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At Healthfully, we strive to deliver objective content that is accurate and up-to-date. Our team periodically reviews articles in order to ensure content quality. The sources cited below consist of evidence from peer-reviewed journals, prominent medical organizations, academic associations, and government data.
- NIH PubMed: The Combination of L-Theanine and Caffeine Improves Cognitive Performance and Increases Subjective Alertness
- NIH PubMed: The Combination of L-Theanine and Caffeine Improves Cognitive Performance and Increases Subjective Alertness
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Green Tea & the Nervous System
Green tea is the unfermented product of the Camellia sinensis plant. Part of green tea’s appeal is how it makes you feel -- alert, relaxed and energetic. The health benefits green tea have been documented in extensive testing of its antioxidant, cholesterol--lowering, anti--allergen and antihistamine properties. Green tea’s effect on the central nervous system depends on how much you consume and in what form.
Active Ingredients
Green tea is a stimulant. All tea contains caffeine and smaller amounts of theobromine and theophylline. Theobromine is a smooth muscle stimulant. Theophylline, a smooth muscle relaxant, causes restricted air passages to open and is used to treat asthma as it makes breathing easier. Neither is as powerful as caffeine which stimulates the entire central nervous system.
- All tea contains caffeine and smaller amounts of theobromine and theophylline.
Caffeine
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The strongest stimulant in green tea is caffeine, the most widely consumed psychoactive medication in the United States, according to the University of Utah College of Pharmacy 1. Caffeine’s effects on the nervous system include:
- increases in alertness
- focus
- feelings of well--being
- good moods
- quick thinking
- ability to engage longer in an intellectual activity
In extreme cases, over--consumption of caffeine can cause nervous twitching, hallucinations and anxiety.
Potent Relaxant
Green tea contains L-theanine, an amino acid that raises levels of dopamine and serotonin, according to Memorial Sloan--Kettering Cancer Center 2. Theanine is considered a relaxant that calms the brain and the entire nervous system without any reported side affects or drowsiness. When combined with caffeine and other stimulants, as it is in green tea, theanine promotes a feeling of ease and alertness. In tests published in “Nutritional Neuroscience” in December 2010, researchers found that a combination of theanine and caffeine reduced tiredness in test subjects and heightened their accuracy in performing demanding cognitive tasks.
- Green tea contains L-theanine, an amino acid that raises levels of dopamine and serotonin, according to Memorial Sloan--Kettering Cancer Center 2.
- When combined with caffeine and other stimulants, as it is in green tea, theanine promotes a feeling of ease and alertness.
Excess Consumption
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Drinking too much green tea or taking high doses of extracts can overstimulate the nervous system and lead to undesirable effects. Excessive caffeination can cause:
- tremors
- dizziness
- confusion
- insomnia
- restlessness
- agitation
- physical symptoms such as irregular heartbeat
According to the Cam--Cancer Center, it would take amounts of green tea far in excess of normal consumption to produce extreme negative effects. Cam--Cancer recommends that concentrated extracts of green tea be accompanied by educational brochures, detailing proper doses. When consumed in safe doses, and not on an empty stomach, green tea extracts do not result in overstimulation from caffeine.
- Drinking too much green tea or taking high doses of extracts can overstimulate the nervous system and lead to undesirable effects.
- When consumed in safe doses, and not on an empty stomach, green tea extracts do not result in overstimulation from caffeine.
Related Articles
References
- University of Maryland Medical Center: Green Tea
- Memorial Sloan-Kettering Cancer Center: L-Theanine
- NIH PubMed: The Combination of L-Theanine and Caffeine Improves Cognitive Performance and Increases Subjective Alertness
- Cabrera, C., Artacho, R., & Giménez, R. (2006). Beneficial effects of green teaâa review. Journal of the American College of Nutrition, 25(2), 79-99.
- Bogdanski, P., Suliburska, J., Szulinska, M., Stepien, M., Pupek-Musialik, D., & Jablecka, A. (2012). Green tea extract reduces blood pressure, inflammatory biomarkers, and oxidative stress and improves parameters associated with insulin resistance in obese, hypertensive patients. Nutrition Research, 32(6), 421-427.
- WesterterpâPlantenga, M. S., Lejeune, M. P., & Kovacs, E. M. (2005). Body weight loss and weight maintenance in relation to habitual caffeine intake and green tea supplementation. Obesity, 13(7), 1195-1204.
- Jówko, E., Sacharuk, J., BalasiÅska, B., Ostaszewski, P., Charmas, M., & Charmas, R. (2011). Green tea extract supplementation gives protection against exercise-induced oxidative damage in healthy men. Nutrition Research, 31(11), 813-821.
- Kerksick, C. M., Kreider, R. B., & Willoughby, D. S. (2010). Intramuscular adaptations to eccentric exercise and antioxidant supplementation. Amino Acids, 39(1), 219-232.
- Chow, H. S., Hakim, I. A., Vining, D. R., Crowell, J. A., Ranger-Moore, J., Chew, W. M., ... & Alberts, D. S. (2005). Effects of dosing condition on the oral bioavailability of green tea catechins after single-dose administration of Polyphenon E in healthy individuals. Clinical Cancer Research, 11(12), 4627-4633.
- Ullmann, U., Haller, J., Decourt, J. P., Girault, N., Girault, J., Richard-Caudron, A. S., ... & Weber, P. (2003). A single ascending dose study of epigallocatechin gallate in healthy volunteers. Journal of International Medical Research, 31(2), 88-101.
- He, Q., Lv, Y., & Yao, K. (2007). Effects of tea polyphenols on the activities of α-amylase, pepsin, trypsin and lipase. Food Chemistry, 101(3), 1178-1182.
- Warden, B. A., Smith, L. S., Beecher, G. R., Balentine, D. A., & Clevidence, B. A. (2001). Catechins are bioavailable in men and women drinking black tea throughout the day. The Journal of Nutrition, 131(6), 1731-1737.
- Wang, P., Heber, D., & Henning, S. M. (2012). Quercetin increased bioavailability and decreased methylation of green tea polyphenols in vitro and in vivo. Food & Function, 3(6), 635-642.
- Ma, Q., Kim, E. Y., Lindsay, E. A., & Han, O. (2011). Bioactive dietary polyphenols inhibit heme iron absorption in a doseâdependent manner in human intestinal Cacoâ2 cells. Journal of Food Science, 76(5).
- Kim, E. Y., Ham, S. K., Bradke, D., Ma, Q., & Han, O. (2011). Ascorbic acid offsets the inhibitory effect of bioactive dietary polyphenolic compounds on transepithelial iron transport in Caco-2 intestinal cells. The Journal of Nutrition, 141(5), 828-834.
Writer Bio
Benna Crawford has been a journalist and New York-based writer since 1997. Her work has appeared in USA Today, the San Francisco Chronicle, The New York Times, and in professional journals and trade publications. Crawford has a degree in theater, is a certified Prana Yoga instructor, and writes about fitness, performing and decorative arts, culture, sports, business and education .