How you drink your tea could determine whether you gain or lose heart health benefits

By Faye Chiu, CNN

(CNN) — 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.

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.

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.

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.

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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