Table of ContentsView AllTable of ContentsEffect on MetabolismHealth ImpactSide EffectsForms and Usage
Table of ContentsView All
View All
Table of Contents
Effect on Metabolism
Health Impact
Side Effects
Forms and Usage
In terms of safety, how you consume green tea matters. Research suggests it is safe to drink green tea in moderation if you have thyroid disease. Drinking large amounts of green tea or using green tea extracts, however, should be avoided because it may interact with thyroid medication and negatively affect T3, T4, and TSH levels.
This article discusses green tea, your thyroid, and weight loss. It also reviews what you need to know about enjoying green tea safely if you have thyroid disease.
Mariya Bibikova / E+ / Getty Images
Green Tea’s Effect on Metabolism
Research shows that green tea extract boosts your metabolic rate while also promoting fat burning.While scientists initially attributed this to its caffeine, additional studies found bioactive ingredients in green tea mayincrease metabolismand fat oxidation.
Catechins, a type of flavonoid found in green tea, can help to break down excess body fat. Caffeine and catechins appear to work synergistically to increase the amount of energy the body uses.
While all this sounds encouraging, it is important to keep things in perspective. Even in the studies that found weight loss among those drinking green tea, the degree of weight loss was quite small.
In fact, if you put sugar in your green tea, the added calories will cancel out the extra calories the tea may help you burn.
How Much Caffeine Is Really in Your Green Tea?
The Relationship Between Thyroid Hormones, Metabolism, and Weight
Green Tea and Thyroid Health
Research is unclear on the impact of green tea on thyroid health. In animal studies, green tea has been linked to both improvements and worsening of thyroid conditions.
Some studies found green tea may suppress thyroid function and increase the risk of goiters.Other studies found green tea extract may promote thyroid healing.However, both of these studies were performed on rats, and it is unclear how this may translate to humans.
In vitro (lab) studies also suggest compounds in green tea may be beneficial for Hashimoto’s thyroiditis, an autoimmune disease.
Green tea extract was found to activate thyroid peroxidase in the laboratory. According to researchers, these findings suggest green tea may promote thyroid health for people with underactive thyroids.
While these studies are promising, clinical trials are needed to show how green tea may impact thyroid health in humans.
Can Green Tea Prevent Thyroid Cancer?Some research suggests that green tea may cut the risk of thyroid cancer.However, it is unclear whether compounds in the tea are solely responsible for this or if the anti-cancer benefits are due to the fact that people who drink green tea may be more likely to adopt a healthier lifestyle in general.
Can Green Tea Prevent Thyroid Cancer?
Some research suggests that green tea may cut the risk of thyroid cancer.However, it is unclear whether compounds in the tea are solely responsible for this or if the anti-cancer benefits are due to the fact that people who drink green tea may be more likely to adopt a healthier lifestyle in general.
Side Effects and Interactions
A cup or two of green tea a day is generally thought to be safe for thyroid patients.In this respect, it is different from some of the prescription drugs for obesity, as well as herbal products likeephedra, which can raise heart rates and blood pressure and are not recommended for those withthyroid disease.
Green tea may, however, interfere with the thyroid medication levothyroxine. Research shows caffeine in different types of tea can inhibit the absorption of the medication.
If you take levothyroxine or other thyroid medications, it is a good idea to lower your caffeine intake in general. You should also leave at least 30 minutes between taking the medicine and drinking tea, coffee, or other caffeinated products.
In contrast, there have been some studies that suggest green tea extracts—which greatly concentrate the catechins found in the tea—are not as safe if you have thyroid disease. Among the concerns:
Given this, it may not be safe for people with thyroid disease to take green tea extract.
Guide to Dietary Supplements and Thyroid Disease
Incorporating Green Tea into Your Day
There are no official guidelines on how to incorporate green tea into your diet. It’s available in several forms, such as tea bags, loose tea, supplements, extracts, and in iced tea products. Except for supplements and extracts, which may be toxic if overused, any of these forms of green tea would be fine.
While green tea contains significantly less caffeine than coffee, it still supplies 30 to 40 milligrams (mg) per cup, which can inhibit proper thyroid medication absorption.This is why there should be a 30 minute gap between when you take your medication and when you take your first sip of tea.
A Word From Verywell
While green tea may have some metabolism-boosting effects, it is only meant to be taken in conjunction with standard weight-loss programs, and will not help you lose significant amounts of weight on its own.
