Introduction:
Black tea is made from the leaves of Camelia sinesis, the same plant that green tea leaves originate. In green tea, leaves are mechanically processed, whereas black tea is made by mechanical processing following by oxidation of the leaves which are then dried to stop the oxidation process.
Black tea influence on the mind:.
Black tea, cognitive function, and mood: Drinking black tea was shown to improve the ability to focus attention in two double-blind, randomised, placebo-controlled, crossover studies. In both studies, black tea significantly enhanced accuracy on the switch task and self-reported alertness on the Bond-Lader questionnaire, a mood assessment which grades the degree of mental alertness, calmness and contentedness. There was also better auditory and visual attention after drinking black tea compared to placebo. The two compounds in tea most likely responsible for these effects are theanine, an amino acid found almost exclusively in tea, and caffeine. (1)
Black tea, alertness, visual tasks, fatigue, and headaches:
Results from a randomized, placebo controlled, double-blind, balanced crossover study of the cognitive and mood effects of two compounds both alone [L-theanine (250 mg), caffeine (150 mg)] and in combination (250 mg/150 mg) suggest that beverages, like tea, containing L-theanine and caffeine may have a positive effect on cognition and mood. Twenty four undergraduate students (mean age 21.3 years) took part in the study and were asked to abstain from caffeine and alcohol 12 hours prior to the study. Participants were randomized to a treatment group and received 4 different beverages (250ml drinks as previously described) plus a placebo on separate occasions 7 days apart. On each occasion the tests were carried out before taking the drink, 30 minutes after the drink and 90 minutes post-drink. Each testing session lasted approximately 30 minutes. Compared to the isolated effects of caffeine and L-theanine, the combined action resulted in improvements in visual tasks and mental fatigue ratings. In addition the combination of caffeine and L-theanine also speeded up the completion of a number of cognitive tasks. Participants also reported fewer headache symptoms and felt more alert. Overall, L-theanine with caffeine was found to increasing alertness, reducing tiredness, and reducing headaches. (2)
Black tea and stroke:
Black tea, green tea, and risk of stroke: Black and green tea consumption was associated with a reduced risk of ischemic stroke. Authors analyzed fourteen studies (with a total of 513,804 participants) written from January 1966 to March 2012 to examine the relationship between green and black tea consumption and risk of stroke in a meta-analysis. They found that as tea consumption increased the risk of stroke decreased. Increasing tea consumption by 3 cups a day was associated with a 13% decrease in risk of stroke (RR=0.87). Additionally, results from three studies indicated that as tea drinking increased, this did not necessarily reduce the risk of strokes due to bleeding (cerebral hemorrhage and subarachnoid hemorrhagic strokes). (3)
Oolong, green tea consumption, and risk of stroke:
Oolong and green tea consumption was associated with a reduced risk of ischemic stroke. A case-control study tracked frequency and duration of tea drinking, quantity of dried tea leaves, and types of tea consumed, habitual diet and lifestyle characteristics among 374 ischemic stroke (IS) patients in China from 2007 to 2008; 464 control subjects were also recruited. Researchers found that the risk of ischemic stroke decreased with the increase in the frequency of tea consumption (OR=0.61), duration of tea consumption (OR=0.40) and the increase in the amount of tea leaves brewed (OR-0.27). Additionally, when compared with infrequent or nondrinkers, there was a significant decrease in risk of ischemic associated with drinking at least one cup of tea weekly (P=0.015). Risk reduction was greatest among those drinking one to 2 cups of green or oolong tea daily (a type of Chinese tea). (4)
Tea drinking and cardiovascular disease:
In a population study researchers found that consumption of coffee, green tea and oolong tea and total caffeine intake was linked to a reduced risk of death from cardiovascular disease (CVD). Participants included 76,979 adults followed for 1,010,787 person years, all of whom were ages 40 to 79 and free of stroke, heart disease, and cancer at the start of the study. Compared with non-tea drinkers, women consuming 1-6 cups/week, 1-2 cups/day, 3-5 cups/day and ≥ 6 cups/day had a 66%, 72%, 61%, and 58% reduced rate of coronary heart disease compared to non-tea drinkers. Multivariable hazard ratios were 0.34 (0.06-1.75), 0.28 (0.07-1.11), 0.39 (0.18-0.85) and 0.42 (0.17-0.88) respectively(p = 0.038 for trend). Men drinking ≥ 1 cups/day of oolong tea benefited from a 61% reduced rate of CVD (the HR was 0.39, with range of 0.17-0.88) when compared to non-tea drinkers, (p = 0.049 for trend). Individuals in the second highest quintile of total caffeine intake had a total CVD risk reduction of 38% in men and 22% in women. (5)
Black tea and Parkinson’s disease:
Drinking black tea may reduce the risk of developing Parkinson’s according to a prospective cohort study of 63,257 Chinese participants. According to the results, compared to participants with the lowest black tea intake (lowest 33% of tea drinkers), participants who drank the most black tea (top 33% of tea drinkers) had a 71% reduced risk of Parkinson’s. Caffeine intake (highest intake vs lowest intake) was also associated with a protective effect, reducing Parkinson’s risk by 45%. Additionally, compared to never smokers, current smokers had a 71% reduced risk of Parkinson’s disease. (6)
Summary: Black tea
- The research represented here shows that black tea improved the focus of attention, visual tasks, and mental fatigue. The benefits were believed to come from both caffeine and L-theanine contained in the tea but not in either substance alone.
- Black, green, and oolong tea consumption was associated with a reduced risk of ischemic stroke and cardiovascular disease with the greatest benefit seen when drinking about 1-3 cups per day in the studies mentioned above.
- Please see “green tea” section for research specific to green tea which may have some greater benefits than black tea.
References:
1.De Bruin EA, Rowson MJ, Van Buren L, Rycroft JA, Owen GN. Black tea improves attention and self-reported alertness. Appetite. 2011 Apr;56(2):235-40. http://www.ncbi.nlm.nih.gov/pubmed/21172396
2.Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L-theanine, caffeine and their combination on cognition and mood. Biol Psychol. 2008 Feb;77(2):113-22. Epub 2007 Sep 26. http://www.ncbi.nlm.nih.gov/pubmed?term=18006208
3.Shen L, Song LG, Ma H, Jin CN, Wang JA, Xiang MX. Tea consumption and risk of stroke: a dose-response meta-analysis of prospective studies. J Zhejiang Univ Sci B. 2012 Aug;13(8):652-62. http://www.ncbi.nlm.nih.gov/pubmed/22843186
4.Liang W, Lee AH, Binns CW, Huang R, Hu D, Zhou Q. Tea consumption and ischemic stroke risk: a case-control study in southern China. Stroke. 2009 Jul;40(7):2480-5. Epub 2009 May 28. http://www.ncbi.nlm.nih.gov/pubmed/19478218
5.Mineharu Y, Koizumi A, Wada Y, et al. Coffee, green tea, black tea and oolong tea consumption and risk of mortality from cardiovascular disease in Japanese men and women. J Epidemiol Community Health. 2011 Mar;65(3):230-40. Epub 2009 Dec 8. http://www.ncbi.nlm.nih.gov/pubmed/19996359
6.Tan LC, Koh WP, Yuan JM, et al. Differential effects of black versus green tea on risk of Parkinson’s disease in the Singapore Chinese Health Study. Am J Epidemiol. 2008 Mar 1;167(5):553-60. http://www.ncbi.nlm.nih.gov/pubmed/18156141
