What Should I Eat If I Have an Underactive Thyroid?
Quick answer: Support thyroid function with iodine, selenium, and zinc-rich foods. Some foods (cruciferous vegetables, soy) may interfere with thyroid function when eaten in very large quantities, but are generally safe in moderation.
What to Eat
Iodine-rich foods (seafood, fish, seaweed, dairy)
Iodine is essential for producing thyroid hormones T3 and T4 — deficiency is a primary cause of hypothyroidism globally.
Selenium-rich foods (Brazil nuts, tuna, sardines, eggs)
Selenium is required for converting inactive T4 to active T3 — deficiency impairs thyroid hormone activity.
Zinc-rich foods (beef, oysters, pumpkin seeds)
Zinc supports thyroid hormone synthesis and conversion.
Eggs (whole)
Iodine in the yolk + selenium + protein — a complete thyroid-supportive food.
Lean meat and chicken
Zinc and protein — support overall metabolism which is impaired in hypothyroidism.
Berries and antioxidant-rich fruits
Reduce oxidative stress that worsens autoimmune thyroid disease (Hashimoto's, the commonest cause of hypothyroidism).
Nuts and seeds
Selenium, zinc, and anti-inflammatory fats support thyroid and immune function.
What to Avoid
Raw cruciferous vegetables in very large quantities (cabbage, kale, broccoli)
Goitrogens can mildly inhibit iodine uptake by the thyroid when eaten raw in excess — cooking deactivates most goitrogens; normal portions are safe.
Soy-based foods in large amounts
Isoflavones may reduce thyroid hormone absorption — take thyroid medication 4 hours away from soy, and moderate large daily soy consumption.
Gluten (for Hashimoto's patients)
Molecular mimicry between gluten and thyroid antigens exacerbates autoimmune thyroid attack in susceptible individuals.
Highly processed and junk foods
Inflammation worsens autoimmune thyroid disease — a clean, anti-inflammatory diet supports the immune system.
Excess iodine from supplements
Paradoxically, too much iodine can also worsen hypothyroidism in some individuals — don't supplement without a deficiency diagnosis.
Hydration
Stay well hydrated. Green tea in moderation is fine. Avoid fluoridated water if possible (fluoride competes with iodine). Coffee can impair thyroid medication absorption — take medication on an empty stomach, with water only, 30–60 minutes before eating.
Tips
- •Take thyroid medication (levothyroxine) on an empty stomach with water only — coffee, calcium, iron all impair its absorption.
- •Brazil nuts are potent selenium sources — just 2 per day meets the entire daily selenium requirement.
- •If you have Hashimoto's, a trial of gluten-free eating for 12 weeks is worth trying — many patients report symptom improvement.
- •Eating cooked rather than raw cruciferous vegetables is sufficient to minimise goitrogen effects.
- •Vitamin D deficiency is extremely common in Hashimoto's — check and supplement if needed.