Key takeaways
- Iodine and L-tyrosine are the two building blocks of thyroid hormones.
- Selenium and zinc help convert T4 into the active hormone T3.
- B12, magnesium and trace minerals support energy and metabolism.
- Both too little and too much iodine can upset thyroid balance.
- Women with thyroid conditions should involve their doctor in supplement choices.
The thyroid is a small, butterfly-shaped gland at the base of your neck, but its influence reaches almost every cell in your body. Its hormones help regulate metabolism, energy, body temperature, heart rate, mood, menstrual cycles and the renewal of hair and skin. Women are several times more likely than men to experience thyroid imbalance, which makes nutrition for this gland especially important.
How the thyroid makes its hormones
The process works in two main steps. First, the thyroid combines iodine with the amino acid tyrosine to make thyroxine (T4). Second, enzymes throughout the body remove one iodine atom from T4 to create triiodothyronine (T3), the active form your cells actually use. Those converting enzymes depend on selenium, and the process also relies on zinc.
The core thyroid nutrients
Iodine
Iodine is the defining ingredient of thyroid hormones; the "4" and "3" in T4 and T3 refer to the number of iodine atoms. Good sources include seaweeds such as kelp and bladderwrack, fish, dairy, eggs and iodized salt. Balance matters: the recommended intake for adults is 150 mcg per day (higher in pregnancy), and very high amounts can also disrupt thyroid function.
L-Tyrosine
This amino acid forms the backbone of every thyroid hormone molecule. The body can make it from phenylalanine, and it is found in protein foods such as poultry, fish, dairy, beans and pumpkin seeds.
Selenium
The thyroid contains more selenium per gram than any other organ. Selenium powers the deiodinase enzymes that convert T4 into T3 and the antioxidant enzymes that protect the gland. Brazil nuts, tuna, sardines, eggs and sunflower seeds are rich sources.
Zinc
Zinc supports hormone production and conversion, and low zinc is linked with thinning hair, which is also a common complaint when the thyroid is under-supported. Find it in oysters, beef, pumpkin seeds, chickpeas and cashews.
Supporting nutrients for energy and metabolism
| Nutrient | Why it matters | Food sources |
|---|---|---|
| Vitamin B12 | Energy production and nerve health; low levels are common alongside thyroid imbalance | Fish, eggs, dairy, fortified foods |
| Magnesium | Involved in hundreds of enzyme reactions, energy and relaxation | Leafy greens, almonds, dark chocolate |
| Copper, manganese, molybdenum | Trace minerals for antioxidant and metabolic enzymes | Nuts, seeds, whole grains, legumes |
| Iron | Needed for the enzyme that makes thyroid hormone | Red meat, lentils, spinach |
Adaptogens and the stress connection
Chronic stress raises cortisol, which can slow the conversion of T4 to T3. Adaptogenic herbs such as ashwagandha and schisandra have traditionally been used to help the body adapt to stress, and small studies on ashwagandha have looked at its effects on thyroid hormone levels.
Sources
- National Institutes of Health, Office of Dietary Supplements – "Iodine: Fact Sheet for Health Professionals."
- National Institutes of Health, Office of Dietary Supplements – "Selenium: Fact Sheet for Health Professionals."
- American Thyroid Association – "Thyroid information for patients."
- Sharma AK, et al. "Efficacy and safety of Ashwagandha root extract in subclinical hypothyroid patients." J Altern Complement Med, 2018.
Common questions
What vitamins are good for the thyroid?
Iodine, selenium, zinc, L-tyrosine, vitamin B12, magnesium and iron all play important roles in thyroid hormone production, conversion and energy metabolism.
Why are women more affected by thyroid imbalance?
Women are several times more likely than men to develop thyroid imbalance, possibly due to hormonal changes during menstrual cycles, pregnancy and menopause, and differences in immune function.
Can you take too much iodine?
Yes. Adults need about 150 mcg per day, and very high intakes can upset thyroid balance, so it is best to stay within recommended amounts and talk to a doctor if you have a thyroid condition.