Black tea – helpful or harmful? A review of the evidence

Abstract

Objective: To consider whether consumption of black tea has a positive or negative impact on health. Design: Databases were searched for relevant epidemiological and clinical studies published between 1990 and 2004. Results: Clear evidence was found for coronary heart disease (CHD), where an intake of X3 cups per day related to risk reduction. The mechanism could involve the antioxidant action of tea polyphenols. While experimental models have suggested that flavonoids attenuated cancer risk, epidemiological studies failed to demonstrate a clear effect for tea, although there is moderate evidence for a slightly positive or no effect of black tea consumption on colorectal cancer. Studies on cancer were limited by sample sizes and insufficient control of confounders. There is moderate evidence suggestive of a positive effect of black tea consumption on bone mineral density although studies were few. There is little evidence to support the effect of tea on dental plaque inhibition but evidence to support the contribution of tea to fluoride intakes and thus theoretical protection against caries. There was no credible evidence that black tea (in amounts typically consumed) was harmful. Normal hydration was consistent with tea consumption when the caffeine content was o250 mg per cup. A moderate caffeine intake from tea appeared to improve mental performance, although sample sizes were small. There was no evidence that iron status could be harmed by tea drinking unless populations were already at risk from anaemia. Conclusions: There was sufficient evidence to show risk reduction for CHD at intakes of X3 cups per day and for improved antioxidant status at intakes of one to six cups per day. A maximum intake of eight cups per day would minimise any risk relating to excess caffeine consumption. Black tea generally had a positive effect on health. Sponsorship: The Tea Council. The authors confirm that the sponsors played no role in the writing of this review.

Distribution patterns of polyphenols and alkaloids in instant coffee, soft and energy drinks, and tea

“…Another relevant flavan-3-ol present in both kinds of samples was EGCG, which showed a much lower concentration in fermented tea. These large concentration differences were expected since flavan-3-ols are oxidised or condensed to other large polyphenolic molecules such as theaflavins and thearubins during the fermentation process (Gardner et al 2007). …”

“…Intake of tea has been suggested to be associated with a decreased risk of cardiovascular diseases and cancer (Gardner et al 2007;Sharangi 2009). Several phytochemicals, such as polyphenols (phenolic acids, flavan-3-ols, flavonols, and flavones) and alkaloids (theobromine and caffeine) (Figure 1), are found in relatively high amounts in tea.…”

Antioxidant capacity and antioxidants of strawberry, blackberry, and raspberry leaves

“…As mentioned above, green tea is probably the most efficient source of antioxidants in our diet (Lin et al 1996;Kris-Etherton et al 2002;Farhoosh et al 2007). However, green tea as well as black tea contains caffeine (Farhoosh et al 2007) and an excessive intake of caffeine can be related to hypertension, dehydration, anxiety, or insomnia (Gardner et al 2007), whereas no adverse effect has been observed on drinking beverages made from leaves of strawberry, blackberry, and raspberry. Therefore, the studied plants may be seen as an attractive alternative source of antioxidants for the group of consumers consciously selecting the intake of higher levels of antioxidants without caffeine.…”

Effect of black tea on the transverse strength of heat-polymerized acrylic resin

“…Theaflavin and thearubigins are polyphenol-class pigment compounds produced during fermentation and play a role in the typical colour of black tea. 8,9 Tea consumption in the world, especially black tea ranks second after water consumption. A study conducted by the UK National Diet and Nutrition Survey (NDNS) with a sample of 7000 adults showed 77% of them drank tea with an average consumption of 2.3 cups (540 ml) of tea per day.…”

“…A study conducted by the UK National Diet and Nutrition Survey (NDNS) with a sample of 7000 adults showed 77% of them drank tea with an average consumption of 2.3 cups (540 ml) of tea per day. 8 The purpose of this study was to determine the effect of black tea on the transverse strength of heat-polymerized acrylic resin.…”