According to a study published in the European Journal of Clinical Nutrition, drinking just three cups of black tea per day significantly reduces the risk of coronary heart disease.
Authors E J Gardner, C H S Ruxton and A R Leeds said that their search of databases for relevant epidemiological and clinical studies published between 1990 and 2004 suggested that the mechanism responsible could involve the antioxidant action of tea polyphenols.
The study, sponsored by the Tea Council and designed to review the evidence of whether consumption of black tea has a positive or negative impact on health, was not so clear in relation to cancer.
“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,” they reported. Studies on cancer were limited by sample sizes and insufficient control of confounders.
However, the authors found positive benefits from black tea consumption for bone mineral density, mental performance, and general health, and no suggestions of harmful effects.
“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,” they reported. “There was no evidence that iron status could be harmed by tea drinking unless populations were already at risk from anaemia.”
Normal hydration was consistent with tea consumption when the caffeine content was <250 mg per cup.
The report concluded that there was sufficient evidence to show risk reduction for coronary heart disease 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,” they said. “Black tea generally had a positive effect on health.”