The Therapeutic Effects of Tea on Human Diseases (from China Tea Book)

The development of modern society and advancements in science and technology have significantly extended human lifespan. However, with industrialization leading to environmental pollution and the continuous introduction of synthetic compounds into the human body, many diseases pose significant threats to human health. The incidence of many common diseases among humans, such as cancer, cardiovascular diseases, and diabetes, has shown a clear increasing trend. Medical research before the 1980s aimed to control these diseases primarily through synthetic chemical drugs. However, further research revealed that utilizing food to regulate human physiological functions to control diseases is fundamental and the root solution. In addition to its nutritional and taste characteristics, food is more importantly explored for its physiological regulatory functions on the human body. Numerous research findings indicate that tea is a beneficial functional food. The medicinal efficacy of tea has been recognized for over 2000 years, with legends like "Shennong tasted hundreds of herbs, encountering seventy-two toxins in a day, but was relieved by tea" dating back to ancient times. Chen Cangqi, a famous medical practitioner in the Tang Dynasty of China, wrote in his book "Compendium of Materia Medica": "Various medicines are for various diseases, but tea is for all ailments." Although this statement may be exaggerated, it at least indicates that tea indeed has various pharmacological effects. Traditional Chinese medicine has many prescriptions for using tea to treat illnesses. According to Professor Lin Qianliang's records, tea has at least 61 health benefits and more than 20 medicinal effects. Since the late 1980s, continuous in-depth research and participation in medical research have led to a better understanding of the effective components and pharmacological effects of tea.
1. Medicinal Components of Tea
Currently, it has been confirmed that the components of tea closely related to human health mainly include the following categories.
(1) Polyphenolic Compounds
Tea polyphenols are a general term for acidic substances in tea. They mainly consist of catechins, flavonoids, and phenolic acids, with catechin compounds having the highest content, accounting for about 70% of total tea polyphenols. Catechin compounds mainly include epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG). These are the main active components of tea's medicinal effects. It has been proven that they have various effects such as preventing atherosclerosis, lowering blood lipids, anti-inflammatory, antibacterial, radiation protection, and anticancer.
(2) Caffeine
Caffeine is a biological alkaloid in tea, with a relatively high content, generally ranging from 2% to 4%. A cup of 150 milliliters of tea contains about 40 milligrams of caffeine. Caffeine is a central nervous system stimulant, thus having a refreshing effect. Since caffeine in tea is often in a complexed state with tea polyphenols, its physiological functions differ from free caffeine. The conclusion of a comprehensive report on the safety assessment of caffeine is that, at normal drinking doses for humans, caffeine has no teratogenic, carcinogenic, or mutagenic effects.
(3) Amino Acids
Amino acids in tea account for about 2% to 5% of the tea's weight, including 25 types, among which the content of theanine is the highest, accounting for over 50% of the total amino acids. The quantity of amino acids is closely related to tea, especially green tea. Amino acids are essential nutrients for the human body, with some amino acids closely related to human health. For example, glutamic acid can lower blood pressure and treat hepatic coma; methionine can regulate fat metabolism; theanine has effects such as relieving fatigue, relaxing nerves, reducing blood pressure, enhancing immunity, and synergistically combating cancer with tea polyphenols.
(4) Mineral Elements
Tea contains various mineral elements such as phosphorus, potassium, calcium, magnesium, manganese, aluminum, sulfur, etc. Most of these mineral elements are necessary and beneficial for human health. Tea has a high fluoride content, averaging 100-200 milligrams per kilogram, much higher than other plants. Fluoride has obvious effects in preventing dental caries and treating osteoporosis in the elderly. In some areas, tea contains high selenium levels, with the highest selenium content reaching 3-4 milligrams per kilogram in tea from Enshi, Hubei, and Ziyang, Shaanxi, China. Selenium has the effects of enhancing immunity and anticancer. Its deficiency can cause certain local diseases, such as Keshan disease.
(5) Vitamins
Tea contains abundant vitamins. The content of B vitamins in tea generally ranges from 100 to 150 milligrams per kilogram of tea. The content of vitamin B in tea is higher than that in vegetables. Vitamin B can maintain the normal functions of the nervous, cardiovascular, and digestive systems. Tea has a high content of vitamin C, with the content in high-grade green tea reaching up to 0.5%. Vitamin C can prevent and treat scurvy, increase the body's resistance, and promote wound healing. The content of vitamin E (tocopherol) in tea is about 300 to 800 milligrams per kilogram of dry tea leaves. Vitamin E is an antioxidant with anti-aging effects. The content of vitamin K in tea is about 300 to 500 international units per gram of tea, so drinking 5 cups of tea a day can meet the body's needs. Vitamin K can promote the liver's synthesis of coagulation factors.
(6) Others
In addition to these main components, tea also contains some minor active components. Although their content is not high, they have unique medicinal effects. For example, polysaccharides in tea have the effects of radiation protection and increasing the number of white blood cells; the complexes of several polysaccharides in tea and diphenylamine in tea lipid components have the effect of lowering blood sugar; γ-aminobutyric acid formed by tea under anaerobic conditions has the effect of lowering blood pressure.

(Source: China Tea Book. Author, Mr. Chen Zongmao)