Hypothyroidism And Green Tea: Does Green Tea Affect The Thyroid?

Since ancient times green tea has been prized for its health-promoting properties. Nowadays, green tea blends are a popular and stylish drink of choice for many health-conscious people, more so than black tea due to the proposed much great health properties it delivers.

Do you drink green tea?

Have you stopped for a moment to think could drinking green tea be harmful? Does green tea affect our thyroid health such as affecting levels of thyroid stimulating hormone(TSH)? We know how important our thyroid gland is so it is important to check the science before going “all in” on something like green tea if we are trying to manage something like weight gain by consumption of green tea in large amounts or by taking concentrated green tea extracts.

Green Tea And Thyroid: Does Green Tea Affect The Thyroid?

An article published in 2010 in the Food and Chemical Toxicology journal was the first to raise serious questions about the possible anti-thyroid effects of green tea.

Research shows at high doses green tea extracts can slow thyroid function. To clarify further, it was reported that green tea has the potential to lower thyroid hormone levels, and reduce activity of the deiodinase enzymes. These enzymes play a crucial role in activating thyroxine (T4) to triiodothyronine (T3). There’s been further studies to show catechins, the main polyphenol compounds found in green tea, can also exert anti-thyroid effects.

Although, it must be said that so far the studies investigating the potentially harmful effects of green tea on thyroid function have been conducted on animals. It will be good to see human studies conducted in the future to either confirm or refute the findings.

This of course brings to light an important issue when investigating published research. Force-feeding laboratory rats with a high amount of green tea extract does not reflect what happens in the real world. No matter what health topic you are researching, human studies are superior to those carried out with animals. The best studies are done using a large cross-section of the general population.

It is important to note that the research on green tea and its effects on the thyroid is still in its early stages. Most of the studies that have been conducted are on animals and not on humans, making it difficult to draw any conclusive findings. Until further research can be conducted on humans, it is important to be aware of the potential risks associated with consuming high amounts of green tea. Additionally, individuals with existing thyroid issues should consult with their doctor before consuming green tea to ensure it is safe for them to do so.

Green Tea and Thyroid Cancer

According to some research, consuming green tea may reduce the chance of thyroid cancer, which has been attributed to its anti-cancer properties.

Almost 3,000 people with thyroid cancer were included in a meta-analysis published in the International Journal of Clinical and Experimental Medicine in 2015. Those who consumed more tea had a lower risk of thyroid cancer, according to the study. There is uncertainty, however, as to whether the anti-cancer benefits are merely due to the compounds in green tea, or if people who drink green tea have a healthier lifestyle as a whole.

More research is needed to determine exactly how green tea may help reduce the risk of thyroid cancer. Some studies have suggested that certain compounds in green tea may act as antioxidants, which could reduce inflammation and prevent oxidative damage. Other studies point to caffeine and catechins, which may help improve the body’s immune system and reduce the risk of cancer. Some researchers think that the polyphenols in green tea may actually target specific cancer cells and inhibit their growth and proliferation.

It is important to note that green tea should not be seen as a cure for thyroid cancer. While it may help reduce the risk, there is still no definitive evidence that it can prevent the disease. It is always best to speak to a healthcare professional about any dietary changes, as everyone’s individual circumstances may vary.

Green Tea and Hypothyroidism

Before you brew up your next cup of green tea you may want to read what I turned up while researching the potential effects of green tea on hypothyroidism. My research even surprised me!

In fact, if you have hypothyroidism I think you may want to avoid drinking this popular health beverage to minimize any potential problems. Let me explain more…

1. Green tea quality varies according to where it’s grown and harvested.

Choosing an organic tea will minimize your exposure to pesticides which are well known thyroid-disrupting chemicals. And as you may already know, organic products should clearly display the organic certification logo on the label so you know it really is organic.

Furthermore, check the country of origin. Green tea is known to accumulate an array of toxins from the soil and water. It’s therefore well worth seeking out a product that is grown, and harvested in an area free of industrial pollution.

2. Green tea may have high levels of fluoride.

Green tea is harvested from shrubs that naturally accumulate fluoride. Fluoride is problematic to the thyroid as it blocks iodine absorption which is required for thyroid hormone production. Research also shows fluoride has adverse effects on bone mineral density.

Even a good quality organically grown tea may have high amounts of fluoride. What’s more, urban water supplies often contain fluoride so if you brew green tea in water that has not been filtered this water is another source of fluoride.

To reduce the amount of fluoride in your green tea, you can use filtered water and buy green tea that has been certified organic. You can also reduce the amount of time you steep the tea. The longer you steep the tea, the more fluoride is released into the drink. It’s also recommended to avoid using tea bags, as most contain tea dust which has higher fluoride levels than the leaf. Lastly, you can add a pinch of baking soda to the tea, which can help to reduce the fluoride levels.

