For millennia, people have been enjoying the rich scents and tastes that tea affords. Originating from East and South Asia, tea is now the most consumed drink in the world next to water. This aromatic drink has long been touted for its healing powers, as described in ancient Chinese legends … but is tea good for you? And is green tea all that special? In this article, we will first cover how tea is prepared from tea leaves. Next, we’ll talk about what makes green tea different from other kinds of teas (green tea vs. black tea). Finally, we’ll talk about the myriad health benefits that green tea appears to provide compared with other drinks, such as does green tea have caffeine and green tea for weight loss.

How is tea prepared?

All tea is derived from the tea plant Camellia sinensis, yet thousands of tea varieties exist. The secret to this diversity lies in the many preparation methods used to prepare tea. Although all teas are prepared by adding leaves into boiling water, the types of teas produced depend on how the tea leaves are prepared after harvest. After the leaves are plucked from a tea plant, a series of steps determines the taste and nutritional content of the tea:

• Withering is the process in which leaves are dried under the sun or in a well-ventilated room. This process induces a series of molecular changes to the withered leaf — including increased caffeine content, breakdown of carbohydrates and proteins into their constituent sugars and amino acids, and production of other volatile compounds.
  
  
• Bruising is the step in which the tea leaves are crushed, rolled or shaken. The mechanical process breaks down the internal structures of the leaf. This can change flavor profiles and further promote leaf oxidation.
  
  
• Oxidation exposes tea leaves to oxygen to dry and darken them. These reactions further alter the chemical composition of the leaves, affecting the flavor and aromas generated.
  
  
• Drying is a process that stabilizes the tea leaves for storage and flavor enhancement. It effectively stops the oxidation process and makes them ready for brewing tea.

Teas prepared from leaves are also distinct from herbal teas. Unlike true teas which are produced from Camellia sinensis leaves, herbal teas are produced from blends of other leaves, fruits, bark, roots, or flowers belonging to any other edible plant.

What is green tea?

What about green teas makes them so special? One of many tea varieties, green tea was first brewed in China’s Yunnan Province nearly 5,000 years ago. Unlike other kinds of tea, green tea does not undergo a withering and bruising process. Instead, the leaves of the tea plant are immediately dried. That’s why green tea is considered the least processed tea. As a result, green tea retains many of the compounds that hold the tea leaves together. This, in turn, helps green tea retain its freshly picked flavor and prevents oxidation from occurring. Many kinds of green tea — including sencha, jasmine, and longjing — exist, depending on how the leaves are cultivated.  

Why is green tea more potent than other teas?

Since tea types are distinguished by their preparation methods, it’s likely that different kinds of teas have varying chemical compositions, affecting your body in different ways. For green tea, the fact that it is less oxidized means that green tea retains more of the most beneficial compounds: 

• High polyphenol content (~30% of total dry weight): Of the teas, green tea contains the highest polyphenol concentration because the immediate heating of the leaves prevents the oxidation process from breaking down its polyphenols. The higher concentration of polyphenols contributes to green tea having higher antioxidant capabilities than black tea. The elevated antioxidant properties may also contribute to green tea conferring protective benefits against different kinds of cancer — including oral, ovarian, endometrial and lung cancer.
  
  
• High catechin content: It’s not just the high polyphenol content that distinguishes green tea from other teas. Approximately 80-90% of the flavonoids in green tea, the most notable kind of polyphenol, are catechins. This is in contrast with other kinds of drinks. For instance, coffee and black tea contain high concentrations of chlorogenic acid and theaflavins, respectively. Of the catechins, green tea is richest in epigallocatechin-3 (EGCG).

Does green tea have caffeine?

Ever thought, "does green tea have caffeine?" Some people may feel concerned about the caffeine present in green tea. Having too much caffeine can lead to a number of side effects — such as increased anxiety, risk of insomnia and digestive issues. However, the concentration of caffeine in green tea is lower than that found in a cup of coffee or even black tea. Furthermore, (and contrary to popular belief), although caffeine makes you urinate more, caffeine intake does not lead to dehydration,.

However, there are cases in which the caffeine in green tea may be a concern. For instance, some medications can interact with caffeine, leading to increased blood pressure or worsened side effects. If you are concerned about the levels of caffeine in your green tea, you can also prepare a decaffeinated cup of green tea. Just note, however, that every decaf brand will still contain trace amounts of caffeine: 2 mg per 8 oz cup of green tea.

