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Blacktea - helpful or harmful? A review of the evidence. GardnerEJ, Ruxton CH, Leeds AR.Eur JClin Nutr. 2007 Jan;61(1):3-18. Objective:To consider whetherconsumption of black tea has a positive or negative impact onhealth.Design:Databases were searched for relevant epidemiological and clinicalstudies published between 1990 and 2004.Results:Clear evidence was found forcoronary heart disease (CHD), where an intake of >/=3 cups per day relatedto risk reduction. The mechanism could involve the antioxidant action of teapolyphenols. While experimental models have suggested that flavonoidsattenuated cancer risk, epidemiological studies failed to demonstrate a cleareffect for tea, although there is moderate evidence for a slightly positive orno effect of black tea consumption on colorectal cancer. Studies on cancer werelimited by sample sizes and insufficient control of confounders. There ismoderate evidence suggestive of a positive effect of black tea consumption onbone mineral density although studies were few. There is little evidence tosupport the effect of tea on dental plaque inhibition but evidence to supportthe contribution of tea to fluoride intakes and thus theoretical protectionagainst caries. There was no credible evidence that black tea (in amountstypically consumed) was harmful. Normal hydration was consistent with teaconsumption when the caffeine content was <250 mg per cup. A moderatecaffeine intake from tea appeared to improve mental performance, althoughsample sizes were small. There was no evidence that iron status could be harmedby tea drinking unless populations were already at risk fromanaemia.Conclusions:There was sufficient evidence to show risk reduction forCHD at intakes of >/=3 cups per day and for improved antioxidant status atintakes of one to six cups per day. A maximum intake of eight cups per daywould minimise any risk relating to excess caffeine consumption. Black teagenerally had a positive effect on healthLeggil'articolo