Tea is the second most consumed beverage in the world after water. All tea comes from the Camellia sinensis plant, but different ways of harvesting and processing the plant produce different types of tea.
After harvesting, black tea leaves go through a process of wilting, bruising, rolling, and oxidation.
Oxidation occurs when the leaves remain exposed to the air for a long time. Enzymes break down the chemicals in the leaves, producing their brown coloring and familiar smell.
The process for making green tea is similar, but it does not involve oxidation. Oxidation may give black tea nutritional benefits that are not present in green tea.
In this article, learn more about the benefits of drinking black tea, as well as the nutrients it provides and the possible risks.
According to the United States Tea Association, black tea accounted for around 84% of tea consumption in the U.S. in 2018.
Black tea may have similar benefits to green tea. However, many studies have looked specifically at black tea, and how the oxidation process may impact health.
A key area of interest is black tea as a source of antioxidants.
Antioxidants help combat free radicals. Free radicals are unstable molecules in the body that result from both natural processes and environmental pressures.
The body can remove free radicals, but if too many build up, they can damage or change cells in the body.
These changes can contribute to the development of many diseases and conditions, such as atherosclerosis and some cancers.
Antioxidants can help remove free radicals, and tea is one source of antioxidants. In fact, one study notes that phenolic compounds, which have antioxidant effects, constitute up to 30% of the dry weight of green and black tea.
The antioxidants in black tea are different from those in green tea, due to the oxidation process. Green tea mainly contains catechins. During oxidation, these convert into thearubigins, theaflavins, and flavonols.
These may give black tea different benefits to green tea.
Protecting against atherosclerosis
A 2004 hamster study suggested that consuming black tea or green tea at human equivalent doses might prevent the development of atherosclerosis. More research is necessary in humans to confirm this.
One review suggests that drinking three or more cups of tea per day might help protect against coronary heart disease.
However, it is important to note that black tea contains caffeine, and drinking more than three cups per day would contribute a significant amount of caffeine to a person's daily intake.
In 2013, researchers found evidence to suggest that people who drank four cups of black tea or more per day had a lower risk of stroke.
Lowering cancer risk
More studies are needed, however, to confirm whether or not drinking tea as part of the diet can help reduce the risk.
How can diet affect cancer? Find out here.
Reducing blood pressure
The findings of a 2015 study suggested that black tea may reduce diastolic and systolic blood pressure.
Consuming black tea also appeared to cancel out the impact of a high fat meal on blood pressure.
This benefit remained despite the caffeine content of the tea. However, this was a small study with only 19 participants, so larger studies are necessary to confirm these results.
In this article, learn more about foods that help lower blood pressure.
Protecting against diabetes
Some research has suggested that consuming tea might help reduce the risk of diabetes.
In one study, people with type 2 diabetes consumed different amounts of black tea extract over a period of 4 weeks. The authors concluded that regular consumption of black tea might have antioxidative and anti-inflammatory effects for people with this condition.
Benefits for other conditions
However, more studies are needed to confirm these findings.
The NCI note that tea contains:
- alkaloids, including caffeine, theophylline, and theobromine
- amino acids
- minerals and trace elements
- volatile organic compounds, which contribute to its odor and taste
The antioxidant effect of black tea is due to its polyphenol content. Polyphenols are chemical compounds that protect plants from ultraviolet radiation and harmful, disease-causing pathogens.
Flavonoids are one type of polyphenol. They occur in grapes, red wine, and other foods.
The antioxidant effect of polyphenols may help protect the body from changes that lead to disease.
Which foods are good sources of antioxidants? Find out here.
Consuming black tea can be a healthful way to provide a daily caffeine boost. The tea is low in calories, especially when a person does not add sugar.
Ways of adjusting the flavor without adding sugar or sweeteners include:
People can also use it in cooking. For example, they can use it:
As a stock: Black tea can add a smoky flavor to soups with red meat or mushrooms.
In poaching liquids: Poaching food in black tea infuses the aroma into the food. One idea is to poach mushrooms in lapsang souchong black tea.
For cooking beans and grains: Swapping water for tea when cooking rice or beans adds a smoky nuance to their flavor.
In desserts: Infuse the flavor of tea into warm milk and add to puddings or custards. Or, infuse Earl Grey black tea into a chocolate mousse.
There may be some risks to drinking black tea. The following sections discuss these risks in more detail.
All brewed tea contains minerals that, in excess, can be poisonous.
Lead and aluminum are present in tea. In large doses, these heavy metals can be toxic to humans. Minor traces of arsenic and cadmium can also be present in some teas, but not in harmful quantities.
Black tea also has high levels of manganese. The body needs this mineral, but it can be toxic in excess.
The longer tea brews, the higher the concentration of these toxic elements will be. Brewing tea for a maximum of 3 minutes can reduce the risks.
Depending on where and how people grow the tea, there may also be traces of pesticides in the leaves. This is another reason for people to limit the amount of tea they consume each day.
What is lead poisoning? Find out here.
Effects of caffeine
Black tea contains around 2–4% caffeine.
Consuming too much caffeine may also lead to:
- cardiac arrhythmia, or an irregular heartbeat
- diarrhea and irritable bowel syndrome
- eye pressure, and possible glaucoma
- an increase or decrease in blood sugar
- an increase in blood pressure
- a loss of calcium through the urine, which could lead to weakened bones and possible osteoporosis
People who drink tea regularly and who experience any of the above symptoms should consider reducing their tea consumption. If symptoms continue, they should see a doctor.
Learn more about caffeine consumption here.
Black tea contains tannins. One 2017 review found that tannin-rich foods, such as tea, may be a good source of antioxidants, but that they can also reduce the body's ability to absorb iron.
For this reason, people with a history of iron deficiency should avoid consuming tea when taking iron supplements or eating an iron-rich meal.
They should also leave an hour between eating and drinking black tea.
Interactions with drugs and supplements
Black tea and the caffeine it contains may interact with a range of different medications and supplements.
These medications include but are not limited to:
Adenosine: Doctors give this drug before a cardiac stress test.
Antibiotics: Some types of antibiotic affect the way the body breaks down caffeine.
Carbamazepine (Tegretol): Caffeine may reduce this drug's effectiveness in preventing seizures.
Ephedrine: This, like caffeine, is a stimulant. Taking them together might therefore trigger side effects.
People who use medications should speak to their doctor about their caffeine intake through tea or coffee. It could impact how their drugs work and their risk of adverse effects.
Iced teas and ready-to-drink teas may be less healthful than plain black tea, as the composition is different. Instant and flavored teas may contain sugar and other ingredients.
Adding sugar, milk, cream, and syrups to tea increases the calorie content and may reduce its health benefits.
Black tea is a popular drink worldwide, and it may have some health benefits. It is also low in calories.
People who drink a lot of tea — especially with added milk, sweeteners, or syrup — should bear in mind the possible risks, such as the high caffeine and sugar intake.
They may also wish to ask their doctor if a high intake of black tea is likely to interfere with any medications they are taking or affect other aspects of their health.