A large number of food contain anti-thyroid agents, collectively called  goitrogens. Goitrogens are substances that interfere with the uptake of iodine thus interfering the functioning of the thyroid. They also inhibit the transfer of iodine into mother's milk.

Many kinds of food are high in goitrogen, like vegetables of Brassica family: bok choy, mustard green, rape, rutabaga, turnips,  kohlrabi (German turnips), kale, cabbage, cauliflower, kai lan (Chinese broccoli, Brassica capitata var. alboglabra), brussels sprouts, arugula, horseradish, radish, wasabi and watercress. Also , pear, peaches, spinach, strawberry, tofu, soy products, pine nuts, peanuts, millet are high in goitrogens.

Goitrogens is de-activated in cooking heat. Eating raw vegetables high in goitrogens can cause hypothyroidism or hyperthyroidism.

There are incidences that long term eating too much raw vegetable have dangerously affected the functioning the thyroids.