List of foods that people with hypothyroidism must avoid Symptoms of hypothyroidism, commonly known as hypothyroidism, is a disease caused by a lack of thyroid hormone in the body. People with hypothyroidism need to make dietary adjustments and avoid certain foods that can worsen the problem. Here is a list of foods that people with hypothyroidism need to avoid. Avoid Too Much Iodine Iodine is an important component of thyroid hormones, but too much iodine may have a negative impact on your thyroid gland. Under normal circumstances, adults only need to consume 150 mg of iodine per day, while patients with hypothyroidism need more.