16 Conducted Medical Studies on Tea

I recently spent some time reviewing medical studies on tea and want to show some of the most important ones with you today. These studies were conducted by trusted researchers and provide some insights into the unique effects of tea.

Freshly harvested tea
Freshly harvested tea

Can Tea Help to Prolong Your Life?

Tea drinking reduces the risk of mortality. This fact is easy on the ears to tea drinkers, and it comes from a study of 9,000 seniors aged 80+. There were equally notable changes in adults aged 60 and over, as frequent tea drinkers had a 10% lower mortality risk than infrequent ones.(1)

Another trial looked at 100,000 Chinese men and women and classified them as either habitual tea drinkers (3+ cups a day) or non-habitual tea drinkers (less than 3 times a week).

The former lived 1.21 years longer than the latter. They were also less likely to have any series heart complications. Habitual tea drinkers had a 22% lower risk of death from heart disease/stroke and a 15% overall lower risk.(2)

UK Tea Study

Most major medical tea studies are conducted on Chinese participants, but there are a few exceptions. One of them studied nearly 500,000 men and women in the United Kingdom.(3)

They followed up after around 11.2 years and found lower all-cause mortality in participants who drank 2 or more cups of tea a day. This study focused on black tea, the tipple of choice in the UK, but it noted more consistent results when the tea was consumed without milk or sugar.

In truth, it doesn’t really matter how you drink your tea. Sure, you might get more benefits if you abstain from milk and sugar (likely because the latter is calorific and associated with health problems when consumed to excess), but you’ll still getting benefits from the tea. As long as you’re drinking it and enjoying it, you’re fine.

Cheer up with Tea

Caffeine gets a bad press, and it’s easy to see why, as this common stimulant can cause some health issues when consumed in excess. But in tea, it seems to provide some benefits, as a 2018 report found that rates of depression were lower in tea drinkers.

Surprisingly, it found that caffeine could help with depression. I’ve been there. I know how good a cup of tea can feel after a long day. I also feel like a living variation of the “don’t speak to me until I’ve had my coffee” meme. But this isn’t quite what the study was referring to. It’s talking about actual, clinical depression and the symptoms associated with it. It’s not about making people feel a little better when they sate their caffeine addiction after a long day. It’s about a gradual and deep-seated improvement.

It’s an eye-opener when you consider that caffeine generally has bad connotations. It’s a drug, after all, and a stimulant at that. It’s also addictive and so it needs to be treated with caution. Furthermore, this study was conducted on Korean adults and could have cultural connotations. It doesn’t mean that drinking more coffee or higher strength tea will suddenly improve your mood (although drinking one after a long day can certainly have that effect).(4)

Warnings About the Caffeine in Tea

Consuming caffeine has clear pros and cons. You don’t have to look long and hard to find studies on its benefits, but there are also reports suggesting it causes heart problems. They are even easier to find! (5)

However, most of those issues stem from the use of caffeine pills/energy drinks/high-strength coffee. Tea doesn’t have nearly as much caffeine.

Many varieties of tea have an average of 14 to 61mg per cup. This is true for white, green, black, and dark tea, with the latter having the highest concentration. A “moderate” amount of caffeine is between 50 and 300mg a day. So, if an individual were to drink strong black tea, they could drink 5 cups per day without exceeding the safe levels according to medical tea studies.(6)

Conversely, energy drinks can contain around 170mg per can, which means just 2 cans are enough to exceed those safe levels.(7)

Drinking Fermented Tea Could Be Beneficial

Kombucha is a fermented tea that has recently surged in popularity. It’s tangy, naturally low in sugar, and could provide some health benefits. It’s also delicious and is usually a big hit with tea drinkers. Unfortunately, while we’ve been consuming kombucha for thousands of years, empirical evidence is a little thin on the ground, to say the least.(8)

However, we know that the drink has many beneficial compounds. You don’t have to look far to see the benefits of fermented foods either, and I’m not just talking about those commercials of surfing/skating men and women who drink a shot of yogurt and turn into middle-aged superheroes! (9)(10)

Tea and Blood Pressure

In 2020, researchers pored through 1119 trials to find links between tea and blood pressure. They used strict criteria to narrow their search down to just 5 trials, covering 408 individuals. They analyzed tea consumption among in the group and found that regular tea drinking could reduce both diastolic and systolic blood pressure. The longer the habit, the more notable the benefits.(11)

After adjusting for different types of tea, green tea delivered more noticeable results than black tea.

Tea May Have a Positive Impact on Heart Disease

High blood pressure is a symptom of cardiovascular disease, so it’s no surprise that tea consumption has been linked with reduced rates of this chronic illness.

A study of over 37,000 Dutch people looked at the cardiovascular effects of tea consumption over many years. Participants were questioned and then observed for 13 years to measure incidents of cardiovascular morbidity and mortality.

Tea drinkers were much less likely to suffer cardiovascular incidents. What’s more, the researchers found that those consuming 6 or more cups a day were less likely to be diagnosed with coronary heart disease. There was also a reduced risk for coffee drinkers, but no links were found between coffee/tea and strokes.(12)

Tea’s Effect on the Throat

Do you drink your tea with milk? Do you brew at a slightly lower temperature (recommended for white and green tea) or go all-out at 100°C? It impacts taste. It may also reduce your life expectancy (which goes against what I mentioned above) and it’s largely down to the liquid’s heat according to one medical study on tea. (13)

Tea tastes differ based on country and culture. In many English-speaking countries, including the United Kingdom, Australia, and the United States, black tea is the preferred tipple and it’s often consumed boiling with milk/cream. Many drinkers also choose to let the liquid cool before it’s drunk.

In Russia, South America, and the Middle East, tea is often consumed very hot.

Tea itself isn’t the problem. Rather, it’s the damage that the hot liquid causes to the lining of the esophagus, damage that can mount and cause problems in the long term. It’s fair to assume that the same risks would be posed to coffee and hot chocolate drinkers, assuming they consumed their beverages at high temperatures and on a regular basis.

You can negate these risks by drinking your tea at cooler temperatures. For instance, the best temperature for brewing green tea is around 80°C. After giving it sufficient time to brew, it should have cooled to a much more tolerable level. As for black tea, while it’s usually brewed at between 95 and 100°C, it’s best when brewed for 3 to 5 minutes and many drinkers choose to add milk/cream and then wait before drinking. This should be sufficient to drop the temperature.

Green Tea Extracts and Liver Failure

In 2018, the BBC reported on a middle-aged man, Jim McCants, who was left needing a liver transplant after taking supplements; a 16-year-old boy taking green tea supplements was admitted to hospital with an array of issues. These reports makes for stark and very concerning reading if you take these supplements on a regular basis. (14)(15)

The issue is not the tea itself, or even the extracted compounds. It’s the way that these compounds interact with the body when they are consumed in synthetic form, with one study finding that “chronic consumption of synthetic antioxidants has been linked to various diseases”. (16)

Summary: Medical Tea Studies

With thousands of years and billions of drinkers to draw upon, there are innumerable studies concerning tea drinking. The bulk of these highlight its health benefits, focusing on reduced mortality risk and improved heart health, but moderation is key, as there are also studies warning against excessive use of green tea supplements and the consumption of boiling hot tea.

These medical studies on tea are fascinating. My eyes were opened to the many ways that tea influences the mind/body. It’s one of the most popular beverages in the world. Drinking tea is a habit that many people have. And unlike many other popular drinks—beer, wine, soda—it’s a habit that’s worth having.

If you’re interested in learning more about tea, check out some of these studies yourself. You can find links to all of them below.