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Is Low Thyroid Function a Reason to Avoid Eating Brassicas? - Blog Image

Is Low Thyroid Function a Reason to Avoid Eating Brassicas?

BY: Andrea Nakayama

DATE: 2018-05-17

Today I want to talk to you about one of my favorite topics…

Brassicas and Thyroid Function

As a nutritionist, I find it hard to refute the value of broccoli and its budding cousins, like kale and cabbage. Yet, there can be so much confusion about brassicas when it comes to thyroid health and wellness. In fact, one question that almost always comes up when I talk about these beneficial beauties with my clients is “should I avoid brassicas?” As a Functional Nutritionist, my answer is, as always, “it depends.”

What is a brassica?

When we refer to the brassica family, we’re speaking about those cruciferous vegetables you know, love and possibly fear. Those cruciferous, green leafy vegetables include:

  • broccoli

  • kale

  • Brussels sprouts

  • cauliflower

  • collard greens

  • mustard greens

  • broccoli raab

  • arugula

  • bok choy

  • Napa cabbage

  • and even some roots like radish, turnips, horseradish and wasabi

Brassica is simply the Latin name for this family of vegetables, basically meaning “cabbage”.

What nutrients do brassicas provide?

Brassicas are powerhouses of nutrients, which include vitamin C, vitamin K, the complex of B vitamins and carotenoids. So, why would a person avoid brassicas?

Brassicas are a perfect example of how one person’s food can be another person’s poison. I get it. This can be confusing. Although I cannot refute the nutritional benefits of brassicas, the goitrogens in the brassicas may do a person with thyroid issues more harm than good, depending on several key factors.

What is a goitrogen?

In addition to the nutrients mentioned above, brassicas also contain compounds known as goitrogens. Goitrogens can cause thyroid hormone deficiency under any of the following conditions:

  • if eaten in excess (an amount dictated by the individual, not the measuring cup)

  • in the presence of mineral deficiency, such as iodine

  • in the presence of mineral excesses, as is the case with calcium or fluorine

Should you avoid brassicas?

Many experts would say that it’s nearly impossible to consume enough goitrogens to become a real problem unless the foods highest in this plant chemical—turnips and rutabagas—are eaten daily, as a dietary staple, and in the presence of iodine deficiency.

But of course, we are all unique beings. This is one of the most important tenets of Functional Nutrition! Meaning, we each have different mineral stores and shortages. Therefore, a person’s proximity to the healing or harmful effects of any food or practice differs and depends. As the teacher of thousands of aspiring Functional Nutrition Counselors, I’d be remiss if I did not speak this truth. 

That said, because of their rich and beneficial antioxidant and fiber content, I do not recommend (nor do I practice, as someone with a thyroid disorder) brassica avoidance.

More food for thought

It is commonly believed that cooking helps to dissolve and inactivate the goitrogens in brassicas, though there is no clear evidence about the amount of heat or the time exposed to the heat that will do this.Even so, cooking and moderate consumption should enable you to reap the nutritional benefits of brassicas, inviting the friend and forsaking the foe. Whew!

Final Verdict

So, can I keep eating brassicas even with my diagnosed thyroid issues? Indeed I can, and you can too. As a Functional Nutritionist, I’m a fan of all brassicas – particularly for their liver loving life force. In terms of health benefits, they are nearly unrivaled as a food source for activating glutathione (the mother of all antioxidants) and supporting detoxification of many chemical substances through the liver. So here’s the good news, bring on the broccoli and keep eating those brassicas!

Favorite brassica supportive resource:
Mapping Sulforaphane with Tom Malterre on the 15-Minute Matrix


Quirante-Moya S, García-Ibañez P, Quirante-Moya F, Villaño D, Moreno DA. The Role of Brassica Bioactives on Human Health: Are We Studying It the Right Way?. Molecules. 2020;25(7):1591. Published 2020 Mar 30. doi:10.3390/molecules25071591

Soengas P, Velasco P, Fernández JC, Cartea ME. New Vegetable Brassica Foods: A Promising Source of Bioactive Compounds. Foods. 2021;10(12):2911. Published 2021 Nov 24. doi:10.3390/foods10122911

Ağagündüz D, Şahin TÖ, Yılmaz B, Ekenci KD, Duyar Özer Ş, Capasso R. Cruciferous Vegetables and Their Bioactive Metabolites: from Prevention to Novel Therapies of Colorectal Cancer. Evid Based Complement Alternat Med. 2022;2022:1534083. Published 2022 Apr 11. doi:10.1155/2022/1534083

Babiker A, Alawi A, Al Atawi M, Al Alwan I. The role of micronutrients in thyroid dysfunction. Sudan J Paediatr. 2020;20(1):13-19. doi:10.24911/SJP.106-1587138942

Andrea Nakayama

By: Andrea Nakayama, FxNA Founder & Functional Medicine Nutritionist

Functional Nutrition Alliance provides the comprehensive online Functional Nutrition training in the Science & Art of the Functional Nutrition practice. Learn to address the roots of your clients’ suffering with client education, diet & lifestyle modifications.


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