Soy and Thyroid Health
Soy (soya) is a legume and common dietary protein source that has clinically relevant interactions with thyroid treatment.
Interactions with Thyroid Treatment
Radioactive Iodine Treatment
Animal studies show soy ingestion interferes with radioactive iodine uptake. Patients preparing for radioactive-iodine-treatment are advised to avoid soy products in the lead-up to the procedure (alongside following a low-iodine-diet).
Levothyroxine Absorption
Soy interferes with levothyroxine absorption. Patients taking levothyroxine should:
- Ideally avoid soy altogether, or
- Leave at least four hours between eating soy and taking levothyroxine.
Common Soy-Containing Foods
- Soy milk
- Soy sauce
- Tofu
- Edamame beans
- Soybean oil
- Soy protein powder
Hyperthyroidism and Autoimmune Disease
Soy’s interaction with hyperthyroidism is primarily a treatment-interference issue rather than a direct worsening of the underlying condition.