Boy do I love kale! In fresh juice, green smoothies, or massaged with lemon in a salad. I could probably eat kale with every meal, and some days I have. I also love cabbage, broccoli, cauliflower, and collards. But all of these cruciferous vegetables, along with a few other foods, have a potentially dangerous side effect when we go overboard.

Trouble in Paradise

Those cruciferous vegetables, along with soy and a few other foods, contain goitrogens. Goitrogens can adversely affect the thyroid. Some interfere with the thyroids ability to absorb iodine, while others create antibodies to the thyroids substances. These interactions reduce the thyroids production of hormones, which messes with our metabolism, big time.

The good news is that in a person with a healthy, normal thyroid, eating goitrogen-containing foods will usually just trigger the thyroid to produce more hormones to make up for the interference. But if you have a thyroid condition, especially hypothyroidism, eating foods that contain goitrogens can make it worse. And the jury is still out about eating large amounts of goitrogenic foods on a daily basis.

The foods that contain the most goitrogens include broccoli, broccolini, kale, collard greens, bok choy, Brussels sprouts, mustard, rutabaga, and most other vegetables in the brassica family. Brussels sprouts seem to be particularly dangerous because they are highest in nitriles, a substance that produces cyanide in the body.

Interesting side note: all of the brassica vegetables have been cultivated from different parts of the same wild broccoli ancestor plants. Thats why they offer similar health benefits and potential challenges.

There is also a relatively small amount of goitrogens present in spinach, peanuts, strawberries, millet, pine nuts, peaches, and cassava root.

The challenge with avoiding these plant foods is that they are very good for us for other reasons, and tend to make up the bulk of a healthy vegan diet. They contain many beneficial nutrients, including calcium, vitamins C and K, and beta-carotene.

Whats a Kale Lover to Do?

Until more research is done, it is recommended to eat foods that contain goitrogens in moderation. Cooking and steaming greatly reduce the goitrogenic activity in these foods, while fermenting does not. Juicing concentrates the goitrogens.

All good things in moderation. Variety is the cornerstone of a healthy diet. Most experts believe that goitrogenic foods will not cause a thyroid condition, but unfermented soy is suspect because it also contains thyroid-altering isoflavones.

As the main problem with goitrogens is that they interfere with iodine absorption, eating more iodine-rich foods can help if you have a normal thyroid. Foods that supply iodine include sea vegetables such as kelp, kombu, and dulse, potatoes, and cranberries.

So kale and I are still friends, as I have a normal thyroid. But I no longer have it three times a day. I also started eating more dulse and sprinkling some kelp flakes in my smoothies. And I am more likely to change up my smoothies and juices by using romaine lettuce, celery, cucumber, carrot, or some of the many other non-goitrogenic vegetables. Variety keeps our bodies healthy, and enjoying the good stuff in moderation makes for the most sustainable diets.