Is Tea Good for You？The Experts Say It Is 喝茶对你有好处？专家说的确如此
Peta Bee 佩塔·比
Have you lost your taste for tea？ A recent Kantar Worldpanel survey for Grocer magazine reported that last year the nation drank nearly 870 million fewer cups of char. Lured by flat whites and espressos， and an endless array of healthier-sounding tea alternatives，we collectively contributed to the steepest decline in our consumption of builders tea in four years.
Forget the fancy alternatives and make your tea black or green， advises Helen Bond， a spokeswoman for the British Dietetic Association. “Although both contain caffeine， its about half the amount per cup compared with coffee，” she says. “It contributes to our daily fluid requirements and is a natural source of fluoride in the UK diet， which， provided you dont add sugar， makes it very good for the strength of our teeth.”
Ian Marber， the nutrition therapist and author of Man Food， says there are many myths about tea that are ill-founded. Regular consumption of two to six cups a day has been shown to reduce the risk of some diseases; it is packed with antioxidants， and the tannins help to remove harmful microbes.
“Black and green tea both contain a unique amino acid， L-theanine， which may affect aspects of brain function，” Marber says. “Plenty of studies show that L-theanine has a significant effect on mental alertness or arousal at levels that are easily achieved through drinking a few cups of tea daily.”
Last year a study part-funded by the British Heart Foundation （BHF） showed that the epigallocatechin-3-gallate （EGCG） compound found in a household brand of green tea could hold powerful benefits， with the potential to break up and dissolve potentially dangerous protein plaques in blood vessels that contribute to heart disease.
Regular black tea has also been shown in some studies to have a beneficial effect on lipid levels and blood pressure. “Most of the reputed health benefits of black and green tea come from their high polyphenol content，” Bond says. “And since tea provides about 80 per cent of the flavonoids in the UK diet， it is clearly an important supplier of nutrients.”
Last year researchers from the University of California and Brown University found that those who drank at least one cup of warm black tea every day to be 74 per cent less likely to develop glaucoma. No similar protection was found with iced tea， or decaffeinated tea or coffee， and it was suggested that the abundance of anti-inflammatory phytochemicals and flavonoids in tea might protect the optic nerve.
Black and green tea are made from the same plant， and differences in their taste and appearance depend on how they are grown and processed. Both contain compounds thought to be beneficial for our gut microbiota.
In the 2016 Flemish Gut Flora Project a group of Belgian researchers from the Flanders Institute for Biotechnology identified tea as important for gut health.“Tea is one of 60 dietary factors identified by researchers as influencing the diversity of our gut，” says Dr Megan Rossi， a research associate in gut health at Kings College London. “The different antioxidants it contains are thought to provide the benefits.”
Green and black tea have been shown to help to fight the flab， and green tea extract was useful in preventing obesity. Mice fed a high-fat diet supplemented with green tea extract gained about 20 per cent less weight than those not given the tea supplement. The tea-consuming mice also had lower levels of inflammation within fatty tissue and the intestine.
Coffee， with its higher amounts of caffeine per cup， can leave us jittery， but green tea contains components that could leave us feeling calmer. Its anti-inflammatory polyphenols， known as catechins， have disease-fighting properties. Another beneficial polyphenol in green tea， EGCG， has been shown to help to relieve symptoms of anxiety and depression.
你不喜欢喝茶了？凯度消费者指数公司最近为《食品商》杂志所做的调查表明，2018年全英国喝掉的茶减少了近8.7亿杯。在澳式白咖啡和意式浓缩咖啡，以及不计其数的一堆听起来更健康的替代饮品的诱惑下，我们共同促成了“建筑工人茶”（袋泡红茶，加牛奶和糖，因受到英国建筑工人的欢迎而得名——本网注）消耗量的四年来最大降幅。
忘了那些花哨的替代饮品，给自己泡杯红茶或是绿茶吧，这是英国营养师协会发言人海伦·邦德给出的建议。她说：“虽然两者都含有咖啡因，不过与咖啡相比，每杯茶中的咖啡因含量约为一半。它有助于满足我们的每日液体所需，也是英国饮食中氟化物的天然来源，在不加糖的情况下，它对强健我们的牙齿很有好处。”
营养师、《人以食为天》一书的作者伊恩·马博说，目前存在许多没有事实依据的关于茶的不实之词。经证明，经常每天喝两到六杯茶可以降低患某些疾病的风险；茶中富含抗氧化剂，而且单宁有助于清除有害微生物。
马博说：“红茶和绿茶都含有一种独特的氨基酸——茶氨酸，它可能影响大脑功能的某些方面。大量研究表明，茶氨酸具有很好的提神醒脑功效，每天喝几杯茶就能轻松达到这样的效果。”
2018年，由英国心脏基金会（BHF）提供部分经费的一项研究显示，在一款普通绿茶中发现的表没食子儿茶素没食子酸酯（EGCG）化合物可能对身体大有助益，它有可能打散并分解血管中具有潜在危险性的蛋白质斑块，这种斑块能增加患心脏病的风险。
一些研究还表明，常喝红茶会对脂质水平和血压产生有益的影响。邦德说：“红茶和绿茶大多数最为人熟知的健康助益源自它们含有的大量多酚。由于茶提供了英国饮食中约80%的黄酮类化合物，它显然是重要的营养素供应来源。”
2018年，加利福尼亚大学和布朗大学的研究人员发现，每天至少喝一杯温热红茶的人患青光眼的可能性降低了74%。没有发现冰茶、脱咖啡因茶或咖啡具有类似的保护作用，据认为，茶中富含的抗炎植物化学物质和黄酮类化合物或许能保护视神经。
红茶和绿茶由同样的植物制作而成，它们在口感与外观上的差异是由种植和加工方式决定的。两者都含有被认为对我们肠道微生物群有益的化合物。
在2016年开展的佛兰芒人肠道菌群计划中，来自佛兰德生物研究所的一群比利时研究人员确定茶对维持肠道健康具有重要作用。伦敦大学国王学院从事肠道健康研究的研究员梅甘·罗西博士说：“研究人员确定有60种饮食因素影响着我们的肠道菌群多样性，茶是其中之一。据信它含有的各种抗氧化剂给身体带来了这些好处。”
绿茶和红茶已被证明有助于对抗肌肉的松弛，此外，绿茶提取物还对预防肥胖很有帮助。喂食了辅以绿茶提取物的高脂饮食的老鼠与没有吃绿茶提取物的老鼠相比，体重少增加了20%。食用了绿茶提取物的老鼠的脂肪组织与肠道内的炎症水平也要低一些。
