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Health benefits of tea have been known for thousands of years. Nowadays, in our search for health elixir, we find ourselves on the same journey as a character from “The Arabian Nights” story who traveled far abroad only to learn that the treasure is back home. Tea seems to be just that treasure. We have been looking far and wide for a miraculous health potion and suddenly a newly emerging body of scientific research spikes our interest in beverage made of leaves of Camellia sinensis plant. Get the leaves withered and steamed- and you have green tea, let them get oxidized – you have black tea, interrupt oxidation halfway – here is your oolong.
Is tea a new power food?
Health benefits of tea have been mentioned since early Chinese scripts dating back to ancient emperor dynasties. As today’s Westerners begin to tune in to healthier eating habits and look for foods packed with nutrients, tea acquired the same status of “power food” as green leafy vegetables, fish, and whole grains.
The tea leaves contain a number of phytochemicals which give the tea its characteristic color, flavor, and healthful qualities. The taste, however, mainly results from various polyphenols, that are recognized to be potentially healthy antioxidants. Other beneficial phytochemicals found in tea are amino acids (theanine), caffeine, fluoride, vitamins, and minerals (1). Let’s take a closer look at some of them.
Antioxidants in tea
Tea polyphenols are natural antioxidants. You may also find terms like tannins, flavonols, flavonoids, theaflavins, and catechins. Don’t get confused! Those are different subtypes of polyphenols found in different kinds of tea.
While catechins are the prevalent polyphenols in green tea, tannins are the main type of polyphenols in black tea. Not only they are potent antioxidants, they are also responsible for black tea’s characteristic color, briskness, and flavor. Black teas are often described as having “tannic quality”, meaning having astringent and bitter notes.
Despite the fact that green tea is getting its popularity as “healthy” tea, all types of tea contain potentially beneficial antioxidants (2). As some nutritionists believe, the tea antioxidants might protect body cells from free radicals and their cell-damaging oxidative effect associated with environmental toxins like cigarette smoke, sunlight, and toxic chemicals (3,4,13).
Amino acids in tea
It is a little-known fact that stimulating effect of tea is different than the energy boost received from coffee. Tea helps to focus and relax simultaneously. It is noted to induce that deeply creative state of mind and sustainable concentration. No wonder Buddhists have been using green tea for centuries during long meditative sessions. The substance responsible for the special effect of tea is the amino acid called L-theanine. L-theanine is found almost exclusively in tea leaves and otherwise is very rare in nature. As studies on animal models show, L-theanine stimulates alpha wave activity in the brain (11,12), inducing relaxation, calming nervous agitation, and therefore counteracting somehow the excessive effect of caffeine (9,16). It is also found to be helpful in following:
– increasing alertness, attention, concentration (14,15)
– lowering blood pressure (7)
– providing a better quality of sleep (16,17)
– mood enhancing, stress relief, preventing and decreasing symptoms of depression (8, 10)
Caffeine content in tea
Caffeine is the world’s most popular, wildly used (and legal!) stimulating substance. It is recognized to be generally safe for adult consumption (mind the lethal dose of 10 grams which is equal to 12 gallons of McDonald’s coffee). Excluding extremes, caffeine is a part of a healthy lifestyle. A morning or afternoon cup of a caffeine-loaded hot beverage is a welcome and often essential boost of energy for many. Caffeine is known to reduce physical fatigue, prevent drowsiness, increase focus, endurance, and task performance. The powerful combination of caffeine and L-theanine in tea really works wonders. It promotes alertness, attention, and overall learning abilities (14,15).
Despite the widespread misconception, caffeine content in tea does not depend on the type (color) of tea (18,19). The level of caffeine in tea varies depending on particular kind of tea and time of preparation (the longer you steep, the more released caffeine in your cup). However, high quality “tippy” teas made of younger tea leaves and buds tend to be higher in caffeine.
In general, caffeine content in tea per serving varies between 14 to 61 mg (19), comparing to 80-175mg per serving in coffee depending on preparation method. Note that herbal teas and rooibos are not made from Camellia Sinensis plant and are naturally caffeine-free.
Vitamins and minerals in tea
And as if that were not enough to appreciate a good cup of tea, here is some more facts about tea nutrients (1) and their potential health benefits.
- Vitamin B1 (Thiamine), Vitamin B2 (Riboflavin) – Support healthy metabolism (21)
- Vitamin C – Antioxidant. It is important for your skin, bones, and connective tissue. (22)
- Carotene (precursor of Vitamin A) – Antioxidant. Helps to maintain healthy teeth, bones, and skin. (23)
- Manganese – It is possibly effective for prevention of osteoporosis. (24)
- Fluoride – natural disinfectant, prevents tooth decay. (25)
What do studies say?
Tea is a wonderful drink for any time of the day. If you are feeling down – drink tea and it will uplift you. If you are hyper and uneasy – it will calm you down. And a good company always sweetens the tea.
The existing body of research on health benefits of tea is quite extensive and constantly growing. Some of those studies show promising results. Consumption of tea found to be associated with 16% lower risk of developing type 2 diabetes (26), 27% lower risk of coronary heart disease (27), 18% lower risk of stroke (27), 26% lower risk of cardiac deaths (27), 34% reduction in risk of ovarian cancer (28), 37% lower risk of Parkinson’s disease (29).
