▎ WuXi AppTec content team editor
Tea, including white tea, green tea, yellow tea, black tea, black tea and oolong tea, is the second most common drink in the world after water, and it is also one of the "seven things to open the door" (chai rice oil salt sauce vinegar tea) in Chinese.
Chinese tea drinking can be described as a long history, the Tang Dynasty Lu Yu's "Tea Classic" is the earliest, most complete and most comprehensive introduction to tea in China and even the world, and is known as the tea encyclopedia.
In the past, drinking tea might have been just a habit. Now, as more research unfolds, scientists have found that drinking tea may be an integral part of a healthy lifestyle that can boost health in many ways, including improving immune and cognitive function and reducing the risk of cancer and cardiometabolic diseases (CMD).
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What substances are contained in tea?
Tea contains tea polyphenols, caffeine, theanine and other substances.
Tea polyphenols are most abundant in tea, including flavonoids, catechins and so on.
Flavonoids are naturally occurring compounds with antioxidant properties. Flavonoids help neutralize free radicals, which can damage elements in the body, such as genetic material and lipids, and lead to chronic disease.
The most important of the catechins is EGCG (epigallocatechin gallate), and several studies have shown that EGCG can play an active role in anti-cancer, antioxidant and regulation of glycolipid metabolism.
Caffeine is a central nervous system stimulant that has a refreshing effect; theanine can make tea fresh and resistant to fatigue for a longer time.
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Drink tea with immune function
Drinking tea may help strengthen the immune system function, increase the body's resistance to disease, and not only help reduce the risk of disease caused by infection, but may also reduce the severity of the disease.
A number of studies have shown that green tea and catechins can reduce the ability of pathogens to infect the host, helping the host's immune system to function better, thereby fighting the infection of pathogens.
In addition, studies have shown that green tea and catechins can improve autoimmune diseases by promoting self-tolerance, inhibiting autoantigen-induced inflammatory attacks, and enhancing tissue repair.
Drinking tea with cognitive function
There is strong evidence that L-theanine and other substances contained in tea have a certain decompression effect. Regular tea drinking, including herbal teas such as chamomile and peppermint, as well as green tea, can play a role in relieving anxiety, producing a calming effect, helping to improve concentration and increase alertness.
Drinking tea also helps prevent cognitive decline and reduce the risk of dementia. Since there are currently no effective treatments for dementia, it is crucial to prevent the occurrence of dementia. It is estimated that 40%-50% of dementia worldwide can be prevented through lifestyle changes.
A growing body of research has shown that drinking tea is associated with a reduced risk of dementias such as vascular dementia and Alzheimer's disease.
A large study published in PLOS Medicine that included 365682 participants found that drinking 0.5-1 cups, 2-3 cups, and ≥ 4 cups of tea per day was associated with an 8%, 8%, and 11% reduction in dementia risk, respectively, compared with participants who did not drink tea.
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Drink tea with cancer
Laboratory studies have found that flavonoids in tea may play a role in preventing cancer through antioxidant, anti-angiogenesis, anti-inflammatory mechanisms and changes in the intestinal flora, etc., to protect DNA from cancer cell damage, or to intervene in the growth and spread of cancer cells.
Studies have shown that drinking tea may be associated with a reduced risk of cancers such as colorectal, prostate, ovarian, biliary, breast, skin, endometrial, liver, and oral cancers. A U.S. study of 566 participants found that people who drank black tea had a 40 percent lower risk of skin squamous cell carcinoma compared to people who didn't drink black tea.
In addition, there are studies that show that drinking tea is associated with better survival of cancer patients.
A study of 8,900 female participants with stage I-III breast cancer, published in the British Journal of Cancer, showed that drinking 2-3 cups of tea per day and > 3 cups of tea per day was associated with a 15% and 26% lower risk of all-cause death and a 17% and 20% lower risk of breast cancer-specific death compared to women who did not drink tea.
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Drink tea with cardiometabolic diseases
Cardiometabolic diseases, such as cardiovascular disease and diabetes, are the leading causes of death worldwide. Multiple studies have shown that drinking tea may help reduce the risk of developing and progressing cardiometabolic diseases in adults.
A study published in the European Journal of Preventive Cardiology by a team of academicians Gu Dongfeng of the Chinese Academy of Medical Sciences and Peking Union Medical College showed that drinking tea at least 3 times a week helps prolong life and reduce the risk of atherosclerotic cardiovascular disease and all-cause death.
