What dietary recommendations are suggested for individuals with hypothyroidism?

Dietary Recommendations for Hypothyroidism

Individuals with hypothyroidism should maintain a consistent daily iodine intake of 150 μg through dietary sources, ensure adequate selenium and iron intake, and avoid excessive iodine consumption that could worsen thyroid dysfunction.

Iodine: The Critical Nutrient

Optimal Iodine Intake

• Adults with hypothyroidism should consume 150 μg of iodine daily through diet, which represents the standard requirement for thyroid hormone synthesis 1.
• Maintaining constant iodine intake through natural food sources has been demonstrated to improve thyroid-stimulating hormone levels and overall thyroid function in hypothyroid patients 2.
• The upper safe limit is 300 μg daily; exceeding this can paradoxically worsen hypothyroidism by inducing autoimmune thyroiditis and elevating TSH levels 1.

Iodine-Rich Food Sources

• Primary dietary sources include seafood, dairy products (milk, yogurt, cheese), and iodized salt 1.
• Dairy and seafood products are the richest natural sources and their regular consumption is essential for adequate iodine status 1.
• Iodized salt provides approximately 60 μg of iodine per gram, making it a reliable but modest contributor when used in recommended amounts 1.

Critical Warning About Excess Iodine

• Excess iodine intake in hypothyroid patients can worsen the condition by increasing TSH levels, lowering thyroid hormone levels, and promoting thyroid autoimmunity 1.
• Avoid non-nutritional iodine sources including iodinated contrast agents, topical iodine disinfectants, amiodarone, and excessive kelp or seaweed supplements 1.

Essential Cofactor Nutrients

Selenium

• Selenium is mandatory for thyroid hormone metabolism as it is required for the function of deiodinase enzymes that convert T4 to active T3 3, 4.
• Selenium deficiency combined with iodine deficiency can lead to severe hypothyroidism (myxedematous cretinism) 3.
• Dietary sources include nuts (especially Brazil nuts), seeds, fish, shellfish, and lean meats 1.
• Important sequencing: In regions with combined iodine and selenium deficiency, iodine must be normalized before selenium supplementation to prevent worsening hypothyroidism 3.

Iron

• Iron deficiency impairs thyroid hormone synthesis by reducing the activity of heme-dependent thyroid peroxidase, the enzyme responsible for thyroid hormone production 3, 4.
• Iron-deficiency anemia blunts the effectiveness of thyroid hormone replacement and iodine supplementation 3.
• Dietary sources include lean meat, liver, seafood, legumes, nuts, and fortified grain products 1.

Vitamin D

• Hypothyroid patients should have vitamin D status monitored, as deficiency can coexist and affect overall metabolic health 1.
• Supplementation should be based on measured 25-hydroxyvitamin D3 levels 1.

Overall Dietary Pattern

Foods to Emphasize

• Consume 3 servings daily of vegetables (excluding excessive amounts of raw cruciferous vegetables which contain goitrogens) 1.
• Include 2-3 servings daily of dairy products, particularly yogurt and cheese, which provide both iodine and protein 1.
• Eat fish and shellfish at least 2 times weekly, prioritizing iodine-rich options like cod, tuna, and shrimp 1.
• Consume whole grains (3 servings daily) to support overall metabolic health 1.
• Include nuts and seeds (4 servings weekly) for selenium content 1.

Foods to Limit or Avoid

• Minimize highly processed foods high in sodium, refined grains, and added sugars, as these can worsen metabolic dysfunction 1.
• Limit processed meats to no more than 1 serving weekly 1.
• Avoid sugar-sweetened beverages entirely 1.
• Restrict sodium intake to less than 2000 mg daily unless using iodized salt as the primary iodine source 1.

Special Dietary Considerations

• Soy isoflavones and certain herbal preparations can interfere with thyroid function; patients should discuss these with their healthcare provider 4.
• Thiocyanates from excessive raw cruciferous vegetables (cabbage, broccoli, cauliflower) can interfere with iodine uptake when consumed in very large amounts 4.
• Vegetarians and vegans are at higher risk for iodine deficiency and should ensure adequate intake through iodized salt, fortified foods, or supplementation 1.

Monitoring and Adjustment

• Patients should maintain consistent dietary iodine intake rather than fluctuating amounts, as constant intake improves thyroid hormone stability 2.
• Those on levothyroxine replacement should take medication consistently, preferably on an empty stomach, and maintain stable dietary patterns 5.
• Pregnant women with hypothyroidism require increased levothyroxine dosing (30% increase) and should ensure iodine intake of 150 μg daily 1.

Common Pitfalls to Avoid

• Do not use iodine supplements without medical supervision, as excessive supplementation can worsen hypothyroidism through autoimmune mechanisms 1.
• Avoid assuming that "more iodine is better"—the therapeutic window is narrow, with both deficiency and excess causing problems 1.
• Do not ignore coexisting iron or selenium deficiency, as these will impair response to thyroid hormone replacement 3, 4.
• Patients should not drastically reduce salt intake without ensuring alternative iodine sources, as this can lead to iodine deficiency 1.