What foods should be avoided in hypothyroidism (underactive thyroid)?

Foods to Avoid in Hypothyroidism

Patients with hypothyroidism should avoid soy products, especially when taking levothyroxine, as they can significantly interfere with thyroid hormone absorption and may require increased medication dosages to maintain euthyroid status. 1, 2

Foods That Interfere with Thyroid Medication Absorption

• Soy products (soy milk, tofu, soy formula, etc.) should be avoided within 4 hours of taking levothyroxine as they can inhibit absorption and lead to continued hypothyroidism despite appropriate medication dosing 2
• High-fiber foods should be separated from levothyroxine administration by at least 4 hours as they can bind to the medication and reduce its absorption 3
• Coffee/espresso can interfere with levothyroxine absorption and should not be consumed within 1 hour of taking thyroid medication 3
• Calcium-rich foods (dairy products, calcium-fortified juices) should be consumed at least 4 hours apart from levothyroxine administration 1
• Iron supplements should be taken at least 4 hours apart from levothyroxine as they can significantly reduce medication absorption 1

Iodine Considerations

• Excessive iodine intake should be avoided as it can worsen hypothyroidism in iodine-sufficient individuals 4
• Iodine-containing medications (amiodarone, iodinated contrast agents, topical iodine disinfectants) should be used with caution in hypothyroid patients 4
• Ensure adequate but not excessive iodine intake - adults need approximately 150 μg/day, with an upper limit of 300 μg/day 4

General Dietary Recommendations for Hypothyroidism

• Limit processed foods high in sodium, as hypothyroid patients may have increased cardiovascular risk 4, 5
• Focus on whole foods including fruits, vegetables, whole grains, lean proteins, and healthy fats 4
• Include iodine-rich foods in moderation such as fish, dairy products, and iodized salt 4
• Consider milk and dairy products as they are important sources of iodine in many diets (38% of iodine intake in non-pregnant adults) 4
• Be aware that organic milk and plant-based milk alternatives typically contain less iodine than conventional milk 4

Special Considerations

• Cruciferous vegetables (broccoli, kale, cabbage) have traditionally been thought to interfere with thyroid function, but current evidence suggests they are safe to consume in reasonable amounts for most hypothyroid patients who are iodine-sufficient 6
• Gluten avoidance may be beneficial only in patients with celiac disease or gluten sensitivity, as these conditions can affect levothyroxine absorption 3, 6
• Patients with diabetes and hypothyroidism should monitor blood glucose carefully as thyroid hormone replacement can affect glycemic control 1

Medication Administration Guidelines

• Take levothyroxine as a single daily dose on an empty stomach, 30-60 minutes before breakfast with a full glass of water 1
• Maintain consistent timing of medication and food intake to ensure stable absorption 1
• Do not administer levothyroxine with foods known to decrease absorption, particularly soy-based products 1

Following these dietary guidelines can help optimize thyroid function and medication effectiveness in patients with hypothyroidism, potentially improving symptoms and quality of life.