Kale and Your Thyroid: What You Need to Know

kale goitrogens goitrogenic vegetables cruciferous vegetables thyroid impact
Fresh Kale. Jane Frank/ Cookies and Curtains

Kale is touted as a wonder food, and you can find it on menus everywhere, and being touted in health magazines. But there may be some concerns about kale for people with thyroid conditions. Let’s take a look at kale, its health benefits, and what thyroid patients need to know.

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 has been eaten since Roman times and has been very popular in Europe for many years. 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.

The Health Benefits of Kale

Kale is a nutritional powerhouse, and one cup of raw kale (2.4 ounces) provides:

  • Vitamin A: 206% of the Recommended Daily Allowance (RDA) (from beta-carotene).
  • Vitamin K: 684% of the RDA.
  • Vitamin C: 134% of the RDA.
  • Vitamin B6: 9% of the RDA.
  • Manganese: 26% of the RDA.
  • Calcium: 9% of the RDA.
  • Copper: 10% of the RDA.
  • Potassium: 9% of the RDA.
  • Magnesium: 6% of the RDA.

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 grilling foods at high temps

The Kale and Thyroid Link

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 a goiter – an enlarged thyroid.

Consuming very large amounts of raw cruciferous vegetables has been shown to cause hypothyroidism in animals, according to the Oregon State University Micronutrient Information site, which states:

Very high intakes of cruciferous vegetables…have been found to cause hypothyroidism (insufficient thyroid hormone) in animals. There has been one case report of an 88-year-old woman developing severe hypothyroidism and coma following consumption of an estimated 1.0 to 1.5 kg/day of raw bok choy for several months.

One kilogram of a cruciferous vegetable like kale or bok choy would be about 15 cups – certainly not an amount most people are likely to consume. However, be aware of the potential for higher concentrations when juicing.

http://www.endocrineweb.com/conditions/hypothyroidism/news-update-can-kale-cause-hypothyroidism http://www.shape.com/blogs/weight-loss-coach/could-kale-cause-hypothyroidism 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 patients who already have a thyroid condition, the risks of making a thyroid condition worse are also minimal if kale (or any cruciferous vegetable) is not overconsumed.

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.

It appears that juicing kale may be a concern, however. Juicing raw kale makes the overall concentration of goitrogenic chemicals in the kale high. If consumed regularly, raw kale juice has the potential to adversely affect thyroid function, by inhibiting absorption of dietary iodine.

So thyroid patients may want to avoid or significantly limit raw juicing of kale and other goitrogens, and steam or cook cruciferous vegetables. Most of the goitrogens are completely destroyed by heat, so steaming or cooking these foods make them safe for thyroid patients to consume in moderation.

Here are a few links for thyroid-friendly kale recipes – all include cooked kale!

More Resources on Kale