Does Kale Slow Down Thyroid Function?

Do you have a thyroid condition? And, if so, were you told to stop eating your beloved Brussels sprouts, broccoli or other cruciferous veggies? The good news is you can bring those healthy and delicious superfoods back! Before we dive into this controversial topic, let’s start with a few definitions so we are all on the same page:

Hashimoto’s Thyroiditis:  an autoimmune form of thyroid disease in which the body’s immune system attacks the thyroid gland. This is actually the most common form of hypothyroidism today.

Goitrogens: foods that may contribute to the formation of a goiter, or enlargement of your thyroid by limiting iodine uptake and thyroid function. Cruciferous veggies fall under this category and include: broccoli, cauliflower, cabbage, Brussels sprouts and kale.

Outdated Concern:

In the past, practitioners warned patients with hypothyroidism against consuming cruciferous vegetables. The fear was that glucosinolate compounds present in these veggies interfered with iodine absorption, leading to goiter formation, which further reduced thyroid gland function. However, a decade of both animal and human studies have shown that cruciferous veggies do not negatively impact thyroid function EXCEPT in the case of a documented iodine deficiency. Iodine deficiency was a common cause of hypothyroidism in the 1950’s, but is rare today.

The Good News:

Cruciferous vegetables are popular, and for good reason. They’re a trend that’s here to stay due to their antioxidant and fiber-rich properties. From hormone balance to detoxification, they’re low-calorie superfoods that deserve a place on everyone’s table. Based on the research, as long as your iodine levels are sufficient, you are free to enjoy the many benefits of cruciferous veggies without worrying about decreasing thyroid function.

If you are unsure of your iodine status or still uneasy about including cruciferous veggies with the presence of hypothyroidism, try these suggestions:.

1. Consume the majority of your cruciferous veggies cooked instead of raw. Cooking them reduces the glucosinalate content that is largely responsible for the goitrogenic effect.
2. Limit the amount, initially, especially any that are raw (this includes juicing those vegetables as well).
3. Work on getting more iodine in your diet. We recommend getting iodine from plant sources versus iodized salt. Options include: kelp, sea veggies, dulse, nori, or kelp sprinkles (which add great flavor to savory dishes).

Resources:

1. Mcmillan, M., Spinks, E., & Fenwick, G. (1986). Preliminary Observations on the Effect of Dietary Brussels Sprouts on Thyroid Function. Human Toxicology, 5(1), 15-19.
2. Cho YA, Kim J. Dietary factors affecting thyroid cancer risk: a meta-analysis. Nutr Cancer. 2015;67(5):811-817.