Tea and Cancer

Abstract

Tea is one of the most popular beverages consumed worldwide. The relationship between tea consumption and human cancer incidence is an important concern. This topic has been studied in different populations by many investigators, but no clear-cut conclusion can be drawn. Whereas some studies have shown a protective effect of tea consumption against certain types of cancers, other studies have indicated an opposite effect. Our purpose is to provide a critical review of this topic, covering basic chemistry and biochemical activity of tea, epidemiologic investigations, and laboratory studies, as well as possible directions for future research. Studies have demonstrated either a lack of association between tea consumption and cancer incidence at specific organ sites or inconsistent results. On the other hand, many laboratory studies have demonstrated inhibitory effects of tea preparations and tea polyphenols against tumor formation and growth. This inhibitory activity is believed to be mainly due to the antioxidative and possible antiproliferative effects of polyphenolic compounds in green and black tea. These polyphenolics may also inhibit carcinogenesis by blocking the endogenous formation of N-nitroso compounds, suppressing the activation of carcinogens, and trapping of genotoxic agents. The effect of tea consumption on cancer is likely to depend on the causative factors of the specific cancer. Therefore, a protective effect observed on a certain cancer with a specific population may not be observable with a cancer of a different etiology. On the basis of this concept, we suggest future laboratory and epidemiologic studies to elucidate the relationship between tea consumption and human cancer risk.

Suppression of fatty acid synthase in MCF-7 breast cancer cells by tea and tea polyphenols: a possible mechanism for their hypolipidemic effects

“…16,17,27 The cancer chemopreventive action of tea has been attributed to its major phytopolyphenols. The tea polyphenols comprise about one-third of the weight of the dried leaf, and they show profound biochemical activities including antioxidant activities, 28 modulation of carcinogen metabolism, inhibition of cell proliferation, 20 induction of cell apoptosis 29 and cell cycle arrest.…”

Inhibition of carcinogenesis by tea constituents

“…Some of the results have been reviewed previously [1][2][3][4][5][6][7][8]. Table 1 summarizes the results of 120 studies published since the year 1991.…”

“…In 1991, the Working Group of the International Agency for Research on Cancer (IARC) reviewed the effects of tea on cancers of different sites and concluded that "there is inadequate evidence for the carcinogenicity in human and experimental animals of tea drinking" [58]. In 1993, Yang and Wang reviewed more than 100 published papers and paid more attention to the possible cancer preventive effects of tea consumption [1]. This review summarized that, while some studies showed a negative association between tea consumption and cancer risk, others showed no association or positive association.…”

La restriction calorique chez les primates

“…Elle procure également des effets bénéfiques chez des rats soumis à un régime riche en lipides en diminuant la masse corporelle, la pression artérielle et les pathologies cardiovasculaires [39]. Le thé possède aussi une grande quantité de polyphénols qui auraient des effets protecteurs contre certains cancers [40] et contre le développement de maladies cardiovasculaires [41]. Parallèlement, un analogue du sucre est à l'étude, le 2-déoxyglucose, qui agit comme un inhibiteur glycolytique.…”