Green tea (Camellia sinensis)

Green tea is derived from the shrub Camellia sinensis, the same plant as used for black tea, but is not fermented.

A 2009 Cochrane review of 51 randomized clinical trials, observational studies and case-control studies with over 1.6 mio participants concluded that there is insufficient and conflicting evidence to establish an association between green tea consumption and the incidence of cancer.1

One earlier systematic review including 43 epidemiological studies, 4 randomized trials and 1 meta-analysis with the overall quality as good or moderate found that some evidence suggested that green tea might have beneficial effects on gastrointestinal cancers, but the findings were not consistent.2

Four other systematic reviews on the risk association between green tea and lung cancer3, breast cancer4, colorectal cancer5 and stomach cancer6 respectively found inverse association between green tea consumption and cancer incidence but the studies were generally associated with heterogeneity.

Although the majority of the studies show that long-term consumption of large amounts of green tea may prevent the occurrence of some forms of cancer, the findings of both cohort studies and case-control studies are inconsistent.

Drinking green tea appears safe at regular, habitual and moderate use (3-9 cups per day).