3. Green tea may be too ‘cooling’.

According to Traditional Chinese Medicine (TCM) all foods and drinks have certain qualities that govern how they affect the body. Green tea is considered ‘cooling’ and is therefore indicated to clear heat from the body.

As hypothyroidism is a ‘cold’ condition drinking green tea could further cool the body which is not ideal.

It’s possible to counter the cooling actions of green tea by adding freshly grated ginger to your tea infusion. You probably already know ginger is a wonderful warming remedy that improves circulation.

4. Naturally occurring tannins in green tea reduce iron absorption.

If you have low iron levels, or are prone to low iron stores the general advice is to drink green tea at least two hours away from meals.

You may also want to avoid over-steeping your green tea infusion to limit the tannin level. You see steeping tea releases the tannins which makes the tea taste bitter.

5. Green tea naturally contains caffeine.

Green tea contains a small amount of caffeine which has the potential to disturb sleep quality, especially if consumed at night. For this reason if you are drinking a good quality organic green tea it’s best to drink it sometime in the morning.

In addition, if you ever feel ‘jittery’ after drinking green tea chances are this beverage is too strong for you. Caffeine is known to affect the normal rhythm of the heart. This is the reason individuals with serious heart conditions are advised to avoid any type of tea that contains caffeine. This could also extend to dietary supplements that contain green tea extracts as these are also a source of caffeine.


Q: Does green tea affect the thyroid?

A: Green tea may have an effect on the thyroid.

Q: How does green tea affect thyroid health?

A: The effects of green tea on thyroid health are still being studied.

Q: Can green tea cause weight gain?

A: There is no evidence to suggest that green tea causes weight gain.

Q: Is green tea safe for thyroid patients?

A: Green tea is generally considered safe for thyroid patients.

Q: Are there harmful effects of green tea on the thyroid?

A: There have been some reports of harmful effects of green tea on the thyroid, but more research is needed to confirm these claims.

Q: Does green tea help with thyroid conditions?

A: Green tea may have certain health benefits, but there is no conclusive evidence that it helps with thyroid conditions.

Q: Can I drink green tea if I have an underactive thyroid?

A: It is generally safe for people with hypothyroidism to consume green tea, but it is best to avoid drinking large amounts of it.

Q: Is it safe to consume green tea if I have an autoimmune disease?

A: Green tea is generally safe for people with autoimmune diseases, including thyroid autoimmune conditions.

Q: How many cups of green tea should I drink per day?

A: It is recommended to consume no more than two cups of green tea per day.

Q: Can high consumption of green tea affect the thyroid?

A: Some studies suggest that high green tea consumption may have an impact on the thyroid, but more research is needed to fully understand this relationship.

Associated Key Terms

Here is a reordered and expanded set of descriptions for the key terms related to hypothyroidism and green tea:

Thyroid disorders: Diseases and conditions that affect the thyroid gland, including hypothyroidism, hyperthyroidism, Hashimoto’s thyroiditis, and thyroid cancer.

Thyroid disease: An umbrella term for any condition impacting thyroid health and function. Common thyroid diseases include hypothyroidism, hyperthyroidism, and thyroiditis.

Hypothyroidism: A condition where the thyroid gland does not produce enough thyroid hormones. Symptoms include fatigue, weight gain, hair loss, and sensitivity to cold. It is typically treated with thyroid hormone replacement medication like levothyroxine.

Hyperthyroidism: The opposite of hypothyroidism, this is when the thyroid gland is overactive and produces too much thyroid hormone. Symptoms include rapid heartbeat, anxiety, and unexplained weight loss. 

Hashimoto’s thyroiditis: The most common cause of hypothyroidism in the United States. An autoimmune disorder where the body’s immune system attacks and damages the thyroid gland.

Endocrine: The endocrine system is made up of glands that secrete hormones into the bloodstream to regulate body processes. The thyroid is one of the major endocrine glands.

Thyroid levels: Refers to the measured levels of thyroid hormones T3 and T4 in the blood, which indicate thyroid function. Normal T3 and T4 levels mean euthyroidism or normal thyroid function. 

T3 and T4: The two major thyroid hormones. T4 is the main hormone produced by the thyroid. The body converts T4 into the active hormone T3. 

Low thyroid: Another term for hypothyroidism, when thyroid hormone levels are below the normal range. 

Symptoms of hypothyroidism: Fatigue, weight gain, feeling cold, hair loss, dry skin, constipation, impaired memory, depression, muscle aches.

Treatment for hypothyroidism: Hypothyroidism is treated by replacing the missing thyroid hormones. Levothyroxine is the standard synthetic T4 medication used.

