoto's thyroiditis—be especially careful not to overconsume large quantities of raw goitrogenic foods. If you are a heavy consumer of cooked goitrogens, however, and have a difficult time balancing your thyroid treatment, you may consider cutting back on the amount of goitrogenic foods in your diet. You may also want to discuss whether you have sufficient iodine levels with your practitioner.

What About Soy? 

Soy falls into the category of goitrogens. While soy foods do not affect the thyroid gland in people with normal thyroid function and adequate iodine levels, they can interfere with the absorption of thyroid hormone replacement medication (just like fiber and calcium supplements can). This is why experts recommend that patients with hypothyroidism not necessarily avoid soy foods, but simply ensure they are taking their thyroid medication on an empty stomach. In some cases, the dosage of a person's thyroid medication will need to be adjusted if soy is regularly consumed.

There is some concern that consuming isoflavones, which is the active ingredient in soy, may trigger the transformation from subclinical to overt hypothyroidism in people with marginal iodine intake. Research, though, regarding this phenomenon is controversial and largely does not support it. Still, to be on the safe side, many experts recommend moderating soy intake and avoiding soy supplements, whether you have normal or low thyroid function.

A Word From Verywell

Like most things in life, when it comes to diet and your thyroid, moderation is your best strategy. Consider seeing a nutritionist and your doctor, though, if you are struggling to eat healthily and/or want to evaluate your nutritional status, like whether your iodine levels are sufficient.

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