Higdon Jane V, Frei Balz
Linus Pauling Institute, Oregon State University, Corvallis, OR 97331, USA.
Crit Rev Food Sci Nutr. 2003;43(1):89-143. doi: 10.1080/10408690390826464.
Increasing interest in the health benefits of tea has led to the inclusion of tea extracts in dietary supplements and functional foods. However, epidemiologic evidence regarding the effects of tea consumption on cancer and cardiovascular disease risk is conflicting. While tea contains a number of bioactive chemicals, it is particularly rich in catechins, of which epigallocatechin gallate (EGCG) is the most abundant. Catechins and their derivatives are thought to contribute to the beneficial effects ascribed to tea. Tea catechins and polyphenols are effective scavengers of reactive oxygen species in vitro and may also function indirectly as antioxidants through their effects on transcription factors and enzyme activities. The fact that catechins are rapidly and extensively metabolized emphasizes the importance of demonstrating their antioxidant activity in vivo. In humans, modest transient increases in plasma antioxidant capacity have been demonstrated following the consumption of tea and green tea catechins. The effects of tea and green tea catechins on biomarkers of oxidative stress, especially oxidative DNA damage, appear very promising in animal models, but data on biomarkers of in vivo oxidative stress in humans are limited. Larger human studies examining the effects of tea and tea catechin intake on biomarkers of oxidative damage to lipids, proteins, and DNA are needed.
人们对茶的健康益处兴趣日增，这使得茶提取物被添加到膳食补充剂和功能性食品中。然而，关于饮茶对癌症和心血管疾病风险影响的流行病学证据相互矛盾。虽然茶含有多种生物活性化学物质，但其儿茶素含量尤其丰富，其中表没食子儿茶素没食子酸酯（EGCG）最为常见。儿茶素及其衍生物被认为是茶具有有益作用的原因。茶儿茶素和多酚在体外是活性氧的有效清除剂，也可能通过对转录因子和酶活性的影响间接发挥抗氧化剂的作用。儿茶素能迅速且大量地被代谢，这一事实凸显了在体内证明其抗氧化活性的重要性。在人类中，饮用茶和绿茶儿茶素后，血浆抗氧化能力会有适度的短暂提升。在动物模型中，茶和绿茶儿茶素对氧化应激生物标志物，尤其是氧化性DNA损伤的影响似乎很有前景，但关于人类体内氧化应激生物标志物的数据有限。需要开展更大规模的人体研究，以考察茶和茶儿茶素摄入量对脂质、蛋白质和DNA氧化损伤生物标志物的影响。
