Foods that provide selenium are thought to be helpful toward thyroid function. Dietitian Anne Collins suggests that you consistently eat selenium-rich foods such as whole-wheat bread, bran, Brazil nuts, tuna, onions, tomatoes and broccoli to help improve thyroid function.These foods are also high in other nutrients and fiber, which can contribute to overall health and weight management.hoto Credit Thomas Northcut/Digital Vision/Getty Images. Foods that contain good amounts of iron can improve thyroid function. Iron is found in various foods, such as lean red meat, tuna, salmon, clams, most beans, leafy greens, tofu and fortified grain products, such as breads and cereals.