Is there a direct relationship between thyroid cancer and diet? There is no clear conclusion yet. Foreign epidemiological surveys show that there is a relationship between high iodine diet and the development of differentiated thyroid cancer (follicular and papillary carcinoma), while low iodine diet may induce the development of undifferentiated cancer. Therefore, deliberately high or low iodine is not good. Most of the thyroid gland remains after thyroid cancer surgery, or latent thyroid cancer cells cannot be excluded from the body. Long-term high iodine may stimulate the proliferation of normal thyroid follicles or thyroid cancer cells, while long-term iodine-free diet may also stimulate the production of undifferentiated cells. Therefore, in general, a normal diet is sufficient, and the basic amount of iodine can be maintained in most areas of China: 150-200ug/day. However, seaweed and nori contain very high amounts of iodine (240mg/kg), and eating very small amounts will exceed the requirement, so it is recommended to avoid them or eat them as little as possible. Iodized salt also does not contain much iodine, about 20-50ug/g, which is safe if less than 6g per day according to national regulations, but the daily intake in northern areas is much higher than 6g, so if you cannot reduce the amount of salt used, it is better to switch to non-iodized salt. Fresh sea fish, shrimp and sea crab meat contain about the same amount of iodine as land meat and poultry, about 100-600ug/kg, so they can be eaten in moderation without deliberate avoidance. Dried sea fish and dried shellfish contain slightly more iodine, about 800ug/kg, so do not eat more. Cauliflower, cabbage, purple kale and other cruciferous plants can hinder the absorption of iodine in the intestine, so do not eat them in large quantities for a long time either.