7 Best Supplements for Thyroid Health: What the Science Says

Written by Our Editorial Team & Medically Reviewed by Dr. Aisling Lanigan, N.D.

Key Takeaways

• Your thyroid needs specific minerals—especially iodine, selenium, zinc, and iron—to produce and convert thyroid hormones.
• Deficiencies in these key nutrients can contribute to suboptimal thyroid function, even if you don't have a diagnosed thyroid condition.
• Supplementation can help if you're deficient, but more isn't always better. Some nutrients (like iodine and iron) can cause problems in excess.
• If you suspect thyroid issues, get proper testing first. Supplements support thyroid health but don't replace medical treatment when it's needed.
• Always talk to your doctor before starting thyroid-supportive supplements, especially if you're on thyroid medication.

Your thyroid is a small gland with an outsized impact on how you feel every day. When it's working well, you probably don't think about it. When it's not? Fatigue, weight changes, mood shifts, brain fog, temperature sensitivity—the list goes on.

While thyroid issues typically require medical treatment, certain nutrients are essential for your thyroid to function properly. Here's what the science says about supporting thyroid health through nutrition and supplementation.

Why Thyroid Health Matters

Your thyroid is a butterfly-shaped gland at the base of your neck, and it's essentially your body's metabolic control center. It produces hormones—primarily T4 (thyroxine) and T3 (triiodothyronine)—that regulate:

• Metabolism and energy production

• Body temperature

• Heart rate

• Weight management

• Mood and cognitive function

• Menstrual cycles and fertility

• Skin, hair, and nail health

When thyroid hormone levels are off—either too high (hyperthyroidism) or too low (hypothyroidism)—you feel it throughout your entire body.

Burnout symptoms vs. thyroid symptoms →

Thyroid problems are surprisingly common, affecting approximately 7% of the U.S. population. Women are significantly more likely to experience thyroid dysfunction than men, particularly during hormonal transitions like postpartum and perimenopause.

How Your Thyroid Actually Works

To understand which supplements help (and why), it's useful to know the basics of thyroid hormone production:

1. Your pituitary gland releases TSH (thyroid-stimulating hormone), which signals your thyroid to produce hormones

2. Your thyroid produces T4 (the inactive storage form)

3. T4 is converted to T3 (the active form) primarily in your liver and kidneys

4. T3 acts on cells throughout your body to regulate metabolism

Several nutrients are required at each step of this process. Without adequate levels of these nutrients, your thyroid can't do its job efficiently—even if there's no structural problem with the gland itself.

7 Supplements That Support Thyroid Function

Best supplements for women by age →

1. Selenium

What it does: Selenium is essential for converting T4 (inactive) into T3 (active). Your thyroid actually contains more selenium per gram than any other organ in your body. Selenium also protects the thyroid from oxidative damage during hormone production.

What the research shows: Studies confirm that selenium is a necessary cofactor for the deiodinase enzymes that convert T4 to T3. Selenium deficiency can impair this conversion process.

Food sources: Brazil nuts (just 1-2 provide your daily needs), eggs, sardines, tuna, legumes, sunflower seeds

Supplementation notes: The RDA is 55 mcg for adults. Selenium toxicity is possible at high doses (the upper limit is 400 mcg/day), so more is definitely not better. If you're eating a varied diet with occasional Brazil nuts, you may not need a supplement.

2. Zinc

What it does: Zinc is required for thyroid hormone synthesis and helps regulate TSH levels. It's also involved in the conversion of T4 to T3.

What the research shows: A randomized controlled trial found that zinc supplementation positively impacted thyroid hormone levels, particularly T3, and also improved resting metabolic rate in participants.

Food sources: Oysters, beef, crab, pumpkin seeds, chickpeas, cashews, chicken

Supplementation notes: The RDA is 8 mg for women and 11 mg for men. Zinc supplements are generally well-tolerated, but high doses over time can interfere with copper absorption. If supplementing, 15-30 mg daily is typically sufficient.

