Does soy impact thyroid function or the absorption of synthroid (medication for hypothyroidism)?
A comprehensive review of the literature published in 2006 concluded that soy does not adversely affect thyroid function. The review further recommended that thyroid function be reassessed if there is a substantial increase or decrease in soy intake, but normal day-to-day variations are unlikely to affect normal thyroid function. Messina M, Redmond G. Effects of soy protein and soybean isoflavones on thyroid function in healthy adults and hypothyroid patients: a review of the relevant literature. Thyroid. 2006 Mar;16(3):249-58.
