Antithyroid medications such as methimazole and propylthiouracil are used to prevent the thyroid gland from making too much thyroid hormone. Excess thyroid hormone causes an overactive thyroid and a disorder known as hyperthyroidism. Symptoms of hyperthyroidism include weight loss, increased appetite, sweating, rapid heartbeat, goiter, insomnia and increased sensitivity to heat. Patients taking antithyroid medications should avoid certain foods.
Antithyroid hormones lower white blood cells, which makes it hard for patients to fight infections, according to the University of Michigan Health Systems. White blood cells fight disease-causing microorganisms that are introduced to the body. Patients with lowered white blood cell counts due to taking antithyroid drugs should reduce their intake of foods that contain high levels of bacteria, such as raw milk, blue cheese and other cheeses with mold, raw vegetables, raw fruits, pre-cut fruits, undercooked meat, sushi, raw oysters and yogurt.
Antithyroid medications increase the risk of internal bleeding, according to the University of Michigan Health Systems. Patients taking methimazole and propylthiouracil should avoid alcoholic beverages. Alcohol irritates the lining of the stomach and esophagus and increases the risk of bleeding.
Antithyroid medications make the thyroid less active, which leads to a slowed metabolism. Patients should therefore avoid overeating and consuming fattening foods to avoid excessive weight gain. Examples of fatty foods to be consumed in moderation include fried foods, bacon, hot dogs, sausages, whole milk, steak, cheese, butter, margarine and cream.