Are there foods to avoid with hyperthyroidism?

October 24, 2025 •

5 min read

According to the American Thyroid Association, an overactive thyroid, or hyperthyroidism, affects about 1% of the U.S. adult population. While diet alone cannot cure this condition, certain foods can significantly influence thyroid hormone production and may interact with treatments. Learning about the foods to avoid with hyperthyroidism is a crucial part of managing your symptoms effectively alongside medical care.

Quick Summary

An overactive thyroid can be managed with medical treatment and specific dietary adjustments. Limiting high-iodine foods, soy products, and caffeine is generally recommended to help control symptoms and avoid potential interactions with medication.

Key Points

High-Iodine Foods: Strictly limit or avoid high-iodine foods like seaweed, kelp, iodized salt, and most seafood, as they can exacerbate hyperthyroidism.
Caffeine Exacerbates Symptoms: Reduce or eliminate caffeine from your diet to minimize anxiety, tremors, and a rapid heart rate, which are common hyperthyroidism symptoms.
Soy Can Interfere: Limit soy products, such as tofu and soy milk, as they may affect the absorption of thyroid medication and potentially interfere with radioactive iodine treatment.
Cook Goitrogenic Foods: Cruciferous vegetables like broccoli and cabbage contain goitrogens, but cooking them largely deactivates these compounds. Moderate, cooked intake is generally fine for those with hyperthyroidism.
Avoid Processed Foods and Sugars: Limit processed foods, sugary snacks, and fast food to manage blood sugar and avoid hidden iodine, sodium, and unhealthy fats.
Consult Your Doctor: Before making any significant dietary changes, always consult your healthcare provider, especially regarding medication timing and absorption.

The Critical Link Between Diet and Hyperthyroidism

Hyperthyroidism occurs when the thyroid gland produces an excess of thyroid hormones (T3 and T4), accelerating the body's metabolism. This can lead to symptoms like anxiety, rapid heart rate, weight loss, and tremors. The primary cause is often the autoimmune disorder Graves' disease. While medication, radioactive iodine therapy, or surgery are the standard treatments, dietary choices play a supportive role in managing the condition. The foods you eat can influence the thyroid's function, exacerbate symptoms, or interfere with medication absorption, making a strategic diet plan important.

High-Iodine Foods to Strictly Limit

Iodine is the core building block the thyroid gland uses to produce hormones. For someone with hyperthyroidism, an excess of iodine can act like fuel to a fire, causing the thyroid to produce even more hormones and worsening the condition. For those undergoing radioactive iodine treatment, a low-iodine diet (less than 50 micrograms per day) is often prescribed to maximize the treatment's effectiveness. Even otherwise, most people with hyperthyroidism should limit their intake of iodine-rich foods. These include:

Iodized Salt: Swap it for non-iodized salt, such as sea salt or kosher salt.
Seaweed and Kelp: This includes nori (used in sushi), kombu, and other sea vegetables, which contain extremely high levels of iodine.
Seafood: Fish and shellfish like cod, canned tuna, shrimp, and oysters are naturally rich in iodine.
Dairy Products: Milk, cheese, and yogurt are often high in iodine, though levels can vary.
Egg Yolks: The yolks contain significantly more iodine than the whites.
Processed Foods with Carrageenan: This food additive, derived from seaweed, is high in iodine.
Red Dye #3: Certain red food dyes contain iodine and should be avoided.
Iodine Supplements: Unless directed by a doctor, do not take iodine supplements.

The Impact of Caffeine

Caffeine is a stimulant that can dramatically worsen many of the symptoms associated with an overactive thyroid. The increased heart rate, anxiety, and tremors common in hyperthyroidism can be intensified by caffeine intake. For this reason, many health professionals advise limiting or entirely avoiding caffeinated products, including:

Coffee and espresso
Black and green teas (decaf options are better)
Energy drinks
Chocolate
Regular sodas

Beyond just the stimulating effect, coffee can also interfere with the absorption of thyroid medication, making it less effective. A gap of at least 30 to 60 minutes between medication and coffee consumption is generally recommended.

Navigating Soy and its Effects

The relationship between soy and thyroid function is complex and has been a topic of study. While soy foods do not contain significant amounts of iodine, some studies suggest that isoflavones in soy can interfere with thyroid hormone absorption and, in some cases, with radioactive iodine treatment. This potential for interference is why people with hyperthyroidism, especially those undergoing treatment, may be advised to limit soy intake. Common soy products to be mindful of include:

Tofu
Soy milk
Edamame
Soy sauce
Soybean oil

Goitrogens: A Nuanced Approach

Goitrogens are natural compounds found in certain plant-based foods that can interfere with thyroid function by inhibiting iodine uptake. While this can be a concern for people with hypothyroidism, the effect on those with hyperthyroidism is more nuanced. For those with an overactive thyroid, the iodine-blocking effect of goitrogens may be beneficial by potentially suppressing hormone production. However, the effect is only significant when consumed in very large, raw quantities, which is not typical of most diets. Cooking these vegetables also largely deactivates the goitrogenic compounds. Foods containing goitrogens include cruciferous vegetables like:

Broccoli
Cauliflower
Cabbage
Kale
Brussels sprouts
Bok choy

For most people with hyperthyroidism, enjoying these nutrient-dense vegetables in moderation, especially when cooked, is a healthy dietary choice.

