Why should you not eat too much kale?

Answered by Douglas Hiatt

There are a few reasons why you might want to avoid eating excessive amounts of kale, although it’s important to note that this applies primarily to individuals who already have a thyroid problem or are at risk for developing one. Let’s delve into the details.

1. Goitrogens: Kale belongs to a group of vegetables called cruciferous vegetables, which also includes broccoli, cauliflower, cabbage, and Brussels sprouts. These vegetables contain compounds called goitrogens, which can interfere with the functioning of the thyroid gland. Goitrogens can inhibit the uptake of iodine by the thyroid, leading to the formation of goiter (an enlarged thyroid gland) and potentially affecting thyroid hormone production.

2. Thyroid hormone synthesis: The thyroid gland plays a crucial role in producing thyroid hormones, namely thyroxine (T4) and triiodothyronine (T3). These hormones are responsible for regulating metabolism, growth, and development in the body. However, excessive consumption of goitrogenic foods like kale can interfere with the synthesis of thyroid hormones, potentially leading to an imbalance in thyroid function.

3. Impact on iodine uptake: Iodine is an essential mineral required for the production of thyroid hormones. When goitrogens from kale are consumed in excess, they can compete with iodine for uptake by the thyroid gland. This can result in decreased iodine availability for thyroid hormone synthesis, potentially leading to hypothyroidism or an underactive thyroid.

4. Underlying thyroid conditions: If you already have an existing thyroid condition, such as hypothyroidism or Hashimoto’s thyroiditis, your doctor may advise you to limit your intake of goitrogenic foods like kale. This is because these conditions already affect thyroid function, and excessive consumption of goitrogens may exacerbate the problem. It’s always important to consult with your healthcare provider and follow their recommendations specific to your individual case.

5. Variety in diet: While kale is undoubtedly a nutritious vegetable packed with vitamins, minerals, and fiber, it is essential to maintain a diverse and balanced diet. Consuming excessive amounts of any single food, including kale, can lead to an imbalance in nutrient intake. It’s always beneficial to incorporate a variety of fruits, vegetables, whole grains, and lean proteins into your meals to ensure you receive a wide range of essential nutrients.

It’s important to note that the impact of goitrogens on thyroid function is primarily observed when consumed in large quantities or in individuals with pre-existing thyroid issues. For most people, consuming kale in moderation as part of a balanced diet is unlikely to have any significant negative effects on thyroid function.

As always, if you have concerns about your thyroid health or are unsure about dietary restrictions, it’s best to consult with your healthcare provider who can provide personalized advice based on your specific situation.