what foods support the function of the thyroid gland
1 Foods that can potentially lower thyroid activity are broccoli, cabbage, Brussels sprouts, cauliflower, kale, spinach, turnips, soy, beans, and mustard greens. 2  These foods may help if your thyroid gland is overactive (hyperthyroidism). 3  If it is underactive, ask your doctor if you should avoid these foods. These foods may help if your thyroid gland is overactive (hyperthyroidism). 2  If it is underactive, ask your doctor if you should avoid these foods. 3  Cooking deactivates some of the thyroid-lowering effects. 4  Use caution because people with thyroiditis can switch from hyperthyroidism to hypothyroidism very quickly.