The thyroid is a small, butterfly-shaped gland at the base of the neck responsible for many of the body's metabolic functions. The thyroid may become swollen for a number of reasons including autoimmune thyroid disease, insufficient dietary iodine, certain pharmaceutical drugs and during pregnancy or lactation. Goitrogenic foods contain substances which prevent the thyroid from absorbing iodine – crucial to its production and conversion of thyroid hormones T4 and T3 – which can cause or worsen a swollen thyroid.
Soy may be the No. 1 food culprit for a swollen thyroid, according to to Dr. Eric Osanski. Soy contains goitrogenic compounds which interfere with the absorption of iodine. Soy was linked to thyroid dysfunction in rats, particularly when iodine deficiency was present, according to research published in the “Environmental Health Perspectives” in June of 2002. According to the University of Maryland Medical Center, soy may also interfere with the absorption of thyroid medications.
Millet, a grain that isn't consumed on a large scale in this country, is considered a powerful goitrogen and should be avoided during acute thyroiditis. Research published in the “Annals of Nutrition and Metabolism” revealed that traditional fermentation actually increases the goitrogenic activity of millet. While most grains aren't considered true goitrogens, many experts including the UMMC recommend avoiding wheat if you have a swollen thyroid. This may be because of the direct link between gluten intolerance and autoimmune thyroid disease, according to research published in “Clinical Medicine and Research” in 2007.
Vegetables and Fruits
Broccoli and other cruciferous vegetables contain goitrogenic substances when eaten or juiced raw, which can be limited by cooking. If you have thyroiditis or a goiter, you should avoid veggies like broccoli, cauliflower, kale, radishes, kohlrabi, mustard greens, rutabagas, bok choy and cabbage, particularly in their raw form. According to nutrition expert Chris Masterjohn, the goitrogens in cruciferous vegetables are not broken down by fermentation – steaming reduces them by about one-third, while boiling them for 30 minutes reduces them by about 90 percent. Certain fruits are considered mildly goitrogenic and include strawberries, peaches and pears.
It is not necessary to completely eliminate all goitrogenic foods from the diet for most people. The key is moderation; don't eat goitrogenic foods every day or at each meal if you are experiencing a swollen thyroid. Be sure to eat cruciferous vegetables that have been well-cooked. Avoid the green smoothies and opt instead for fresh juices made from non-goitrogenic fruits and veggies.