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Fatigue, feeling unusually cold, weight gain, constipation, dry skin, thinning hair, or a slower heart rate can occur with hypothyroidism (an underactive thyroid). But these symptoms are nonspecific, so nutrition alone should not be used to diagnose or “fix” a thyroid problem. Blood testing—typically TSH and free T4—is needed to determine whether the thyroid is actually underactive.
If hypothyroidism is confirmed, levothyroxine is the standard treatment; nutrients can support normal thyroid physiology and correct deficiencies, but they generally don’t replace thyroid-hormone treatment.
Key nutrients for thyroid function
1. Iodine — essential, but more is NOT better
Iodine is required to manufacture thyroid hormones (T4 and T3). Good food sources include:
- Iodized table salt
- Seafood
- Dairy products
- Eggs
- Some fortified foods
However, iodine is the nutrient where supplementation can backfire. In the U.S., iodine deficiency is relatively uncommon, while excessive iodine—particularly from kelp, seaweed products, iodine drops, or high-dose supplements—can trigger or worsen thyroid dysfunction, especially in people with Hashimoto’s disease.
Practical approach: aim for adequate dietary iodine rather than taking an iodine supplement unless your clinician identifies a reason to do so.
Pregnancy is different: iodine requirements increase, so pregnant or planning-to-be-pregnant people should discuss appropriate iodine intake with their healthcare professional. Current 2026 American Thyroid Association guidance emphasizes the importance of adequate iodine during pregnancy.
2. Selenium — involved in thyroid hormone metabolism
Selenium is incorporated into enzymes involved in antioxidant protection and thyroid-hormone metabolism, including processes involved in converting T4 to the more biologically active T3.
Food sources include:
- Brazil nuts
- Seafood
- Eggs
- Meat and poultry
- Dairy
- Whole grains
- Legumes
There is considerable interest in selenium for Hashimoto’s thyroiditis, and some studies have found reductions in thyroid-antibody levels. However, evidence has not established that routine selenium supplementation improves thyroid hormone requirements or reliably treats hypothyroidism.
Important: don’t assume that more selenium is better. Excess selenium can be harmful. Food-first intake is generally preferable unless a healthcare professional recommends supplementation.
3. Iron — important when deficiency is present
Iron is involved in thyroid hormone synthesis, and iron deficiency can contribute to fatigue independently of thyroid disease.
Consider iron-rich foods such as:
- Lean red meat
- Poultry and seafood
- Lentils and beans
- Tofu
- Spinach and other leafy greens
- Iron-fortified cereals
If you’re experiencing significant fatigue, it can be worthwhile to ask your clinician whether CBC and ferritin/iron studies are appropriate rather than automatically taking iron.
There’s an especially important issue if you take levothyroxine: iron supplements can reduce levothyroxine absorption. They generally need to be separated from thyroid medication; MedlinePlus recommends at least 4 hours between levothyroxine and iron.
4. Zinc — supports thyroid-related enzymes
Zinc participates in numerous enzymes and biological processes involved in thyroid function.
Sources include:
- Oysters and other seafood
- Beef and poultry
- Dairy
- Eggs
- Pumpkin seeds
- Beans and lentils
- Nuts and whole grains
Severe zinc deficiency can impair normal physiology, but there isn’t good evidence that routinely taking high-dose zinc supplements treats ordinary hypothyroidism.
5. Vitamin D — particularly relevant to overall health
Vitamin D isn’t a thyroid hormone and isn’t a direct treatment for hypothyroidism. However, vitamin D deficiency is common, and researchers are studying its relationship with autoimmune thyroid diseases such as Hashimoto’s. NIDDK notes vitamin D and selenium as areas of ongoing research rather than established treatments.
Food sources include:
- Fatty fish
- Egg yolks
- Fortified milk or plant milks
- Fortified cereals
A blood 25-hydroxyvitamin D test can determine whether supplementation is actually needed.
6. Vitamin B12 — worth considering when fatigue is prominent
B12 isn’t specifically a “thyroid booster,” but B12 deficiency can cause fatigue, weakness, neurological symptoms, and anemia. Autoimmune thyroid disease can occur alongside other autoimmune conditions, including pernicious anemia, which causes B12 deficiency.
