Black Tea Review

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http://www.nature.com/ejcn/journal/v61/n1/pdf/1602489a.pdf

Black tea – helpful or harmful? A review of the

evidence

European Journal of Clinical Nutrition (2007) 61,

3–18. doi:10.1038/sj.ejcn.1602489; published online 19

July 2006

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 3 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 <250 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 3 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.