Levothyroxine: The synthetic form of the T4 hormone, this is the most commonly prescribed medication for hypothyroidism. Brand names include Synthroid, Levoxyl, and Tirosint. 

Normal thyroid function: When the thyroid gland produces normal levels of thyroid hormones T3 and T4, allowing proper regulation of metabolism and other body functions. 

Foods rich in iodine: Iodine is crucial for thyroid hormone production. Food sources high in iodine include seafood, dairy products, eggs, prunes, and iodized salt.

Premenopausal thyroid cancer risk: Women under 40 have a higher risk of developing thyroid cancer, especially the papillary and follicular subtypes. Risk starts decreasing after menopause.

Fat oxidation: The breakdown of fat for energy production. Thyroid hormones play an important role in regulating metabolism and fat oxidation.

Health benefits of green tea: Green tea contains antioxidants and nutrients that may help boost metabolism, promote fat loss, and support thyroid health. However, effects may depend on brewing method and quantity consumed. More research is needed.


In conclusion, while green tea is generally considered a healthy and popular beverage, it is important to consider its potential impact on thyroid health, especially for individuals with hypothyroidism. Research suggests that high doses of green tea extracts may slow thyroid function and lower thyroid hormone levels, potentially affecting the conversion of thyroxine (T4) to triiodothyronine (T3). However, most studies on the effects of green tea on thyroid function have been conducted on animals, making it difficult to draw conclusive findings for humans.

It is advisable for individuals with existing thyroid issues, including hypothyroidism, to consult with their healthcare professional before consuming large amounts of green tea or taking green tea extract, to ensure it is safe and suitable for their specific condition. Green tea is known to have anti-cancer properties, and some studies suggest it may reduce the risk of thyroid cancer. However, more research is needed to establish definitive evidence.

Additionally, it is worth noting that green tea naturally contains caffeine, which can affect heart rhythm and may not be suitable for individuals with serious heart conditions. Furthermore, green tea is considered “cooling” in Traditional Chinese Medicine, and for hypothyroidism, which is a “cold” condition, drinking green tea may further cool the body, which is not ideal. Adding ginger to green tea can help counteract its cooling effects.

When it comes to managing hypothyroidism and overall thyroid health, it is important to prioritize a balanced and nutritious diet, along with appropriate medical treatment such as prescribed thyroid medication. While green tea may offer various health benefits, moderation is key. It is always best to speak with a healthcare professional regarding any dietary changes or concerns related to thyroid health.


Ma S, Wang C, Bai J, Wang X, Li C. Association of tea consumption and the risk of thyroid cancer: a meta-analysis. Int J Clin Exp Med. 2015;8(8):14345-51. Link

Bajaj JK, Salwan P, Salwan S. Various Possible Toxicants Involved in Thyroid Dysfunction: A Review. Journal of Clinical and Diagnostic Research : JCDR. 2016;10(1):FE01-FE03. Link

Braun L, Cohen M. Herbs and natural supplements: an evidence-based guide, 3rd ed. Green tea Monograph. Page 572-581. Churchill Livingstone. 2007.

Chandra AK, De N. Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats. Food and chemical Toxicology. 2010;48:2304–11. Link

Chandra AK, De N. Catechin induced modulation in the activities of thyroid hormone synthesizing enzymes leading to hypothyroidism. Mol Cell Biochem. 2013 Feb;374(1-2):37-48. PubMed

Izuora K, Twombly JG, Whitford GM, et al. Skeletal fluorosis from brewed tea. J Clin Endocrinol Metab. 2011 Aug;96(8):2318-24. PubMed

Whyte MP1, Totty WG, Lim VT, Whitford GM. Skeletal fluorosis from instant tea. J Bone Miner Res. 2008 May;23(5):759-69. PubMed

Yu J, Song P, Perry R, Penfold C, Cooper AR. The Effectiveness of Green Tea or Green Tea Extract on Insulin Resistance and Glycemic Control in Type 2 Diabetes Mellitus: A Meta-Analysis. Diabetes Metab J. 2017 Aug;41(4):251-262. PubMed


Additional Questions Answered

Is green tea good for thyroid?

A: Yes, green tea can benefit the thyroid in moderation due to antioxidants that reduce inflammation and autoimmunity implicated in thyroid diseases. Too much green tea daily may inhibit thyroid function.

Green tea for thyroid: Is it OK?

A: Yes, 1-2 cups of green tea daily may benefit the thyroid due to the antioxidants that reduce inflammation associated with thyroid disorders. Too much green tea inhibits thyroid function.

Green tea for hypothyroidism: Is green tea good for hypothyroidism?

