I want to know what foods decrease thyroid function are. i read that, for example, the peanut is one of them.

Thyroid and food: Non-fermented soy products ( tofu, soybeans) can inhibit thyroid function. Certain vegetables if eaten in large quantities could decrease thyroid function. These would include: broccoli,cabbage, spinach, cauliflower, lima beans, turnips, corn and sweet potatoes. Strawberries should be avoided and indeed peanuts and pine-nuts should also be avoided. These foods are known as goitrogens.