There is plenty to enjoy in a plain cup of green tea: the aroma of the leaves, the flavour and the simple act of making it. Research also gives us specific findings to explore. Here we look at what human studies have measured, how those results relate to an ordinary cup, and how caffeine fits into your day.
Start with the drink in your cup
For a plain, unsweetened cup, brew unflavoured leaves or a tea bag in water, then decide whether you want to add anything. With a prepared or bottled drink, check the ingredients rather than relying on the tea name.
Keep three categories separate: a brewed infusion, a prepared drink, and a concentrated extract or capsule. For a matcha-based drink, check what else has been added. These products can differ in composition and portion size, so research on one cannot simply stand in for research on another.
Get to know the compounds in tea
Green tea comes from Camellia sinensis, the plant also used for black and oolong tea. It contains caffeine and catechins, a group of plant compounds. EGCG is one catechin you may see mentioned in research or on supplement labels.
Knowing that a compound is present does not tell you the amount in your cup or establish a health benefit. The product and the way it is prepared still matter. For your daily cup, there is no need to chase a more concentrated drink because a compound has made the headlines.
Choose a time for your tea
Green tea contains caffeine, and the amount varies with the product and preparation. Consider it alongside coffee and other sources of caffeine in your day, and pay attention to your own sensitivity and drinking time.
Tea colour and cup size alone cannot give you an exact caffeine amount. Decaffeinated tea still contains some caffeine. If a late drink affects your sleep, move your tea break earlier or choose a caffeine-free drink.
Read a study with four questions
Before turning a tea headline into a reason to buy, look at what the study actually tested. A brewed drink, powder and concentrated preparation can have different compositions and amounts. Then ask four questions.
1. What was tested: a drink, powder or concentrated extract?
2. Who took part, and are their circumstances relevant to yours?
3. What was measured: a laboratory result, a blood marker or health over time?
4. Are the findings consistent across studies and over time?
These answers help you judge how much weight to give a finding. Keep the measured outcome separate from what you hope to experience.
What human studies have found
Human research has produced some encouraging findings. A review of randomized trials of green tea preparations, published in Nutrition Journal 19, 48 (2020), found small average reductions in total and LDL cholesterol compared with controls. Most of its comparisons used extract capsules, doses varied and many trials were judged at high risk of bias. The research measured blood markers; it did not establish that ordinary green tea prevents heart disease.
Weight research gives us a more modest picture. Some studies of catechins and caffeine have reported small changes, but in a Cochrane review of green tea preparations for weight loss and maintenance in adults with overweight or obesity, the changes with tested green tea preparations were small and unlikely to be clinically important. Weight maintenance did not show a significant benefit. This research does not provide a slimming dose or brew recipe for an ordinary cup.
Make your next cup an easy choice
At the kettle or in the shop, make three choices: plain or sweetened, a suitable time for caffeine, and a flavour you enjoy.
Choose a flavour you look forward to and prepare it to suit your taste. A stronger brew or a large daily total is not a goal in itself. Keep the choices that make the tea enjoyable for you.
Give supplements a separate safety check
Concentrated supplements need their own safety assessment. They are different products from brewed tea, with different concentrations and potential risks.
If you take medicines, have a medical condition, are pregnant or are breastfeeding, ask a qualified health professional about drinks and supplements that suit your circumstances. Mention all your caffeine sources and any supplements.
Questions & answers
Should I choose plain tea or a sweetened drink?
If you want to avoid adding sugar or syrup, a plain infusion is a straightforward option. For prepared or bottled tea, check the actual ingredients and added sugar rather than relying on its name.
Is there a number of cups I should aim for?
There is no single cup target in this guide. Consider the product, portion, caffeine from other sources and your circumstances. Ask a health professional if you need individual advice.
Can I use an extract instead of drinking tea?
An extract is a different product, with different concentrations and potential risks. Do not assume it offers the same experience or outcome as brewed tea. Ask a health professional before using supplements, particularly alongside medicines.