At the end of the day, it doesn’t matter how many double-blind, randomized, and placebo-controlled studies will be conducted with an aim to prove an obvious fact that tea drinkers live longer and healthier lives. We, the casual tea sippers, are well aware that besides all those phytochemicals, vitamins, and mineral, there is a healing and revitalizing power in tea ritual itself. Brewing a real loose leaf tea, slowing down, relaxing and enjoying your cup (three times a day!) – there must be something about it.
-Which way I ought to go from here?
-That depends a good deal on where you want to get to.
Health benefits of tea. Sources.
1. Takehiko Yamamoto, Chemistry and applications of green tea, CRC Press, p. 14, p. 19 1997.
2. Lai Kwok Leung et. al., Theaflavins in Black Tea and Catechins in Green Tea Are Equally Effective Antioxidants, Journal of Nutrition, 2001, Vol. 131, pp.2248-2251.
3. Jeanie Lerche Davis, Antioxidants in Green and Black Tea
4. Benefit of drinking green tea: The proof is in — drinking tea is healthy, says Harvard Women’s Health Watch
5. R.F. Hurrell et. al, Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages., British Journal of Nutrition, April 1999, Vol. 81, No. 4, pp. 289-95
6. Subhuti Dharmananda, Ph.D., Director, Institute for Traditional Medicine, Portland, Oregon, AMINO ACID SUPPLEMENTS IV: THEANINE
7. Yokogoshi H, et al., Reduction effect of theanine on blood pressure and brain 5-hydroxyindoles in spontaneously hypertensive rats, Bioscience, Biotechnology, and Biochemistry 1995; 59: 615-618.
8. Hintikka J, Tolmunen T, Honkalampi K, et al. Daily tea drinking is associated with a low level of depressive symptoms in the Finnish general population. Eur J Epidemiol. 2005;20(4):359-63.
9. Kakuda T, Nozawa A, Unno T, Okamura N, Okai O. Inhibiting effects of theanine on caffeine stimulation evaluated by EEG in the rat. Biosci Biotechnol Biochem. 2000 Feb;64(2):287-93.
10. Hedese S et. al., Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study. Acta Neuropsychiatrica 2016 Jul 11:1-8.
11. Kobayashi K, et al., Effects of l-theanine on the release of alpha-brain waves in human volunteers. Nippon Noegikagako Kaishi 1998; 72 (2): 153-157.
12. Nobre AC, Rao A, Owen GN. L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pac J Clin Nutr. 2008;17 Suppl 1:167-168. (PubMed)
13. Yang Z, Jie G, Dong F, Xu Y, Watanabe N, Tu Y. Radical-scavenging abilities and antioxidant properties of theaflavins and their gallate esters in H2O2-mediated oxidative damage system in the HPF-1 cells. Toxicol In Vitro. 2008;22(5):1250-1256. (PubMed)
14. Camfield DA, Stough C, Farrimond J, Scholey AB. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutr Rev. 2014;72(8):507-522. (PubMed)
15. Bryan J. Psychological effects of dietary components of tea: caffeine and L-theanine. Nutrition Revews. 2008 Feb;66(2):82-90. doi: 10.1111/j.1753-4887.2007.00011.x. (PubMed)
16. Russ Mason, 200 mg of Zen: L-Theanine Boosts Alpha Waves, Promotes Alert Relaxation, Alternative and Complementary Therapies, Vol. 7, No. 2, pp. 91-95, Apr. 2001.
17. I. Hindmarch et. al. A naturalistic investigation of the effects of day-long consumption of tea, coffee and water on alertness, sleep onset and sleep quality, Psychopharmacology, Vol. 149, No. 3, Apr. 2000.
18. M. Friedman et. al., Distribution of catechins, theaflavins, caffeine, and theobromine in 77 teas consumed in the United States, Journal of Food Science, Vol. 70, No. 9, Nov-Dec. 2005, pp. C550-C559.
19. Jenna M. Chin et. al., Technical Note: Caffeine Content of Brewed Teas, Journal of Analytical Toxicology, Vol. 32, No. 8, Oct. 2008 , pp. 702-704(3).
20. CAFFEINE IS NATURAL INSECTICIDE, SCIENTIST SAYS (New York Times)
21. B Vitamins (Medline Plus)
22. Vitamin C (Medline Plus)
23. Vitamin A (Medline Plus)
24. Manganese (Medline Plus)
25. Fluoride (Medline Plus)
26. InterAct Consortium, van Woudenbergh GJ, Kuijsten A, et al. Tea consumption and incidence of type 2 diabetes in Europe: the EPIC-InterAct case-cohort study. PLoS One. 2012;7(5):e36910. (PubMed)
27. Zhang C, Qin YY, Wei X, Yu FF, Zhou YH, He J. Tea consumption and risk of cardiovascular outcomes and total mortality: a systematic review and meta-analysis of prospective observational studies. Eur J Epidemiol. 2015;30(2):103-113. (PubMed)
28. Zhou B, Yang L, Wang L, et al. The association of tea consumption with ovarian cancer risk: A metaanalysis. Am J Obstet Gynecol. 2007;197(6):594 e591-596. (PubMed)
29. Qi H, Li S. Dose-response meta-analysis on coffee, tea and caffeine consumption with risk of Parkinson’s disease. Geriatr Gerontol Int. 2014;14(2):430-439. (PubMed)