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2006年10月8日 周日

    伊斯兰堡：有证据表明每日饮至少4杯红茶能帮助你消除日常生活中的压力。传统观点认为，茶可以缓解压力，许多人相信饮料可以帮助他们放松，但关于茶能促进放松的科学证据却不多。

    在一项新的研究中，伦敦大学的研究人员将75位常饮茶的年轻男性分成了两组，并且对他们进行了为期6周的监测。他们的研究结果公布在了大学的网页上。其中一组给予水果口味含有咖啡因的茶（是一般红茶的构成成分），另一组给予与前组相同味道但无咖啡因的安慰剂。两组实验对象都给予了同样的任务，同时监测了他们体内的皮质醇、血压、血小板、并纪录了他们自己描述的压力程度。

    一项任务中，受试的志愿者被置于三种紧张的环境中（解雇的威胁，入店行窃的指控及养老院中发生的事故），然后他们必须在镜头前准备一个口头的回答和辩论。此项任务引起了两组对象血压，心率和自我主观压力感的增高，也就是说两组的压力程度很相似。然而，实验后的50分钟，饮用红茶组的受试对象中皮质醇平均下降了47%，但假红茶饮用组则只下降了27%。

     研究者还发现，在饮用红茶的对象中，与血栓形成和心脏疾病相关的血小板的激活明显较低，而且他们在完成任务后的恢复期能更好地放松。

    UCL 教授Andrew Steptoe说，这是迄今为止第一次在双盲实验中评价了茶的作用，无论是我们或受试者都不知道他们饮用的是什么。“我们确实不知道是茶中的何种成分起到了抗压力促进放松的作用。茶的化学成分非常复杂，含有许多不同的成分。”“其中许多成分如儿茶酚，多酚，类黄酮和氨基酸都发现对脑中的神经递质有作用，但此项实验并不能说明是哪个物质起到了作用”，研究人员表示。

    “不过，我们的实验提示，饮茶能让我们从日常的生活压力中更快地恢复。虽然这并不能减轻我们经历的压力的程度，但却能更快地使参与应激反应的激素恢复正常。”Steptoe认为应激后的快速恢复有着非常重要的意义，否则会增加许多慢性疾病如心血管疾病的发生风险。

Fight stress with four cups of black tea a day
Sunday October 08, 2006 (0623 PST)

ISLAMABAD: Drinking at least four cups of black tea a day could help you fight the stresses of everyday life, evidence shows.
Tea has traditionally been associated with stress relief, and many people believe that the beverage helps them relax after facing the stresses of everyday life. However, scientific evidence for the relaxing properties of tea is quite limited.

In the new study, researchers at London?s University College studied 75 young male regular tea drinkers splitting them into two groups and monitored them for six weeks, states a release posted in the university website.

While one group was given a fruit-flavoured caffeinated tea mixture made up of the constituents of an average cup of black tea, the other was given a caffeinated placebo identical in taste but devoid of the active tea ingredients.

Both groups were subjected to challenging tasks, while their cortisol, blood pressure, blood platelet and self-rated levels of stress were measured.

In one task, volunteers were exposed to one of three stressful situations (threat of unemployment, a shop lifting accusation or an incident in a nursing home), where they had to prepare a verbal response and argue their case in front of a camera.

The tasks triggered substantial increases in blood pressure, heart rate and subjective stress ratings in both of the groups. In other words, similar stress levels were induced in both groups. However, 50 minutes after the task, cortisol levels had dropped by an average of 47 percent in the tea drinking group compared with 27 percent in the fake tea group.

Researchers also found that blood platelet activation - linked to blood clotting and the risk of heart attacks - was lower in tea drinkers, and that this group reported a greater degree of relaxation in the recovery period after the task.

This is one of the first studies to assess tea in a double-blind placebo controlled design - that is, neither we nor the participants knew whether they were drinking real or fake tea, UCL Professor Andrew Steptoe said.

"We do not know what ingredients of tea were responsible for these effects on stress recovery and relaxation. Tea is chemically very complex, with many different ingredients.

"Ingredients such as catechins, polyphenols, flavonoids and amino acids have been found to have effects on neurotransmitters in the brain, but we cannot tell from this research which ones produced the differences," the researcher said.

"Nevertheless, our study suggests that drinking black tea may speed up our recovery from the daily stresses in life. Although it does not appear to reduce the actual levels of stress we experience, tea does seem to have a greater effect in bringing stress hormone levels back to normal."

This has important health implications because slow recovery following acute stress has been associated with a greater risk of chronic illnesses such as coronary heart disease, Steptoe said.

http://paktribune.com/news/index.shtml?156470

编辑：蓝色幻想