The Link Between Kale and Thyroid Health

kale in basket and on wooden table

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Kale is touted as a wonder food, and you can find it on menus everywhere. But there may be some concerns about consuming kale if you have thyroid disease.

Let’s take a look at closer look at this nutritional powerhouse of a plant.

What Is Kale?

The Latin name for kale is Brassica oleracea acephala. Kale is a member of the cruciferous family of vegetables. It is tough and bitter when eaten raw. Kale is a close relative of other cruciferous vegetables, including cabbage, broccoli, cauliflower, brussels sprouts, and collard greens. Kale has long leaves, either curly or smooth, and the leaves don’t form a unified stem or head.

Kale leaves can be green or purple. Kale is full of vitamins and minerals, and in particular, the antioxidant known as alpha-lipoic acid, which has been shown to have numerous health benefits.

Health Benefits of Kale

Raw kale provides the following nutrients:

In addition to being a nutritious, low-calorie food, a number of health benefits are attributed to consumption of vitamin and mineral-rich kale, which is high on lists of the world’s healthiest foods.

These benefits, include the following:

  • Healthy skin and hair due to high amounts of vitamins A and C
  • Helps with digestion
  • Lowers risk for heart disease
  • Improves bone health
  • Lowers risk of developing asthma
  • Lower glucose levels and improves blood sugar balance and insulin sensitivity
  • Prevent oxidative stress-induced changes in patients with diabetes
  • Helps decrease peripheral neuropathy in diabetics
  • Low energy density due to lower calorie/high water content
  • Helps prevent constipation, aids in digestion and promotes regularity
  • High in vitamin K (inadequate amounts of vitamin D can result in increased risk of bone fracture)
  • High in lutein, which helps protect eye health
  • May block the carcinogenic effects of grilling foods at high temps

The Potential Link Between Kale and Thyroid Function

Kale, as a cruciferous vegetable, belongs to a family of foods known as goitrogens, meaning that they have the potential, when raw and in larger quantities, to slow down the thyroid, and promote the formation of an enlarged thyroid (called a goiter).

That said, the exact amount of kale that can be consumed has not been well studied. Therefore, the exact amount that may cause an adverse reaction to thyroid patients is unknown.

Moreover, for the general population, the health benefits of kale far outweigh any risks to the thyroid, and consuming some kale as part of the diet is considered safe and nutritionally beneficial.

In addition, in people with thyroid disease, the risks of making a thyroid condition worse are also minimal, as long as the kale (or any cruciferous vegetable) is not over-consumed.

It's important to note, however, that consuming raw kale and juicing kale may be a concern. Juicing raw kale makes the overall concentration of goitrogenic chemicals in the kale high. So, if consumed regularly, raw kale juice has the potential to adversely affect thyroid function, by inhibiting absorption of dietary iodine.

A Word From Verywell

In the end, if you have a thyroid condition, you may want to avoid or significantly limit intake of raw kale or raw juicing of kale and other goitrogens. Instead, opt to steam or cook cruciferous vegetables, as most of the goitrogens are completely destroyed by heat (so can be safely consumed in moderation). 

It's also sensible to keep a food diary, so you can record your consumption of kale (and how it's prepared). Then, be sure to bring your food diary to your doctor's appointment to ensure you are both on the same page. 

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Article Sources
  • Bajaj JK, Salwan P, Salwan S. Various Possible Toxicants Involved in Thyroid Dysfunction: A Review. J Clin Diagn Res. 2016 Jan;10(1): FE01-FE03.