Barry Peatfield, author of Your Thyroid, and How to Keep it Healthy, stresses that the fluoride content of tea
means that you should avoid drinking black, white and green tea
in the morning, and may want to consider giving it up altogether. Fluoride was used in the past as a treatment for hyperthyroid conditions, so effective is it in "slowing" the thyroid and metabolic system.
Calcium, iron, and soy-based formulas will bind with thyroxine and prevent it from being absorbed.