Processed Foods and Added Sugars

Many processed foods are high in added sugars, unhealthy fats, and sodium, all of which can be detrimental to overall health and may worsen hyperthyroidism symptoms. High-sugar foods can cause blood sugar spikes, which can intensify palpitations and anxiety. Furthermore, processed foods often contain hidden sources of iodine, especially those made with iodized salt. Avoiding or limiting these items, such as sugary cereals, cakes, and packaged snacks, can support better symptom management.

Hyperthyroidism Diet: What to Avoid vs. What to Embrace


Aspect	Foods to Avoid/Limit	Foods to Embrace (Moderation is Key)
Iodine	Iodized salt, seaweed, shellfish, egg yolks, some dairy	Non-iodized salt, fresh fruit, non-cruciferous vegetables, egg whites
Stimulants	Coffee, energy drinks, black tea, chocolate	Herbal teas, decaf coffee (with care), plenty of water
Soy	Tofu, soy milk, edamame (especially during radioactive iodine treatment)	None needed, but check with a doctor if you rely on soy products.
Goitrogens	Very large, raw quantities of cruciferous vegetables	Cooked cruciferous vegetables (broccoli, cabbage, kale), in moderation
Sugars/Processed	Sugary snacks, processed carbs, fast food	Whole grains (brown rice, quinoa), lean proteins, healthy fats
Nutrients	None needed	Calcium and Vitamin D (low-iodine sources), Selenium, Zinc, Iron

Practical Tips for Managing Your Diet

Prioritize Fresh Foods: Base your diet on whole, unprocessed foods like fresh fruits, vegetables, lean proteins, and whole grains. This reduces your intake of hidden iodine and processed sugars.
Cook Your Vegetables: For those who need to minimize goitrogen intake, cooking cruciferous vegetables can help.
Check Salt and Labels: Use non-iodized salt and read food labels carefully to spot hidden iodine in additives like carrageenan or certain dough conditioners.
Time Your Medication: If taking thyroid medication, follow your doctor's instructions precisely and avoid consuming coffee or other interfering foods within 30–60 minutes of your dose.
Consult a Professional: Work with a healthcare provider or registered dietitian to create a personalized diet plan that meets your nutritional needs while managing your hyperthyroidism.

Conclusion

While a hyperthyroidism diagnosis requires medical treatment, dietary modifications can be a powerful tool for managing symptoms and supporting overall thyroid health. By focusing on a low-iodine diet, limiting stimulants like caffeine, and being mindful of soy intake, you can help reduce the overstimulation of the thyroid gland. For many, the impact of goitrogens is minimal when food is cooked and consumed in moderation, allowing for continued intake of these nutritious vegetables. Remember, the goal is to create a sustainable, balanced diet that works in harmony with your prescribed medical treatment, not to find a quick fix. Always consult your healthcare team before making significant dietary changes, especially if you are on medication or preparing for treatment.

For more information on diet and thyroid conditions, visit the American Thyroid Association.

Frequently Asked Questions

The thyroid gland uses iodine to create thyroid hormones. When you have hyperthyroidism, your thyroid is already overproducing hormones. Consuming too much iodine can worsen this overproduction and make your symptoms more severe.

No, you don't typically need to avoid them entirely. Cruciferous vegetables contain goitrogens, but cooking them reduces their effect. Eating them in moderation, especially when cooked, is generally safe for people with hyperthyroidism.

It is generally advised to limit or avoid coffee and other caffeinated drinks. Caffeine is a stimulant that can intensify hyperthyroidism symptoms like a rapid heartbeat, anxiety, and tremors.

Soy contains compounds called isoflavones that can interfere with the absorption of thyroid medication. For those undergoing radioactive iodine therapy, it may also interfere with treatment effectiveness. Limiting soy intake is often recommended.

No, dietary changes alone cannot cure hyperthyroidism. The condition requires medical treatment, such as medication or radioactive iodine therapy. Diet is a supportive measure to help manage symptoms and support overall health.

You should use non-iodized salt, such as kosher or sea salt, instead of iodized table salt. Many processed foods also contain iodized salt, so reading labels is important.

Reducing your intake of added sugars and processed foods is recommended. Sugar can cause blood sugar spikes that intensify symptoms like heart palpitations and anxiety. A balanced diet low in added sugars is healthier overall.