Compared with people who never drank tea or did not have a tea drinking habit, the risk of atherosclerotic cardiovascular disease onset and death was reduced by 20% and 22%, respectively; the risk of all-cause death was reduced by 15%.
There are also studies that have shown that drinking 1 cup of tea a day is associated with a 2% and 4% lower risk of cardiovascular disease and death, a 4% lower risk of stroke, and a 1.5% lower risk of all-cause death, respectively.
A large retrospective cohort study in Japan found that drinking 6 cups of green tea a day was associated with a 33% lower risk of type 2 diabetes.
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Tea drinking precautions
Although there are growing studies finding that drinking tea is good for health. But there are also some things to pay attention to when drinking tea, otherwise, it is not only not beneficial to health, but also may be harmful.
First of all, do not drink too hot tea. Because the water temperature is too high, it is easy to burn the mouth and the mucous membranes of the esophagus, which will increase the risk of oral cancer and esophageal cancer.
Second, pay attention to the concentration of tea drinking. In particular, strong tea is easy to stimulate the stomach and accelerate the secretion of stomach acid, which is easy to damage the stomach.
Third, do not add too much sugar or other ingredients when drinking tea. Excessive intake of added sugars can have harmful effects on health and increase the risk of many diseases such as cancer.
Fourth, pay attention to the time to drink tea, do not drink tea on an empty stomach, especially people with chronic gastritis and other stomach diseases. Drinking tea on an empty stomach can cause discomfort, which is mainly related to the caffeine in tea. Excessive intake of caffeine can make people feel palpitations, dizziness, weakness in hands and feet, trance, etc.
Fifth, don't drink tea before going to bed. Drinking tea before bedtime can make it difficult to fall asleep, affect sleep and the next day's mental state, and people with neurasthenia or insomnia should pay special attention.
Sixth, do not take medicine with tea. The substances contained in tea may react with drugs, hinder absorption, affect efficacy, and even change medicinal properties, which have harmful effects on health.
Seventh, do not drink overnight tea. Overnight tea is susceptible to microbial contamination due to its long time, and the complex components of the tea are also prone to change, which may cause gastrointestinal diseases after drinking.
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brief summary
All in all, drinking tea can be an integral part of a healthy lifestyle. The Dietary Guidelines for Chinese Residents (2022 Edition) recommend that adults drink 1500 ml-1700 ml per day instead of sugary drinks with water or tea.
At the same time, it should also be noted that although drinking tea is beneficial to health, drinking tea cannot be used as the main method of promoting health, but should adopt a variety of healthy lifestyles, including a balanced diet, enhanced exercise, no smoking, no drinking, and guaranteed sleep, etc. Only a multi-pronged approach can better improve the overall health level through lifestyle and reduce the risk of disease and death.
Resources
[1] Yuan Zhang, et al.,(2021). Consumption of coffee and tea and risk of developing stroke, dementia, and poststroke dementia: A cohort study in the UK Biobank. PLOS Medicine, DOI: https://doi.org/10.1371/journal.pmed.1003830.
[2] Maryam S. Farvid, et al.,(2021). Post-diagnostic coffee and tea consumption and breast cancer survival. British Journal of Cancer, DOI: 10.1038/s41416-021-01277-1.
[3] Xinyan Wang, et al.,(2020). Tea consumption and the risk of atherosclerotic cardiovascular disease and all-cause mortality: The China-PAR project. European Journal of Preventive Cardiology, DOI：https://doi.org/10.1177/2047487319894685.
[4] Klaus W.Lange, et al.,(2022). Tea and depression. Food Science and Human Wellness, DOI：https://doi.org/10.1016/j.fshw.2021.12.032.
[5] Harold N.Graham, et al.,(1992). Green tea composition, consumption, and polyphenol chemistry. Preventive Medicine, DOI：https://doi.org/10.1016/0091-7435(92)90041-F.
[6] Klaus W.Lange, et al.,(2022). Tea in cardiovascular health and disease: a critical appraisal of the evidence. Food Science and Human Wellness, DOI：https://doi.org/10.1016/j.fshw.2021.12.034.
[7] From immune function and cognition to cardiovascular health and cancer prevention – health benefits of tea revealed by researchers from across the globe. Retrieved May 4 ,2022,from https://www.eurekalert.org/news-releases/950788
[8] Tea and cancer prevention 101. Retrieved May 4 ,2022,from https://www.mdanderson.org/cancerwise/tea-and-cancer-prevention-101-does-tea-prevent-cancer.h00-159460056.html
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