There is also considerable debate over goitrogens, which can impair thyroid gland function. Cruciferous vegetables like bok choy, broccoli, Brussels sprouts, cauliflower, collard greens, and fruits like peaches, pears, plums, raspberries, and strawberries are examples. These foods contain compounds called goitrogens that can interfere with how well your thyroid gland functions. The best way to avoid toxic substances is by eating a healthy diet full of nutritious food choices. However, if you cannot eat everything else, then it is recommended that you limit your consumption of these eight fruits. These are the eight worst fruits for your thyroid gland: raspberries, blackberries, blueberries, mulberries, cranberries, tomatoes, and potatoes. Of these eight plants, seven are identified as noxious weeds by the USDA. This means that they can cause or contribute to health problems if they are ingested. The only exception is tomato products which are safe to eat in small quantities. Tomatoes are high in potassium but also contain chemicals that can overload your thyroid gland with iodine. This can lead to thyroid dysfunction - especially if you are pregnant or planning to become pregnant soon. Iodine is needed for normal thyroid function but too much of it can be harmful. Therefore, it is recommended that women who are pregnant or trying to get pregnant avoid eating tomatoes.