Some foods have an effect on thyroid hormone production. Such foods should be avoided. Thyroid hormone production is inhibited by cabbage, cauliflower, sprouts, mustard greens, peaches, soybeans, spinach, and turnips. As a result, avoid eating them at all costs. If you are already having problems with hyperthyroidism, then these foods should be avoided even though they may not cause such problems for others. Cabbage has been known to inhibit the activity of an enzyme called tyrosine kinase which is needed for thyroid hormone synthesis. Cauliflower is similar to cabbage in this way so it should also be avoided by people who have hyperthyroidism. Likewise, other members of the brassica family such as broccoli, brussels sprouts, and kale contain high levels of glucosinolates which have the same effect on the body. People with hyperthyroidism should refrain from eating any of these vegetables because of this fact. Thyroid cancer is another issue that must be considered when eating cabbage. Theoretically, eating cabbage could trigger or accelerate such cancer growth but this has never been reported in medical journals. However, it is recommended that people with hyperthyroidism seek out medical advice before starting any new diets. It is important for their health and to prevent further damage to the thyroid gland from occurring.