Dairy foods
If you are taking medications for hypothyroidism, avoid eating calcium-rich foods – such as milk, cheese and yogurt – at the same time as your levothyroxine tablet. Calcium interferes with the absorption of levothyroxine and the British Thyroid Foundation recommends a four-hour interval between levothyroxine intake and consumption of foods or supplements containing calcium (iv). Iron supplements can also prevent your body from absorbing levothyroxine, so leave a gap of two hours between the two (remember, some vitamin and mineral supplements also contain iron) (iv).
Soya-based foods
Like calcium-containing foods, soy-based foods such as tofu, soy milk and soy also affect the absorption of levothyroxine. Therefore, allow as much time as possible between taking your levothyroxine and eating foods containing soy (the British Thyroid Foundation recommends completely avoiding soy) (iv).
Cruciferous vegetables
Members of the Brassica family of plants – including cabbage, cauliflower, broccoli, kale and Brussels cabbage – contain substances called goitrogens that affect the thyroid gland and its ability to release thyroid hormones. This explains why people with thyroid disease are often recommended to avoid such foods. However, experts believe that you should eat a lot of them before they cause real problems (v).