Tea is the most consumed drink in the world, after water. Although many health benefits have been attributed to tea since the beginning of its history, scientific research on tea and its components has been ongoing for some 30 years.
The first record that tea was not only a drink that was worth enjoying for its flavor and aroma is from the year 300 BC. Incredibly, already at that time a doctor ( Hua Tuo ), conducted a well-organized study on his patients and described how drinking tea every day improved the health of his patients or seemed to prevent certain diseases.
In the 21st century, some 2,000 relevant scientific studies have already been carried out on the effect of tea on health. In the book Herbal Medicine: Biomolecular and Clinical Aspects, used as a textbook at the University of Florida, the authors have attempted to compile all approved and published scientific studies showing the health effects of tea as well as the quantity and type of tea that is recommended to drink.
Is it the tea or is it the culture?
A problem that frequently arises in studies is that tea consumption is associated with other cultural variables. For example, much more tea is drunk in the East than in the West, so one might expect people to be healthier in Asia. And in fact it is, but there are other factors that affect it, for example, the lower consumption of fatty beef or the higher consumption of vegetable proteins.
On the other hand, around the world, people who drink tea instead of coffee tend to take better care of their bodies, not drink alcohol or exercise. And people who prefer coffee usually smoke.
So in the end, it’s hard to tell if they are healthier from drinking tea or from the rest of their habits.
So the authors of the aforementioned book have concentrated on studies that speak of the benefit of the two most important components of tea: polyphenols ( including catechins) and caffeine. These two types of compounds are present in variable amounts depending on the type of tea . Usually scientific studies are based on the use of green, black , oolong and white tea as a daily drink, for a moderate or long time, at least 1 year.
Effects of drinking tea every day
Considering only these 2 chemical groups, these are some of the effects of tea on the human body:
– Influence on cardiovascular health: This is the most studied and proven effect. Almost all studies have proven that people who consume moderate or high amounts of green or black tea (or flavonoids from all dietary sources) have a reduced risk of cardiovascular disease and, especially, cerebrovascular accident (CVA).
This decreased risk was also seen in people taking catechins in dietary supplement pills and is accompanied by decreased LDL (“bad”) cholesterol, blood pressure, and the formation of circulating blood clots.
– Prevention or inhibition of cancer: In laboratory studies, green tea extracts and tea polyphenols administered separately have been shown to inhibit a wide variety of cancers; black tea has been less studied because it has fewer polyphenols.
There are many theories as to how these compounds may have anti-cancer effects, for example by inducing cell suicide in cancer cells and by inhibiting insulin growth factor (a protein involved in cell proliferation).
But above all, the effects are observed with the naked eye when studying cancer case statistics and how they decrease in areas where green tea consumption is higher due to cultural issues. Clinical trials, that is, experiments with cancer patients treated with polyphenols, are still few, but they are being done in prostate cancer, combining green tea with radiation.
– Diabetes: Most research has linked tea or compounds or catechins with improved blood sugar control or reduced risk of type 2 diabetes.
– Weight loss: the most relevant study was on the statistics of the huge US Health and Nutrition Survey between the years 2003 and 2006. There was a clear inverse relationship between the waist size of the respondents and the amount of tea green they drank The mechanism of action seems related to the diuretic and fat-burning effect of caffeine.
– Mental health: studies in humans have been limited almost exclusively to people over 60 years of age, showing that those who had drunk any type of tea in the last 10 years had less cognitive impairment. In laboratory animals, the effect of caffeine in increasing learning and alertness has been tested on many occasions. Also an amino acid called theanine present in tea improves concentration.
– Parkinson’s disease: A 2008 study shows that people who drank more black tea, but not green tea, had a much lower risk of Parkinson’s disease than non-drinkers.
– Bone health: Laboratory studies show that tea polyphenols have beneficial effects on factors that affect bone mass and bone strength, and therefore may help protect against osteoporosis. Bones can also benefit from fluoride in tea. Almost all of these studies were conducted on postmenopausal women who had taken green tea every day for several years.
– Does it affect DNA? : Very recently, in 2017, a study was carried out in Europe on 3000 people in the area of epigenetics . This part of genetics studies how and why some genes that we carry in our DNA are never expressed or activated and others do, and why this is variable from one person to another.
The activation of a gene can result in the appearance of a disease or in the protection against one of them. Genes are expressed by chemical changes that occur around them and it was seen that in the women studied who consumed tea there were genetic changes in 28 areas of DNA, precisely those related to growth and cancer prevention.
This would be precisely the reason why tea has been observed to prevent cancer as we described in a previous point. Interestingly, these genetic changes were not observed in men or in people who drank coffee, so they would be associated with tea consumption.
The benefits of drinking tea regularly have been described for centuries, and these that we have mentioned are only a summary of them.