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We know that what we eat makes a big difference to our thyroid gland, the small, butterfly-shaped gland at the base of the neck. Indeed, we hear a lot about what we should eat versus what we shouldn’t eat. But, one thing that may surprise you is that certain types of vegetables may not be so helpful for your thyroid. Indeed, they may exacerbate your thyroid dysfunction, especially when consumed in large quantities or cooked incorrectly. Ahead is what you need to know about cruciferous veggies and an underactive thyroid (hypothyroidism).
The term “goitrogen” refers to something that causes the thyroid to enlarge (goiter). In the context of nutrition, goitrogens are naturally-occurring plant-based compounds found in certain vegetables and some fruits. These compounds interfere with healthy thyroid function, making it harder for the thyroid gland to do what it needs to do to fulfill its role in the body.
Goitrogens are divided into three groups:
Goitrins and thiocyanates emerge in foods when damaged, such as through cooking preparation and even chewing. Flavinoids are often considered antioxidants for health benefits, but once gut bacteria break them down, they can become goitrogenic.
Eating too many goitrogens could interrupt your thyroid function through various mechanisms if you have hypothyroidism. However, with that said, people with normal thyroid function are usually not susceptible to the goitrogenic effects of these foods.
Perhaps the most prevalent way goitrogens affect the thyroid is to prevent iodine from entering the thyroid gland. The thyroid needs iodine to make thyroid hormone, and an iodine deficiency is one possible risk of hypothyroidism.
When the hypothalamus in the brain senses that T4 and T3 levels are insufficient, it stimulates the pituitary gland to release more TSH (thyroid-stimulating hormone), signaling the thyroid to make more thyroid hormone. If the thyroid cannot keep up with this demand, it grows larger, becoming a goiter.
May interfere with TPO enzyme function
Thyroperoxidase (TPO) is an enzyme that helps iodine attach to tyrosine, and this process is crucial for thyroid hormone production. So just like goitrogen’s ability to interfere with iodine uptake by the thyroid, interfering with TPO enzyme function may signal to the hypothalamus that more TSH is required to boost thyroid hormone production.
May reduce T4 absorption
Some soy-based or soy-enriched foods also have goitrogenic compounds. Studies show that soy may reduce T4 absorption and interfere with thyroid hormone action in cells. This interference can alert the pituitary that more TSH is needed to stimulate thyroid hormone production to satisfy cellular needs.
When the thyroid is signaled to make more thyroid hormone, it responds to constant increased demand by making more cells to help produce more thyroid hormone. This increase in cells leads to an increase in thyroid size, ultimately leading to a goiter. Goiters are not only a sign of a malfunctioning thyroid but can make breathing and swallowing more challenging because they cause the throat to feel tighter and more restricted.
Goitrogenic-rich foods mostly fall under the category of cruciferous vegetables.
Cruciferous veggies are highly popular for their health benefits. Loaded with fiber, vitamins, and minerals (not to mention low in calories), these superfoods are an ideal addition to your daily nutrient intake. Cruciferous vegetables come in various colors. However, cruciferous veggies that are dark green often contain phytonutrients, which are plant compounds that could reduce inflammation and decrease your risk for certain cancers.
One of the additional benefits of cruciferous vegetables is that they help you feel full without too much intake. Thus, it is a popular choice for people to boost their health and control weight gain and satiety issues. Between 1 to 2 cups of raw or cooked cruciferous veggies are sufficient to help you meet your daily vegetable serving requirements.
Some of the most potent goitrogenic foods happen to be cruciferous vegetables, such as:
- Bok choy
- Brussels sprouts
- Collard greens
- Mustard greens
Goitrogens are also in other food categories, including some fruits (pears and strawberries), starchy plants, and soy-based foods.
Before veggies take the blame for interrupting thyroid function, know that there are many chemicals in our environment and even in medications considered goitrogens. However, cruciferous vegetable intake tends to be the biggest offender when consumed in large quantities if you have a thyroid condition.
So, how do you get the benefits of eating your greens without interrupting your thyroid hormone levels? Well, a lot of it comes down to how you prepare your food. The fact is that cruciferous vegetables offer numerous health benefits, and their potential to lower inflammation is appealing to people struggling with an autoimmune thyroid disease like Hashimoto’s disease. Aside from inflammation, these vegetables are packed with antioxidants, fiber, essential vitamins like vitamin K, and minerals.
The key to getting the benefits of cruciferous vegetables lies in how much you eat of these foods and prepare them. When preparing cruciferous vegetables, it helps to cook all of your veggies instead of eating them raw. Steaming or sauteing vegetables can help break down compounds that may cause goitrogenic activity.
Next, you can also blanch your leafy greens like spinach and kale. Blanching followed by freezing your vegetables can make an excellent addition to your smoothie without overly compromising your thyroid function if you like to have smoothies.
Lastly, make sure you incorporate a lot of variety in your diet. Eating only leafy greens to get your vitamin, mineral, and fiber intake is not the way to go, especially if you have hypothyroidism. So, suppose you are a daily green smoothie drinker. In that case, you may benefit from switching it up to only doing that once or twice a week and opting for different smoothie ingredients the other days.
A final note from Paloma Health
Those whose diets contain adequate iodine (which is most of us in iodine-sufficient countries like the United States) can safely consume these vegetables in reasonable amounts, especially when cooked. Consult with a thyroid nutritionist to develop a personalized nutrition plan that meets your unique needs.