Chemopreventive effects of tea in prostate cancer: green tea versus black tea.

The polyphenol compositions of green tea (GT) and black tea (BT) are very different due to post-harvest processing. GT contains higher concentrations of monomeric polyphenols, which affect numerous intracellular signaling pathways involved in prostate cancer (CaP) development. BT polymers, on the other hand, are poorly absorbed and are converted to phenolic acids by the colonic microflora. Therefore, after consumption of GT higher concentrations of polyphenols are found in the circulation while after BT consumption the phenolic acid levels in the circulation are higher. The majority of in vitro cell culture, in vivo animal, and clinical intervention studies examine the effects of extracts of GT or purified (-)-epigallocatechin-3-gallate (EGCG) on prostate carcinogenesis. These studies provide strong evidence supporting a chemopreventive effect of GT, but results from epidemiological studies of GT consumption are mixed. While the evidence for a chemopreventive effect of BT is much weaker than the body of evidence with regard to GT, there are several animal BT intervention studies demonstrating inhibition of CaP growth. This article will review in detail the available epidemiological and human clinical studies, as well as animal and basic mechanistic studies on GT and BT supporting a chemopreventive role in CaP.

由于采后加工的不同，绿茶（GT）和红茶（BT）的多酚成分差异很大。绿茶含有较高浓度的单体多酚，其影响众多参与前列腺癌（CaP）发展的细胞内信号通路。另一方面，红茶聚合物吸收不良，并被结肠微生物群转化为酚酸。因此，饮用绿茶后，血液中发现的多酚浓度较高，而饮用红茶后，血液中的酚酸水平较高。大多数体外细胞培养、体内动物和临床干预研究都考察了绿茶提取物或纯化的（-）-表没食子儿茶素 - 3 - 没食子酸酯（EGCG）对前列腺癌发生的影响。这些研究提供了强有力的证据，支持绿茶的化学预防作用，但关于饮用绿茶的流行病学研究结果喜忧参半。虽然红茶化学预防作用的证据比绿茶的相关证据弱得多，但有几项动物红茶干预研究表明其对前列腺癌生长有抑制作用。本文将详细回顾现有的流行病学和人体临床研究，以及关于绿茶和红茶在前列腺癌中具有化学预防作用的动物和基础机制研究。