How Herbs Can Affect Thyroid Disease
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Rothenberg DO, Zhou C, Zhang L.A review on the weight-loss effects of oxidized tea polyphenols.Molecules. 2018;23(5):1176. doi:10.3390/molecules23051176Lai YW, Huang SM.Tea consumption affects the absorption of levothyroxine.Front Endocrinol(Lausanne). 2022;13:943775. doi:10.3389/fendo.2022.943775Jurgens T, Whelan AM.Can green tea preparations help with weight loss?Can Pharm J(Ott). 2014;147(3):159–60. doi:10.1177/1715163514528668Chandra AK, De N.Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats.Food Chem Toxicol. 2010;48(8-9):2304-11. doi:10.1016/j.fct.2010.05.064Zaki SM, Hussein GHA, Helal GM, Arsanyos SF, Abd Algaleel WA.Green tea extract modulates lithium-induced thyroid follicular cell damage in rats.Folia Morphol (Warsz). 2022;81(3):594-605. doi:10.5603/FM.a2021.0052Habza-Kowalska E, Gawlik-Dziki U, Dziki D.Mechanism of action and interactions between thyroid peroxidase and lipoxygenase inhibitors derived from plant sources.Biomolecules. 2019;9(11):663. doi:10.3390/biom9110663Ma 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.National Center for Complementary and Integrative Health.Green tea.Bajaj JK, Salwan P, Salwan S.Various possible toxicants involved in thyroid dysfunction: a review.J Clin Diagn Res. 2016;10(1):FE01-3. doi:10.7860/JCDR/2016/15195.7092Grajecki D, Ogica A, Boenisch O, Hübener P, Kluge S.Green tea extract-associated acute liver injury: Case report and review.Clin Liver Dis(Hoboken). 2022;20(6):181–7. doi:10.1002/cld.1254Jówko E. Chapter 8:Green Tea Catechins and Sport Performance. In: Lamprecht M, ed.Antioxidants in Sport Nutrition. Boca Raton (FL): CRC Press/Taylor & Francis; 2015.Additional ReadingVenables, M, Hulston, C, et al. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans.The American Journal of Clinical Nutrition, Volume 87, Issue 3, 1 March 2008, Pages 778–784. doi: 10.1093/ajcn/87.3.778Westerterp-Plantenga, MS.Green tea catechins, caffeine and body-weight regulation.Physiol Behav.2010 Apr 26;100(1):42-6. doi:10.1016/j.physbeh.2010.02.005. Epub 2010 Feb 13.
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Rothenberg DO, Zhou C, Zhang L.A review on the weight-loss effects of oxidized tea polyphenols.Molecules. 2018;23(5):1176. doi:10.3390/molecules23051176Lai YW, Huang SM.Tea consumption affects the absorption of levothyroxine.Front Endocrinol(Lausanne). 2022;13:943775. doi:10.3389/fendo.2022.943775Jurgens T, Whelan AM.Can green tea preparations help with weight loss?Can Pharm J(Ott). 2014;147(3):159–60. doi:10.1177/1715163514528668Chandra AK, De N.Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats.Food Chem Toxicol. 2010;48(8-9):2304-11. doi:10.1016/j.fct.2010.05.064Zaki SM, Hussein GHA, Helal GM, Arsanyos SF, Abd Algaleel WA.Green tea extract modulates lithium-induced thyroid follicular cell damage in rats.Folia Morphol (Warsz). 2022;81(3):594-605. doi:10.5603/FM.a2021.0052Habza-Kowalska E, Gawlik-Dziki U, Dziki D.Mechanism of action and interactions between thyroid peroxidase and lipoxygenase inhibitors derived from plant sources.Biomolecules. 2019;9(11):663. doi:10.3390/biom9110663Ma 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.National Center for Complementary and Integrative Health.Green tea.Bajaj JK, Salwan P, Salwan S.Various possible toxicants involved in thyroid dysfunction: a review.J Clin Diagn Res. 2016;10(1):FE01-3. doi:10.7860/JCDR/2016/15195.7092Grajecki D, Ogica A, Boenisch O, Hübener P, Kluge S.Green tea extract-associated acute liver injury: Case report and review.Clin Liver Dis(Hoboken). 2022;20(6):181–7. doi:10.1002/cld.1254Jówko E. Chapter 8:Green Tea Catechins and Sport Performance. In: Lamprecht M, ed.Antioxidants in Sport Nutrition. Boca Raton (FL): CRC Press/Taylor & Francis; 2015.Additional ReadingVenables, M, Hulston, C, et al. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans.The American Journal of Clinical Nutrition, Volume 87, Issue 3, 1 March 2008, Pages 778–784. doi: 10.1093/ajcn/87.3.778Westerterp-Plantenga, MS.Green tea catechins, caffeine and body-weight regulation.Physiol Behav.2010 Apr 26;100(1):42-6. doi:10.1016/j.physbeh.2010.02.005. Epub 2010 Feb 13.