Foods that should be included in a diet for an underactive thyroid include fish, seaweed and dairy, according to Everyday Health. Nuts such as hazelnuts and macadamia nuts are rich in selenium, which supports proper thyroid function.
Fish has selenium and omega-3 fatty acids, according to Everyday Health. Omega-3 fatty acids help to improve the symptoms of an underactive thyroid, and selenium is an important mineral that helps the body produce thyroid hormones, explains Healthgrades. Forty percent of people who suffer from an underactive thyroid have a vitamin B12 deficiency, and fish is rich in this vitamin.
In addition to selenium, seaweed is also a great source of iodine, which plays an important role in thyroid hormone production, reports Healthgrades. However, patients should talk to a doctor before increasing their iodine intake, as too much iodine may worsen thyroid disorders, explains Everyday Health.
Those with an underactive thyroid can also benefit from low-fat dairy products, explains Heathgrades. Dairy products such as milk and yogurt are rich in vitamin D, and research indicates that people suffering from hypothyroidism tend to be deficient in vitamin D, states Everyday Health. In addition, there is a link between vitamin D deficiency and Hashimoto's disease, which is a common cause of hypothyroidism.