3. Iron

What it does: Iron is necessary for thyroid peroxidase, the enzyme that produces thyroid hormones. It's also required for efficient T4 to T3 conversion.

What the research shows: Research demonstrates that iron deficiency is associated with impaired thyroid function. This is particularly relevant for menstruating women, who are at higher risk for iron deficiency.

Food sources: Red meat, oysters, dark poultry meat, spinach, lentils, fortified cereals

Supplementation notes: Do not supplement with iron unless you've had your levels tested. Iron overload is harmful and can damage organs. If you're deficient, your doctor will recommend an appropriate dose. Look for gentler forms like iron bisglycinate if supplementation is needed.

4. Iodine

What it does: Iodine is a fundamental building block of thyroid hormones—T3 contains 3 iodine atoms, and T4 contains 4. Without adequate iodine, your thyroid simply cannot produce enough hormones.

What the research shows: Iodine deficiency is one of the most common preventable causes of thyroid dysfunction worldwide. However, research also shows that excessive iodine can also disrupt thyroid function—there's a U-shaped relationship where both too little and too much cause problems.

Food sources: Seaweed (nori, kelp, kombu, wakame), fish, shellfish, iodized salt, dairy, eggs

Supplementation notes: The RDA is 150 mcg for adults (220 mcg during pregnancy, 290 mcg while breastfeeding). Most people get adequate iodine from diet if they use iodized salt. Be cautious with high-dose iodine supplements or excessive seaweed consumption, as too much iodine can worsen thyroid problems.

5. Vitamin D

What it does: Vitamin D receptors are present in thyroid tissue, and vitamin D plays a role in immune regulation—which is relevant because many thyroid conditions (like Hashimoto's) are autoimmune.

What the research shows: Multiple studies have found associations between vitamin D deficiency and thyroid dysfunction, including Hashimoto's thyroiditis and Graves' disease. While more research is needed to establish causation, maintaining adequate vitamin D levels is associated with better thyroid health outcomes.

Food sources: Fatty fish, egg yolks, fortified foods; also synthesized from sun exposure

Supplementation notes: Many people are deficient in vitamin D, especially those in northern climates or who spend limited time outdoors. Testing your levels is ideal. If supplementing, D3 (cholecalciferol) is more effective than D2. Typical maintenance doses range from 1,000-4,000 IU daily, depending on your levels.

Vitamin D and thyroid function →

6. Probiotics

What they do: Your gut and thyroid are connected in several ways. Gut health influences immune function (relevant for autoimmune thyroid conditions), and the gut microbiome may play a role in thyroid hormone metabolism.

What the research shows: This is an emerging area of research. Reviews suggest that the gut microbiome influences thyroid function through several mechanisms, including effects on immune regulation and nutrient absorption (iodine, selenium, zinc, iron). Some preliminary studies suggest probiotic supplementation may support thyroid function, though more research is needed to confirm specific benefits.

Food sources: Yogurt, kefir, sauerkraut, kimchi, miso, kombucha

Supplementation notes: While the direct evidence for probiotics improving thyroid function is still developing, maintaining gut health supports overall nutrient absorption and immune function—both of which matter for thyroid health. Look for multi-strain probiotic formulas with well-researched strains.

7. Ashwagandha

What it does: Ashwagandha is an adaptogen—a class of herbs that help the body adapt to stress. It has been used in Ayurvedic medicine for thousands of years and has gained attention for its potential thyroid-supportive effects.

What the research shows: A randomized, double-blind, placebo-controlled study of 50 participants with subclinical hypothyroidism found that ashwagandha supplementation (600 mg daily for 8 weeks) significantly improved TSH, T3, and T4 levels compared to placebo. This is promising evidence, though it's based on a relatively small study in a specific population (subclinical hypothyroidism). The mechanism may involve ashwagandha's effects on cortisol, as chronic stress can suppress thyroid function.

