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Two common types of caffeinated tea, green tea and black tea, are made from the leaves of Camellia sinensis. The difference between these two teas is the degree of oxidation they undergo in air before drying. Generally speaking, black tea is fermented (meaning the sugar  molecules are broken down through natural chemical processes) but green tea is not. Camellia sinensis was the first cultivated tea tree in Asia and has been used as a drink and medicine for thousands of years.
Both green and black tea contain polyphenols, plant compounds whose antioxidant and anti-inflammatory properties have been studied. Read on to learn more about the common and unique benefits of these teas.
Danielle Crumble Smith, a registered dietitian at Vanderbilt Monroe Carell Jr. Children’s Hospital in the Nashville area, says the way green and black tea are processed causes each type to produce unique bioactive compounds.
Some research suggests that black tea’s antioxidants, theaflavins and thearubigins, may help improve insulin sensitivity and blood sugar control. “Some studies have shown that black tea is associated with lower cholesterol [and] improved weight and blood sugar levels, which in turn may improve cardiovascular outcomes,” says board-certified internal medicine physician Tim Tiutan, Dr. medical sciences. and an attending physician assistant at Memorial Sloan-Kettering Cancer Center in New York City.
Drinking no more than four cups of black tea per day reduces the risk of heart disease, according to a 2022 review of research published in Frontiers in Nutrition. However, the authors noted that drinking more than four cups of tea (four to six cups per day) may actually increase the risk of cardiovascular disease [3] Yang X, Dai H, Deng R, et al. Association between tea consumption and prevention of coronary heart disease: a systematic review and dose-response meta-analysis. Nutrition boundaries. 2022;9:1021405.
Many of the health benefits of green tea are due to its high content of catechins, polyphenols, which are antioxidants.
According to the National Center for Complementary and Integrative Medicine at the National Institutes of Health, green tea is an excellent source of epigallocatechin-3-gallate (EGCG), a powerful antioxidant. Green tea and its components, including EGCG, have been studied for their ability to prevent inflammatory neurodegenerative diseases such as Alzheimer’s disease.
“The EGCG in green tea was recently found to disrupt tau protein tangles in the brain, which are especially prominent in Alzheimer’s disease,” says R.D., a registered dietitian and director of Cure Hydration, a plant-based electrolyte drink blend. Sarah Olszewski. “In Alzheimer’s disease, tau protein abnormally clumps together into fibrous tangles, causing brain cell death. So drinking green tea [may] be a way to improve cognitive function and reduce the risk of Alzheimer’s disease.”
Researchers are also studying the effects of green tea on lifespan, particularly in relation to DNA sequences called telomeres. Shortened telomere length may be associated with reduced life expectancy and increased morbidity. A recent six-year study published in Scientific Reports involving more than 1,900 participants concluded that drinking green tea appears to reduce the likelihood of telomere shortening compared with drinking coffee and soft drinks [5] Sohn I, Shin C. Baik I Association of green tea, coffee, and soft drink consumption with longitudinal changes in leukocyte telomere length. Scientific reports. 2023;13:492. .
In terms of specific anti-cancer properties, Smith says green tea may reduce the risk of skin cancer and premature skin aging. A 2018 review published in the journal Photodermatology, Photoimmunology and Photomedicine suggests that topical application of tea polyphenols, particularly ECGC, may help prevent UV rays from penetrating the skin and causing oxidative stress, potentially reducing the risk of skin cancer [6] Sharma P ., Montes de Oca M.C., Alkeswani A.R. etc. Tea polyphenols can prevent skin cancer caused by ultraviolet B. Photodermatology, photoimmunology and photomedicine. 2018;34(1):50–59. . However, more human clinical trials are needed to confirm these effects.
According to a 2017 review, drinking green tea may have cognitive benefits, including reducing anxiety and improving memory and cognition. Another 2017 review concluded that caffeine and L-theanine in green tea appear to improve concentration and reduce distractibility [7] Dietz S, Dekker M. Effects of green tea phytochemicals on mood and cognition. Modern drug design. 2017;23(19):2876–2905. .
“More research is needed to determine the full extent and mechanisms of the neuroprotective effects of green tea compounds in humans,” warns Smith.
“It is important to note that most side effects are associated with excessive consumption (of green tea) or the use of green tea supplements, which may contain much higher concentrations of bioactive compounds than brewed tea,” Smith said. “For most people, drinking green tea in moderation is generally safe. However, if a person has certain health problems or is taking medications, it is always recommended to consult a doctor before making major changes to their green tea consumption.”
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While both black and green tea contain caffeine, black tea typically has a higher caffeine content, depending on processing and brewing methods, so it is more likely to increase alertness, Smith said.