How much caffeine does green tea have?

The next question you'll probably ask yourself is: "how much caffeine does green tea have?" A single cup (8 oz) of green tea contains 30 to 50 milligrams (mg) of caffeine. This concentration is half that observed in a single cup of coffee ( 95 mg of caffeine per cup) and less than what is observed in black tea (39-109 mg per 8 oz cup).

Green tea vs. black tea and other teas

Green tea, thanks in part to the unoxidized nature of its leaves, contains high concentrations of polyphenols and catechins. While the data remains inconclusive regarding the precise health benefits of these substances, there is research to suggest that they may reduce the risk of certain cancers, aid in weight loss, protect against cardiovascular diseases and improve metabolic health. So when comparing green tea vs. black tea vs. other types of teas, research points to green tea being a clear step ahead when it comes to health benefits:

Green tea for cancer

A 2005 meta-analysis of 13 studies determined that people who drank green tea had a lower risk of breast cancer. Another 2009 meta-analysis of 22 studies determined that consuming green tea reduced the risk of lung cancer compared with black tea. A more recent meta-analysis, however, pointed to the inconsistent nature of green tea’s benefits against cancer. Thus, more research is needed in this area.

Green tea for weight loss

A 2020 meta-analysis of 25 eligible studies suggested that consuming green tea can help manage obesity when combined with a healthy diet and regular exercise. This result contrasts with a 2012 meta-analysis of randomized control trials (RCTs) that showed a small, but non-significant correlation between green tea consumption and weight loss. The presence of different polyphenols in green tea and black tea may affect their weight management benefits. Black tea seems to be more effective than green tea, possibly because the polyphenols in black tea may be better at inhibiting enzymes that break down fats. Thus, while green tea may provide weight loss benefits, black tea may actually be better. If you're looking for the best green tea for weight loss, then, it may be worthwhile selecting black tea for this specific use case.

Green tea for cardiovascular disease (CVD)

A 2015 meta-analysis showed a reduced risk of coronary heart disease with increasing consumption of either black or green tea. Another meta-analysis supported these findings, showing that green tea consumption was correlated with improved CVD and ischemic-related disease outcomes. Among the herbal teas, hibiscus tea may also help lower blood pressure, acting as a good alternative for those individuals concerned about the caffeine levels in green tea.

Green tea for diabetes

A 2013 meta-analysis determined that green tea consumption was associated with reduced fasting blood glucose levels — important for reducing the risk of T2D (and for better management of the disorder) — whether caffeine was present or not. (Similarly, coffee consumption, whether decaffeinated or with caffeine, was shown in a 2014 meta-analysis to have a significant dose–response reduction in T2D risk. Researchers hypothesize that, as in the case of green tea, it is probably the other bioactives, many of which are antioxidants, in coffee and tea, rather than the caffeine, that protects against type 2 diabetes. Learn more in our report, Coffee And Diabetes.) If caffeine is a concern, the small amount of studies for herbal tea suggests that drinking herbal tea could also reduce T2D risk, as well as encourage weight loss.

Part of the problem scientists face when attempting to prove the benefits of green tea lies in the large quantity of different green tea brands and varieties. Different green tea brands from Thailand have varying concentrations of caffeine and polyphenols. Changes in climate and altitude also affect catechin concentrations; rising temperatures may deteriorate green tea quality over time. Catechin concentrations can also change in the midst of conducting an experiment of green tea’s health benefits. Each of these variables also impacts caffeine content in green tea, which can vary by brand depending on brewing time. Even so, the early research into green tea’s benefits is considered promising, although much more research is needed to clarify findings and better explain mechanisms and causality. 

Key takeaways

Green tea is a drink originating in Asia that is now enjoyed the world over. The fact that thousands of tea varieties can form from a single tea plant is a testament to the intrinsic beauty of this ancient drink. If you want to have a nice cup of green tea, go ahead and drink a cup with your meal. At the very minimum, it will provide a soothing aroma for your nose and palette. On top of that, green tea appears to provide distinct health benefits that most other kinds of tea and many other beverages do not, including protective effects against cardiovascular diseases, certain cancers and aid in weight loss. Does green tea have caffeine, though? The answer is yes, but not as much as other teas and coffee. If you’re still concerned about caffeine levels, you can still get similar health benefits from drinking a decaffeinated green tea or a herbal tea.