Tea has benefits for heart health — but not if it’s scalding hot

My morning routine isn’t complete without two calming yet energizing cups of green tea.

Not only is a cup of tea highly enjoyable, but it has long been associated with health benefits, including a lower risk of heart disease, stroke and dementia . Now, a new study published Wednesday in the Journal of Internal Medicine suggests that how people prepare and drink their tea could also influence their cardiovascular health.

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Over an average follow-up of about nine years, researchers documented more than 14,800 cases of diseases affecting the heart and blood vessels, such as heart attacks, strokes and peripheral artery disease, which involves narrowing of arteries supplying blood to the arms and legs.

Researchers analyzed data from more than 485,000 Chinese adults ages 30 to 79. Participants reported their tea-drinking habits, including how frequently they drank tea, what type they preferred, how strong they brewed it, and how hot they drank it.

To help us understand the findings and what they mean for heart health, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously served as Baltimore’s health commissioner.

CNN: What did this new study find about tea consumption and cardiovascular disease?

Dr. Leana Wen: One major result was that people who drank tea at least three days a week had a roughly 11% lower risk of developing vascular disease compared with those who drank it less frequently. This was after accounting for factors including age, smoking, physical activity, body weight and existing medical conditions — though nonsmokers who habitually consumed tea and had high physical activity had the lowest cardiovascular risk.

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Another interesting result was that moderate-strength tea was associated with lower risk, and black tea was linked to lower risks across more types of cardiovascular disease than green tea. Perhaps most surprisingly, people who reported drinking their tea at a “burning hot” temperature had a 16% higher risk of vascular disease compared with those who did not regularly drink tea. In contrast, people who drank tea at room temperature or hot — but not scalding — had significantly lower risk than those who did not regularly drink tea.

However, a limitation of the research methods was that participants described their preferred drinking temperature through self-reporting, rather than the study authors objectively measuring this factor. What one person considers burning hot may be quite different from another person’s definition. It’s also possible that people who prefer burning-hot tea differ in other ways that influence their cardiovascular risk, such as dietary habits or other lifestyle factors that researchers could not fully account for.

CNN: How is drinking tea beneficial to heart health?

Wen: Tea contains naturally occurring compounds called polyphenols, including flavonoids, that have antioxidant and anti-inflammatory properties. These compounds may help protect the cells lining blood vessels and improve the ability of arteries to relax and expand, which can lower blood pressure and reduce strain on the heart.

Some studies have found that tea consumption can modestly improve blood pressure, cholesterol levels and other markers of cardiovascular health. These effects could help explain why people who regularly drink tea have lower rates of strokes, heart attacks and other serious consequences of cardiovascular disease.

There may also be an indirect benefit when people choose unsweetened tea instead of another drink, such as juice drinks, soda or other sugary beverages. Replacing sugar-sweetened drinks with unsweetened tea reduces added sugar consumption, which can help with weight management and metabolic health and thereby further reduce the risk of cardiovascular disease.

CNN: Does the type of tea make a difference — black versus green tea?

Wen: Black tea and green tea come from the same plant, Camellia sinensis , though differences in how the leaves are processed result in different compositions of polyphenols. Previous studies have found benefits associated with both types of tea. In this study, black tea showed more consistent associations with lower cardiovascular risk, though green tea also showed benefits.

I would not advise someone who enjoys green tea to switch to black tea or vice versa. Both can be part of a heart-healthy diet — especially if people take care to drink them without added sugar.

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CNN: How much tea should people drink? Is there such a thing as drinking too much?

Wen: Among study participants who drank tea at least weekly, the lowest estimated vascular disease risk occurred at approximately six to eight cups per day. Risk began increasing again at very high consumption levels exceeding this number.

People should not interpret this to mean that everyone should aim to drink six to eight cups of tea daily. In fact, people should take care when extrapolating this study to their own habits for a variety of reasons, including that researchers did not use a standardized cup size and their estimates relied on self-reported consumption. The authors themselves specifically cautioned against interpreting this finding as an optimal recommended intake.

Another reason to be wary is that tea also contains caffeine. An 8-ounce cup of black tea typically contains around 30 to 50 milligrams of caffeine. Green tea usually contains less, though most forms are not caffeine-free unless the label explicitly indicates so. The US Food and Drug Administration cites 400 milligrams of caffeine per day as an amount not usually associated with dangerous effects. Pregnant people are advised to limit caffeine intake to 200 milligrams daily, and children should not be consuming caffeinated drinks.

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The 9 best tea kettles you can buy, according to editors and tea industry experts (Courtesy CNN Underscored)

CNN: What advice do you have for people who drink tea regularly or are considering adding it to their diet?

Wen: For practical purposes, people should avoid drinking tea that is hot enough to burn their mouths or throats. Repeated consumption of very hot beverages has also been linked to an increased risk of esophageal cancer . Allowing tea to cool until it can be sipped comfortably can prevent burns and could help preserve its potential cardiovascular benefits.

People can choose unsweetened black, green or other teas according to their preferences, and should be mindful of total daily caffeine intake, especially if they experience sleep problems, anxiety or palpitations.

Those who do not currently drink tea should not feel obligated to start. There are many evidence-based ways to reduce cardiovascular disease risk, including regular physical activity , avoiding smoking, maintaining healthy blood pressure and cholesterol levels, and eating a nutritious diet .