In a 2021 study published in the journal African Health Sciences, researchers concluded that drinking one to four cups of black tea per day, with caffeine intake ranging from 450 to 600 milligrams, may help prevent depression. Effects of black tea and caffeine consumption on the risk of depression among black tea consumers. African Health Sciences. 2021;21(2):858–865. .
Some evidence suggests that black tea may slightly improve bone health and help raise blood pressure in people who have low blood pressure after eating. Additionally, the polyphenols and flavonoids in black tea may help reduce oxidative stress, inflammation and carcinogenesis, Dr. Tiutan said.
A 2022 study of nearly 500,000 men and women aged 40 to 69 found a moderate association between drinking two or more cups of black tea per day and a lower risk of death compared to non-tea drinkers. Paul [9] Inoue – Choi M, Ramirez Y, Cornelis MC, et al. Tea consumption and all-cause and cause-specific mortality in the UK Biobank. Annals of Internal Medicine. 2022;175:1201–1211. .
“This is the largest study of its kind to date, with a follow-up period of more than ten years and good results in terms of mortality reduction,” Dr. Tiutan said. However, the study’s findings contradict mixed results from past studies, he added. Additionally, Dr. Tiutan noted that the study participants were primarily white, so further research is needed to fully understand the effect of black tea on mortality in the general population.
According to the National Library of Medicine of the National Institutes of Health, moderate amounts of black tea (no more than four cups per day) are safe for most people, but pregnant and breastfeeding women should not drink more than three cups per day. Consuming more than recommended may cause headaches and irregular heartbeat.
People with certain medical conditions may experience worsening symptoms if they drink black tea. The US National Library of Medicine also states that people with the following conditions should drink black tea with caution:
Dr. Tiutan recommends talking with your doctor about how black tea may interact with certain medications, including antibiotics and medications for depression, asthma and epilepsy, as well as some supplements.
Both types of tea have potential health benefits, although green tea is slightly superior to black tea in terms of research-based findings. Personal factors can help you decide whether to choose green or black tea.
Green tea needs to be brewed more thoroughly in slightly cooler water to avoid a bitter taste, so it may be more suitable for people who prefer a thorough brewing process. According to Smith, black tea is easier to brew and can withstand higher temperatures and different steeping times.
Taste preferences also determine which tea is suitable for a particular person. Green tea typically has a fresh, herbaceous or vegetal taste. According to Smith, depending on the origin and processing, its flavor can range from sweet and nutty to salty and slightly astringent. Black tea has a richer, more pronounced flavor that ranges from malty and sweet to fruity and even slightly smoky.
Smith suggests that people sensitive to caffeine may prefer green tea, which typically has a lower caffeine content than black tea and can provide a mild caffeine hit without being overly stimulating. She adds that people who want to switch from coffee to tea may find that the higher caffeine content of black tea makes the transition less dramatic.
For those seeking relaxation, Smith says green tea contains L-theanine, an amino acid that promotes relaxation and works synergistically with caffeine to improve cognitive function without causing jitters. Black tea also contains L-theanine, but in smaller quantities.
No matter what type of tea you choose, you’ll likely reap some health benefits. But also keep in mind that teas can vary widely not only in tea brand, but also in antioxidant content, tea freshness and steeping time, so it’s difficult to generalize about tea’s benefits, says Dr. Tiutan. He noted that one study on the antioxidant properties of black tea tested 51 types of black tea.
“It really depends on the type of black tea and the type and arrangement of the tea leaves, which can change the amount of these compounds contained [in the tea],” Tutan said. “So they both have different levels of antioxidant activity. It’s hard to say that black tea has unique benefits over green tea because the relationship between the two is so variable. If there is a difference at all, it is probably small.”
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Virginia Pelley lives in Tampa, Florida and is a former women’s magazine editor who has written about health and fitness for Men’s Journal, Cosmopolitan Magazine, Chicago Tribune, WashingtonPost.com, Greatist and Beachbody. She has also written for MarieClaire.com, TheAtlantic.com, Glamor magazine, Fatherly and VICE. She is a big fan of fitness videos on YouTube and also enjoys surfing and exploring the natural springs in the state where she lives.
Keri Gans is a registered dietitian, certified yoga teacher, spokesperson, speaker, author, and author of The Small Change Diet. The Keri Report is her own bi-monthly podcast and newsletter that helps convey her no-nonsense yet fun approach to healthy living. Hans is a popular nutrition expert who has given thousands of interviews around the world. Her experience has been featured in popular media outlets such as Forbes, Shape, Prevention, Women’s Health, The Dr. Oz Show, Good Morning America and FOX Business. She lives in New York City with her husband Bart and four-legged son Cooper, an animal lover, Netflix aficionado, and martini aficionado.