A: In moderation, the antioxidants in green tea may help reduce inflammation involved in hypothyroidism and Hashimoto’s disease. Avoid excess daily intake above 2 cups which could inhibit thyroid function.

Is green tea good for hyperthyroidism?

A: The high fluoride content in green tea may help inhibit thyroid function slightly in hyperthyroidism. However, green tea alone is not an adequate treatment and high intake can be harmful.

Green tea thyroid: What are the pros and cons?

A: In moderation green tea antioxidants help reduce inflammation implicated in thyroid disease. But excess intake above 2 cups daily can impair thyroid function and inhibit medication absorption.

Is green tea good for thyroid?

A: Yes, 1-2 cups of green tea daily provides antioxidants that can benefit thyroid health. But high intake of more than 2 cups inhibits the thyroid, whether hypo or hyperthyroidism.

Green tea and thyroid medication: Do I need to watch anything?

A: Yes, green tea may impair intestinal absorption of synthetic thyroid medication like levothyroxine if drinking it too close to dosing. Separate green tea and medication by at least 1-2 hours.

Which green tea is best for thyroid?

A: For thyroid health, choose high quality, pure green teas like matcha, sencha, or gyokuro which have higher antioxidant content and avoid contaminants found in lower grades.

Green tea is good for thyroid right?

A: In moderation 1-2 cups daily, quality green tea can benefit the thyroid due to antioxidants. But excessive intake above 2 cups inhibits thyroid function.

Is green tea bad for thyroid?

A: In high amounts exceeding 2 cups daily, compounds in green tea including fluoride and phytic acid inhibit thyroid function by blocking iodine absorption and thyroid peroxidase.

Green tea: Hypothyroidism casue or not?

A: No, green tea does not cause hypothyroidism in research studies. But excess intake above 2 cups daily may aggravate existing hypothyroidism by suppressing thyroid function.

Is matcha good for thyroid?

A: High quality matcha may benefit the thyroid in moderation (1-2 cups daily) as its antioxidants reduce inflammation. But excess matcha containing fluoride inhibits thyroid function if overconsumed.

Is green tea good for hashimoto’s disease?

A: The antioxidants in 1-2 cups green tea daily may help lower inflammation involved in Hashimoto’s disease. But limit intake to avoid excessive fluoride which can further suppress thyroid function.

Matcha and thyroid: Good match or not?

A: In moderation matcha’s antioxidants benefit the thyroid by reducing inflammation. But excess matcha containing fluoride can impair thyroid function so 1-2 cups maximum per day.

Green tea is good for hypothyroidism, right?

A: Up to 2 cups green tea daily provides antioxidants to lower inflammation associated with hypothyroidism. But excess green tea inhibits the thyroid so moderation is key.

Is green tea good for hypothyroid patients?

A: Yes, 1-2 cups of green tea daily may benefit hypothyroid patients due to anti-inflammatory antioxidants. But excess green tea suppresses thyroid function further so moderation is important.

Is green tea good for thyroid patients?

A: In moderation (1-2 cups daily) green tea antioxidants benefit the thyroid by reducing inflammation. But overconsumption inhibits thyroid function whether hypo or hyperthyroidism.

Can thyroid patients drink green tea?

A: Yes, thyroid patients can drink 1-2 cups green tea daily to lower inflammation naturally. But excessive intake can impair your thyroid function further so moderation is key.

Green tea for hyperthyroidism?

A: The fluoride in green tea may help slightly lower excessive hormone production in hyperthyroidism when 1-2 cups daily. But green tea is not an adequate treatment alone for hyperthyroidism.

Is matcha good for hypothyroidism?

A: The antioxidants in 1-2 daily cups of matcha green tea may help lower inflammation implicated in hypothyroidism. But overconsumption can further inhibit thyroid function.

Is green tea bad for hypothyroidism?

A: Excess green tea containing fluoride can inhibit thyroid function, which could aggravate existing hypothyroidism. Limit to 1-2 cups maximum daily.

Is green tea good for thyroid nodules?

A: Insufficient evidence exists on green tea and thyroid nodules. But its antioxidants may help lower inflammation associated with autoimmune thyroid disease in general when consumed in moderation.

Levothyroxine and green tea: what are the issues?

A: Compounds in green tea can impair intestinal absorption of synthetic thyroid medications like levothyroxine. Separate dosing and tea by at least 1-2 hours.

Does matcha affect thyroid?

A: Yes, matcha can affect the thyroid. The antioxidants may benefit the thyroid gland by reducing inflammation when 1-2 cups daily. But excess matcha inhibits thyroid function.

Is green tea good for your thyroid?

A: In moderation (1-2 cups daily) green tea antioxidants are good for thyroid health by lowering inflammation. But overconsumption inhibits thyroid function so moderation is key.

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