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Rothenberg DO, Zhou C, Zhang L.A review on the weight-loss effects of oxidized tea polyphenols.Molecules. 2018;23(5):1176. doi:10.3390/molecules23051176Lai YW, Huang SM.Tea consumption affects the absorption of levothyroxine.Front Endocrinol(Lausanne). 2022;13:943775. doi:10.3389/fendo.2022.943775Jurgens T, Whelan AM.Can green tea preparations help with weight loss?Can Pharm J(Ott). 2014;147(3):159–60. doi:10.1177/1715163514528668Chandra AK, De N.Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats.Food Chem Toxicol. 2010;48(8-9):2304-11. doi:10.1016/j.fct.2010.05.064Zaki SM, Hussein GHA, Helal GM, Arsanyos SF, Abd Algaleel WA.Green tea extract modulates lithium-induced thyroid follicular cell damage in rats.Folia Morphol (Warsz). 2022;81(3):594-605. doi:10.5603/FM.a2021.0052Habza-Kowalska E, Gawlik-Dziki U, Dziki D.Mechanism of action and interactions between thyroid peroxidase and lipoxygenase inhibitors derived from plant sources.Biomolecules. 2019;9(11):663. doi:10.3390/biom9110663Ma 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.National Center for Complementary and Integrative Health.Green tea.Bajaj JK, Salwan P, Salwan S.Various possible toxicants involved in thyroid dysfunction: a review.J Clin Diagn Res. 2016;10(1):FE01-3. doi:10.7860/JCDR/2016/15195.7092Grajecki D, Ogica A, Boenisch O, Hübener P, Kluge S.Green tea extract-associated acute liver injury: Case report and review.Clin Liver Dis(Hoboken). 2022;20(6):181–7. doi:10.1002/cld.1254Jówko E. Chapter 8:Green Tea Catechins and Sport Performance. In: Lamprecht M, ed.Antioxidants in Sport Nutrition. Boca Raton (FL): CRC Press/Taylor & Francis; 2015.
Rothenberg DO, Zhou C, Zhang L.A review on the weight-loss effects of oxidized tea polyphenols.Molecules. 2018;23(5):1176. doi:10.3390/molecules23051176
Lai YW, Huang SM.Tea consumption affects the absorption of levothyroxine.Front Endocrinol(Lausanne). 2022;13:943775. doi:10.3389/fendo.2022.943775
Jurgens T, Whelan AM.Can green tea preparations help with weight loss?Can Pharm J(Ott). 2014;147(3):159–60. doi:10.1177/1715163514528668
Chandra AK, De N.Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats.Food Chem Toxicol. 2010;48(8-9):2304-11. doi:10.1016/j.fct.2010.05.064
Zaki SM, Hussein GHA, Helal GM, Arsanyos SF, Abd Algaleel WA.Green tea extract modulates lithium-induced thyroid follicular cell damage in rats.Folia Morphol (Warsz). 2022;81(3):594-605. doi:10.5603/FM.a2021.0052
Habza-Kowalska E, Gawlik-Dziki U, Dziki D.Mechanism of action and interactions between thyroid peroxidase and lipoxygenase inhibitors derived from plant sources.Biomolecules. 2019;9(11):663. doi:10.3390/biom9110663
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.
National Center for Complementary and Integrative Health.Green tea.
Bajaj JK, Salwan P, Salwan S.Various possible toxicants involved in thyroid dysfunction: a review.J Clin Diagn Res. 2016;10(1):FE01-3. doi:10.7860/JCDR/2016/15195.7092
Grajecki D, Ogica A, Boenisch O, Hübener P, Kluge S.Green tea extract-associated acute liver injury: Case report and review.Clin Liver Dis(Hoboken). 2022;20(6):181–7. doi:10.1002/cld.1254
Jówko E. Chapter 8:Green Tea Catechins and Sport Performance. In: Lamprecht M, ed.Antioxidants in Sport Nutrition. Boca Raton (FL): CRC Press/Taylor & Francis; 2015.
Venables, M, Hulston, C, et al. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans.The American Journal of Clinical Nutrition, Volume 87, Issue 3, 1 March 2008, Pages 778–784. doi: 10.1093/ajcn/87.3.778Westerterp-Plantenga, MS.Green tea catechins, caffeine and body-weight regulation.Physiol Behav.2010 Apr 26;100(1):42-6. doi:10.1016/j.physbeh.2010.02.005. Epub 2010 Feb 13.
Venables, M, Hulston, C, et al. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans.The American Journal of Clinical Nutrition, Volume 87, Issue 3, 1 March 2008, Pages 778–784. doi: 10.1093/ajcn/87.3.778
Westerterp-Plantenga, MS.Green tea catechins, caffeine and body-weight regulation.Physiol Behav.2010 Apr 26;100(1):42-6. doi:10.1016/j.physbeh.2010.02.005. Epub 2010 Feb 13.
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