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如果没有两杯既能舒缓身心又能提神的绿茶，我的晨间例行程序就不算完整。

一杯茶不仅令人愉悦，而且长期以来都被认为对健康有益，包括降低患心脏病、中风和痴呆症的风险。如今，周三发表在《内科医学杂志》上的一项新研究表明，人们泡茶和喝茶的方式也可能影响他们的心血管健康。

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研究发现，泡茶可能有助于过滤重金属，这对身体有益。

在平均约九年的随访期间，研究人员记录了超过 14,800 例影响心脏和血管的疾病，例如心脏病发作、中风和外周动脉疾病（包括为手臂和腿部供血的动脉变窄）。

研究人员分析了超过 485,000 名年龄在 30 至 79 岁之间的中国成年人的数据。参与者报告了他们的饮茶习惯，包括饮茶的频率、偏好的茶的种类、冲泡的浓度以及饮用的温度。

为了帮助我们理解这些发现及其对心脏健康的意义，我采访了CNN健康专家莉娜·温博士。温博士是乔治·华盛顿大学的急诊医生和临床副教授，她曾担任巴尔的摩市卫生局局长。

CNN：这项新研究对饮茶与心血管疾病的关系发现了什么？

温莉娜博士：一项重要研究结果是，与饮茶频率较低的人相比，每周至少饮茶三天的人患血管疾病的风险降低了约11%。这是在考虑了年龄、吸烟、体育活动、体重和既往病史等因素之后得出的结论——尽管如此，习惯饮茶且体育活动量大的非吸烟者患心血管疾病的风险最低。

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另一个有趣的发现是，中等浓度的茶与较低的风险相关，而且红茶比绿茶与更多类型的心血管疾病风险降低相关。或许最令人惊讶的是，那些饮用“滚烫”茶水的人，患血管疾病的风险比不经常喝茶的人高出16%。相反，饮用室温或温热（但非烫伤）茶水的人，患血管疾病的风险显著低于不经常喝茶的人。

然而，这项研究方法的一个局限性在于，参与者是通过自我报告来描述他们偏好的饮水温度，而不是由研究作者客观地测量这一因素。一个人认为的“滚烫”可能与另一个人的定义截然不同。此外，喜欢喝滚烫茶的人可能在其他方面也存在差异，例如饮食习惯或其他研究人员无法完全考虑到的生活方式因素，这些因素可能会影响他们的心血管风险。

CNN：喝茶对心脏健康有什么好处？

文：茶叶中含有天然存在的多酚类化合物，包括黄酮类化合物，这些化合物具有抗氧化和抗炎特性。这些化合物有助于保护血管内壁细胞，并改善动脉的舒张能力，从而降低血压，减轻心脏负担。

一些研究发现，饮茶可以适度改善血压、胆固醇水平和其他心血管健康指标。这些益处或许可以解释为什么经常饮茶的人中风、心脏病发作和其他严重心血管疾病的发生率较低。

人们选择不加糖的茶而不是其他饮料，例如果汁饮料、汽水或其他含糖饮料，可能还会带来间接益处。用不加糖的茶代替含糖饮料可以减少添加糖的摄入量，这有助于体重管理和新陈代谢健康，从而进一步降低患心血管疾病的风险。

CNN：茶的种类会有影响吗——红茶和绿茶？

温：红茶和绿茶都来自同一种植物——茶树（Camellia sinensis），但由于茶叶加工方式的不同，其多酚含量也存在差异。此前的研究发现，这两种茶都具有一定的益处。本研究发现，红茶与降低心血管风险的关联性更为显著，但绿茶也显示出一定的益处。

我不会建议喜欢绿茶的人改喝红茶，反之亦然。两者都可以成为有益心脏健康的饮食的一部分——尤其是在饮用时注意不添加糖的情况下。

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医生说，喝多少咖啡才算过量？

CNN：人们应该喝多少茶？喝茶过量会有什么问题吗？

温：在至少每周喝一次茶的研究参与者中，估计血管疾病风险最低的情况出现在每天喝大约六到八杯茶的时候。当饮茶量超过这个数字时，风险又开始增加。

人们不应将此解读为每个人都应该每天喝六到八杯茶。事实上，出于多种原因，人们在将这项研究结果推广到自身习惯时应谨慎，其中包括研究人员未使用标准化的杯子容量，且他们的估算依赖于自我报告的饮用量。作者本人也特别提醒，不应将此发现解读为最佳推荐摄入量。

另一个需要注意的原因是，茶也含有咖啡因。一杯8盎司的红茶通常含有约30至50毫克的咖啡因。绿茶的咖啡因含量通常较低，但大多数绿茶并非完全不含咖啡因，除非标签上明确标明。美国食品药品监督管理局（FDA）指出，每日摄入400毫克咖啡因通常不会产生危险影响。建议孕妇每日咖啡因摄入量限制在200毫克以内，儿童不应饮用含咖啡因的饮料。

莫莉·弗洛雷斯/CNN Underscored

根据编辑和茶叶行业专家的推荐，以下是您可以购买的 9 款最佳茶壶（图片由 CNN Underscored 提供）。

CNN：对于经常喝茶或正在考虑将茶加入日常饮食的人，您有什么建议？

温：实际上，人们应该避免饮用烫伤口腔或喉咙的茶。反复饮用过热的饮品也与食道癌风险增加有关。让茶水冷却到可以舒适啜饮的温度，既能防止烫伤，又能有助于保留其潜在的心血管益处。

人们可以根据自己的喜好选择不加糖的红茶、绿茶或其他茶，但应该注意每日咖啡因摄入总量，尤其是有睡眠问题、焦虑或心悸等症状的人。

目前不喝茶的人不必勉强自己开始喝茶。有很多基于实证的方法可以降低心血管疾病的风险，包括定期进行体育锻炼、避免吸烟、保持健康的血压和胆固醇水平以及食用营养均衡的饮食。

每周精选健康生活小贴士，助您轻松享受美好生活。订阅 CNN 的“更美好的生活”电子报，获取提升幸福感的资讯和实用工具。