Study Confirms: Excessive Green Tea Consumption (1-2L) May Reduce Your Thyroid Function (T3, T4) by Almost 50%
If you drink green tea 24/7 you don't have to wonder if your thyroid is sluggish and your belly growing. |
The authors, Abulfadle K. A., Bakhaat G. A., Shaik R. and Tantry B. A., studied the effect of excessive green tea intake on body weight and serum thyroid hormones in male mice and compared their results to what happens if the rodents are fed only fluoride and caffeine.
Overtraining puts you at a similar risk of low thyroid levels as tons of green tea
- Control (C) group (6 mice) receiving distilled water.
- Green tea (GT) treated group; 6 mice were given a 5 gm% tea hot water extract as their sole water supply (that's similar to you drinking 1-2 L or more).
- Fluoride (FL) treated group, 6 mice were given fluorine excess solution as their only water supply.
- Caffeine (Caf) treated group, 6 mice were treated with caffeine (6.25 mg/kg ip | that's only 0.51 mg/kg body weight for a human and thus not exactly much).
- Propylthiouracil (PTU) treated group, a substance of which we know that it interferes with the synthesis of thyroid hormone, 6 mice were treated with PTU (10 mg/kg ip).
Green tea triggers weight loss only in overweight subjects (Hase. 2001). |
Figure 2: TSH & T3 levels in rodents with green tea (G) or pure catechins (C) in their diets (Chandra. 2010). |
What we do know, at least, is that EGCG interacts with thyroid hormones. Kato et al. (2011), for example, found that it inhibits the effects of thyroid hormones on bone cells. In view of the fact that many studies which have observed ill effects of green tea catechins on the thyroid all used regular extracts which may contain both caffeine and fluoride (Sakamoto. 2001, we cannot tell whether EGCG, EC, ECG & co will have a negative effect on your thyroid health if they come in caffeine- + fluoride-free form. Luckily, Chandra et al (2010) must have foreseen this problem in their 2010 study in which they found that purified green tea catechins (no caffeine, no fluoride | C in Figure 2) have even more pronounced anti-thyroid effects than green tea extracts. The independent anti-thyroid effects of green tea catechins would also exlpain why previous studies show that the effect is sign. less pronounced for black tea extracts (Chandra. 2011) | Comment on FB.
- Abulfadle, Khaled Abdelfattah, et al. "Effect of Excessive Green Tea Versus Fluoride and Caffeine on Body Weight and Serum Thyroid Hormones in Male Mice." Journal of Physiology and Pharmacology Advances 5.2 (2015): 565-573.
- Chandra, Amar K., and Neela De. "Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats." Food and Chemical Toxicology 48.8 (2010): 2304-2311.
- Chandra, Amar K., Neela De, and Shyamosree Roy Choudhury. "Effect of different doses of un-fractionated green and black tea extracts on thyroid physiology." Human & experimental toxicology 30.8 (2011): 884-896.
- Hase, Tadashi, et al. "Anti-obesity Effects of Tea Catechins in Humans [和文]." Journal of oleo science 50.7 (2001): 599-605.
- Kato, Kenji, et al. "(-)-Epigallocatechin gallate inhibits thyroid hormone‑stimulated osteocalcin synthesis in osteoblasts." Molecular medicine reports 4.2 (2011): 297-300.
- Sakamoto, Y., et al. "Goitrogenic effects of green tea extract catechins by dietary administration in rats." Archives of toxicology 75.10 (2001): 591-596.
- Wolfram, Swen, Ying Wang, and Frank Thielecke. "Anti‐obesity effects of green tea: From bedside to bench." Molecular nutrition & food research 50.2 (2006): 176-187.