Supplementation notes: Look for standardized root extract, typically KSM-66® or Sensoril®. Doses in studies have typically been 300-600 mg daily. Important: Ashwagandha may not be appropriate for everyone—those with hyperthyroidism should avoid it, as it may further increase thyroid hormone levels. Consult your healthcare provider before use.

Natural Ways to Support Your Thyroid

Beyond supplementation, lifestyle factors significantly impact thyroid health:

Manage Stress

Chronic stress elevates cortisol, which can interfere with thyroid hormone production and conversion. Stress management isn't optional for thyroid health—it's essential.

Exercise Regularly

Physical activity can stimulate thyroid hormone production and improve your body's sensitivity to thyroid hormones. Both cardiovascular exercise and strength training are beneficial.

Eat Enough (But Not Too Much)

Severe calorie restriction can slow thyroid function as your body downregulates metabolism to conserve energy. On the other hand, maintaining a healthy weight supports thyroid health.

Prioritize Sleep

Poor sleep disrupts hormonal balance across the board, including thyroid function. Aim for 7-9 hours of quality sleep.

Consider Goitrogens (Context Matters)

Goitrogens are compounds that can interfere with iodine uptake in the thyroid. They're found in raw cruciferous vegetables, soy, and some other foods. For most people eating a balanced diet with adequate iodine, these foods are healthy and don't pose a problem. Cooking reduces goitrogen content. Only those with existing iodine deficiency or thyroid conditions eating very large amounts of raw cruciferous vegetables need to be concerned.

Best Foods for Thyroid Health

Selenium-Rich Foods

• Brazil nuts (1-2 daily provides your selenium needs)

• Eggs

• Sardines and tuna

• Sunflower seeds

• Legumes

Iodine-Rich Foods

• Seaweed (nori, kelp, wakame)

• Fish and shellfish

• Iodized salt

• Dairy products

• Eggs

Zinc-Rich Foods

• Oysters

• Beef and poultry

• Pumpkin seeds

• Chickpeas and lentils

• Cashews

Other Thyroid-Supportive Foods

• Leafy greens (for magnesium and other minerals)

• Fatty fish (for omega-3s and vitamin D)

• Berries (antioxidants)

Magnesium for women's hormonal health →

Important Cautions

If You're Taking Thyroid Medication

If you're on thyroid medication (like levothyroxine/Synthroid), be aware that supplements can interact with your medication:

• Take thyroid medication separately from supplements—ideally 4 hours apart, especially from calcium, iron, and magnesium

• Don't start iodine supplements without consulting your doctor, as they can interfere with medication dosing

• Ashwagandha may increase thyroid hormone levels, which could require medication adjustment

Always inform your healthcare provider about any supplements you're taking.

Get Tested First

If you suspect thyroid issues, get proper testing before trying to self-treat with supplements:

• TSH (thyroid-stimulating hormone)

• Free T4

• Free T3

• Thyroid antibodies (if autoimmune thyroiditis is suspected)

Supplements can support thyroid health, but they don't replace proper diagnosis and treatment when there's a real problem.

The Bottom Line

Your thyroid needs specific nutrients—selenium, zinc, iron, iodine, and vitamin D—to produce and convert hormones effectively. When these nutrients are lacking, thyroid function can suffer even without a diagnosable condition.

Strategic supplementation can help fill nutritional gaps, but balance matters. Some thyroid-supportive nutrients (like iodine and iron) can cause problems in excess. Others (like ashwagandha) may not be appropriate for everyone.

The best approach combines nutrient-dense foods, stress management, adequate sleep, regular movement, and targeted supplementation where needed—ideally guided by testing and a healthcare provider who understands your full picture.

Because when your thyroid is happy, you feel the difference everywhere.

The information in this article is for general educational purposes only and is not intended to replace consultation with a qualified healthcare professional. Always consult a doctor or naturopath before starting any supplement, particularly if taking medications or managing a health condition. LunHer products are not intended to diagnose, treat, cure, or prevent any disease.