Tea is the second most consumed beverage in the world, second only to water. All tea, including the four main types (black, white, green and oolong) originates from the same plant, Camellia sinensis. Although all tea has the same origin, the differences occur in the harvesting and processing.1
Green tea starts with freshly picking Camellia sinensis leaves and immediately steaming or pan-frying them to halt oxidation and fermentation, which results in a fresher, lighter flavor. White tea is made in a similar fashion using the newest, youngest buds of the plant. The leaves of black and oolong tea wither and then are rolled and crushed. Oolong tea is partially fermented while black tea is fully fermented.1
Matcha tea, which is recently gaining popularity, is finely ground or milled green tea turned into a powder. Traditional matcha tea powder is then sifted into a bowl with hot water until frothy. When drinking matcha, you consume the whole tea leaf instead of just the infusion, which experts say make matcha nutritionally superior to green tea.
Black tea contains 2-3 times more caffeine than green tea.
Herbal tea is made from a variety of plants, herbs and spices and in many countries cannot be called “tea” since it does not come from the Camellia sinensis plant.
This MNT Knowledge Center feature is part of a collection of articles on the health benefits of popular foods. It provides a nutritional breakdown of tea, an in-depth look at its possible health benefits, how to incorporate more tea into your diet and any potential health risks of consuming tea.
Contents of this article:
Nutritional breakdown of tea
According to the USDA National Nutrient Database, one cup of black tea (approximately 237 grams) contains 2calories, 1 gram of carbohydrate, 0 grams of sugar, 0 grams of fiber and 0 grams of protein as well as 26% of daily manganese needs and small amounts of riboflavin, folate, magnesium, potassium and copper.
Unsweetened brewed green tea is a zero calorie beverage.
The caffeine contained in a cup of tea can vary according to the length of infusing time and the amount of tea infused.
Overall, tea contains few calories, helps with hydration and is a good source of antioxidants.
Catechins, potent antioxidants found primarily in green tea, are known for having beneficial anti-inflammatory and anti-carcinogenic properties.3
Possible health benefits of consuming tea
Most available studies on the potential health benefits of consuming tea have used green tea.
A study published in the Journal of Physiological Anthropology looked at the effects of green tea, white tea and water consumption on stress levels in 18 students. The study suggested that both green and white tea had a lowering effect on stress levels, however, white tea had an even greater effect. Larger studies need to be done to confirm this possible health benefit.
Boosting the brain
Some studies suggest that tea may be beneficial in reducing the risk of dementia and even enhancing our brain’s cognitive functions, particularly the working memory.
A 2006 study published in the Journal of the American Medical Association concluded that green tea consumption is associated with reduced mortality due to all causes, including cardiovascular disease.
The study followed over 40,000 Japanese participants between the ages of 40 and 79 for 11 years, starting in 1994.
The participants who drank at least 5 cups of green tea per day had a significantly lower risk of dying (especially from cardiovascular disease) than those who drank less than one cup of tea per day.
Another study found that consuming 10 cups of green tea per day can lower total cholesterol, however, consuming 4 cups or less had no effect.3
Decreasing cancer risk
Epigallocatechin-3-gallate (EGCG) is the most studied and bioactive polyphenol in tea and has been shown to be the most effective at eliminating free radicals.3
According to the National Cancer Institute, the polyphenols in tea have been shown to decrease tumor growth in the laboratory and animal studies and may protect against damage caused by ultraviolet UVB radiation.
In countries where green tea consumption is high, cancer rates tend to be lower. However, it is impossible to know for sure whether it is the green tea that prevents cancer in these specific populations or other lifestyle factors.6
One large-scale clinical study compared green tea drinkers with non-drinkers and found that those who drank the most tea were less likely to develop pancreatic cancer, particularly women, who were 50% less likely to develop the disease.
Studies have also shown the positive impacts of green tea on breast, bladder, ovarian, colorectal, esophageal, lung, prostate, skin and stomach cancer.
Other studies have shown a lack of preventative effects of tea on cancer. The amount of tea required for cancer-preventive effects has also varied widely in studies – from 2-10 cups per day.3
In 2005, the FDA stated that, “there is no credible evidence to support qualified health claims for green tea consumption and a reduced risk of gastric, lung, colon/rectal, esophageal, pancreatic, ovarian, and combined cancers.”3
Green tea may have an anti-arthritic effect by suppressing overall inflammation.
According to Registered Dietitian Joy Bauer, “studies suggest that EGCG works to stop the production of certain inflammatory chemicals in the body, including those involved in arthritis. Preliminary research suggests that EGCG and other catechins in tea may prevent cartilage from breaking down, possibly helping to preserve joints longer.”
How to incorporate more tea into your diet
For optimal health benefits, tea should be steeped as long as possible to increase flavonoids and 2-3 cups should be consumed per day, according to Tori Crawford, MS, RD, LD.2
Bottled tea does not seem to be as beneficial as brewed tea and contains smaller amounts of beneficial polyphenols.3
Not only can you drink tea, but also you can incorporate it into your cooking. Check out these healthy and delicious recipes developed by Registered Dietitians that incorporate tea:
Potential health risks of consuming tea
People who are extremely sensitive to caffeine could experience insomnia, anxiety, irritability, or an upset stomachwhen consuming tea. Those taking anticoagulant drugs such as Coumadin/warfarin should drink green tea with caution due to its vitamin K content.7
Tea has been found to decrease the bioavailability of iron when taken with meals. People with a history of iron deficiency should take care to not consume tea when taking iron supplements or an iron-rich meal.1
If taken with other stimulant drugs, tea could possibly increase blood pressure and heart rate.
Green tea supplements contain high levels of active substances that can interact with medications and other herbs and supplements. Green tea supplements are unregulated by the FDA and may contain untested substances with unproven health benefits. Always check with a physician before starting any herb or supplement regimen.
In particular, pregnant or breastfeeding women, those with heart problems or high blood pressure, kidney or liver problems, stomach ulcers, or anxiety disorders should not take green tea supplements or extracts.6
It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with variety than to concentrate on individual foods as the key to good health.