Diet for Hypothyroidism: What to Eat, What to Avoid

01What

What is hypothyroidism?

The thyroid is a butterfly-shaped gland in the neck that produces hormones controlling metabolism. In hypothyroidism it makes too little, causing tiredness, weight gain, feeling cold, constipation, dry skin, hair thinning, low mood and slow thinking. The most common cause in developed countries is Hashimoto’s thyroiditis, an autoimmune condition; in some places iodine deficiency is the main cause. Diagnosis is by blood tests (TSH and free T4).

02Medicine

Taking levothyroxine correctly

• Take it with water on an empty stomach, ideally 30–60 minutes before breakfast, or at bedtime at least 3 hours after your last meal, as your doctor advises.
• Be consistent about timing and brand, and have TSH checked 6–8 weeks after dose or brand changes.
• Separate it from calcium, iron, magnesium, aluminium antacids, sucralfate and cholestyramine by about 4 hours.
• Coffee can reduce absorption if taken together; wait at least 30 minutes.
• High-fibre meals, soy products, walnuts and grapefruit juice can interfere if taken at the same time.
• Tell your doctor about new medicines and supplements.
• Do not stop or change dose by yourself.

03Iodine

Iodine: enough, not too much

Iodine is needed to make thyroid hormones. Adults need about 150 µg a day (more in pregnancy and breastfeeding). Good sources are fish and seafood, dairy, eggs and iodised salt. Too little causes hypothyroidism and goitre, but too much (kelp, seaweed supplements, some herbal products) can trigger or worsen thyroid problems, particularly in autoimmune thyroid disease. Avoid high-dose iodine and kelp supplements unless prescribed.

04Selenium

Selenium and other nutrients

• Selenium supports thyroid enzymes; sources include fish, eggs, meat, whole grains and Brazil nuts (1–2 a day is enough). Evidence for supplements in Hashimoto’s is mixed, and excess is toxic.
• Iron: deficiency is common in hypothyroidism and worsens fatigue; test and treat if low, spaced from levothyroxine.
• Vitamin D and B12: deficiencies are more common in autoimmune thyroid disease; check levels.
• Zinc: contributes to hormone function; get it from food (meat, seafood, legumes).
• Fibre and fluids help constipation, a common symptom.
• A varied diet usually provides what you need.

05Myths

Foods people worry about: soy, broccoli and gluten

• Cruciferous vegetables (broccoli, cabbage, kale, cauliflower) contain goitrogens, but normal cooked amounts are fine if iodine intake is adequate.
• Soy can reduce levothyroxine absorption if eaten together; keep soy foods away from your dose by a few hours.
• Gluten: coeliac disease is more common in autoimmune thyroid disease, so get tested if you have digestive symptoms, but gluten-free diets are not needed otherwise.
• Raw foods and “thyroid-boosting” diets lack evidence.
• Goitrogen avoidance is rarely needed.

06Weight

Weight and metabolism

Untreated hypothyroidism slows metabolism modestly and causes fluid retention, usually leading to a gain of a few kilos, not large amounts. Once hormone levels are normal, weight gain is mostly reversible with healthy eating and activity, though some people find it harder. Aim for a balanced diet with plenty of vegetables, lean protein, legumes, whole grains and fibre, regular exercise including strength training, adequate sleep and no crash diets. If you are on a stable dose but gaining significant weight, ask your doctor to check TSH and other causes. See balanced diet for weight loss.

07Plan

A simple eating pattern

• Breakfast: take levothyroxine first with water; 30–60 minutes later, eat oats with fruit and yoghurt.
• Lunch: lentils or fish with vegetables and whole grains.
• Snack: fruit, nuts (a Brazil nut occasionally) or hummus.
• Dinner: eggs or lean meat with roasted vegetables and potatoes.
• Drink water through the day; keep calcium or iron supplements away from the medicine dose.
• Use iodised salt in moderation if you do not eat dairy or seafood, and keep sodium reasonable.

08Tests

Monitoring and biotin

After starting or changing treatment, TSH is checked every 6–8 weeks until stable, then once or twice a year. High-dose biotin (vitamin B7), common in hair and nail supplements, can falsely alter thyroid blood test results, so tell your doctor and stop it a few days before tests if advised. Pregnancy requires closer monitoring and often a dose increase.

10Cases

Three common situations

A person who takes levothyroxine with breakfast coffee and a calcium pill: separate them and take on an empty stomach.

Someone who stopped broccoli to protect the thyroid: it is not necessary in normal amounts.

A woman with Hashimoto’s asking about kelp supplements: avoid; excess iodine can worsen it.

11Summary

Key points to remember

Diet does not replace thyroid hormone, but timing medicine properly, getting enough (not excess) iodine and selenium and eating a balanced diet support health and weight. Avoid kelp and unsupervised supplements. Our nutrition team can help you plan meals around your treatment.

This guide is for general information and does not replace an assessment by your own doctor or dietitian.