Sources include:
- Fish and seafood
- Meat
- Eggs
- Dairy
- Fortified nutritional yeast or cereals
People following a vegan diet have a particularly important reason to ensure adequate B12 intake.
7. Magnesium — supports general metabolic function
Magnesium participates in hundreds of biochemical reactions, including energy metabolism and muscle and nerve function. It isn’t a treatment for hypothyroidism, but inadequate intake can contribute to problems such as fatigue or muscle symptoms.
Good sources include:
- Pumpkin seeds
- Almonds and other nuts
- Beans
- Whole grains
- Dark leafy vegetables
- Avocado
Again, correcting an actual deficiency is different from taking large doses in an attempt to stimulate the thyroid.
What about calcium?
Calcium is essential for bone health, but calcium supplements can interfere with levothyroxine absorption.
If you take thyroid medication, calcium-containing supplements or antacids should generally be separated from levothyroxine by at least 4 hours.
This doesn’t mean you should avoid calcium-rich foods. It mainly means that supplement timing matters.
Foods you don’t necessarily need to eliminate
A common misconception is that someone with hypothyroidism must completely avoid:
- Broccoli
- Cauliflower
- Cabbage
- Brussels sprouts
- Kale
- Soy
For most people, normal amounts of these foods as part of a balanced diet aren’t something that needs to be eliminated. The bigger concern is excessive iodine supplementation, particularly in people with autoimmune thyroid disease.
Soy and high-fiber diets can affect levothyroxine absorption in some circumstances, so consistency and medication timing are more useful than unnecessarily banning nutritious foods.
The most important issue: levothyroxine timing
If you’re already taking levothyroxine, nutrition becomes partly a medication-absorption issue.
A commonly recommended approach is to take levothyroxine on an empty stomach and consistently separate it from interfering substances. Iron and calcium supplements are particularly important, generally requiring a 4-hour separation. Coffee/espresso, soy, grapefruit juice, and some multivitamins can also affect absorption.
Don’t change your thyroid medication dose based on symptoms alone. Too much thyroid hormone can cause problems including palpitations, atrial fibrillation, and bone loss.
A practical thyroid-supportive eating pattern
Rather than looking for a single “thyroid superfood,” aim for a varied diet containing:
- Protein: fish, eggs, poultry, lean meat, beans, lentils, tofu
- Iodine-containing foods: seafood, dairy, eggs, appropriately used iodized salt
- Selenium-containing foods: seafood, eggs, meat, legumes, nuts
- Iron-containing foods: meat, seafood, beans, lentils, leafy greens
- Zinc-containing foods: seafood, meat, dairy, seeds and legumes
- B12-containing foods: fish, meat, eggs, dairy or fortified foods
- Vitamin-D sources: fatty fish and fortified foods
- Magnesium-rich plant foods: nuts, seeds, legumes, whole grains and leafy greens
- Plenty of vegetables and fruit
- Adequate fiber and fluids
This approach supports overall metabolic health without relying on high-dose supplements.
If you’re experiencing fatigue, cold intolerance, and weight gain
Don’t assume you simply need iodine or a “thyroid supplement.” Those symptoms can arise from hypothyroidism, anemia/iron deficiency, B12 deficiency, inadequate sleep, depression, medication effects, and other conditions. NIDDK specifically notes that fatigue and weight gain don’t necessarily mean someone has hypothyroidism.
A clinician can determine whether testing such as TSH, free T4, CBC, ferritin/iron studies, B12, or vitamin D makes sense based on your circumstances.
Bottom line: the thyroid needs iodine, selenium, iron, zinc and several vitamins for normal physiology, but deficiency correction—not megadosing—is the goal. There is no proven collection of supplements that naturally replaces thyroid hormone when the thyroid is genuinely underactive, and professional guidelines caution against using dietary supplements as a treatment for hypothyroidism.
If you’d like, I can also give you a 7-day hypothyroidism-friendly meal plan with breakfast, lunch, dinner, snacks, and the best timing around levothyroxine.