When I was young, I only knew of two types of tea: "big bowl tea" and "Biluochun" tea. Later, I learned about tea because of studying traditional Chinese medicine and discovering that tea is also a type of medicine. For example, the Chuanxiong tea blend is recorded in the "Essentials of Materia Medica": "Tea leaves have a bitter and sweet taste. They enter the Hand and Foot Shaoyin, Taiyin, and Jueyin meridians. They are effective in clearing the heart and lungs, purging the intestines and stomach. When combined with chamomile, it can treat headaches; when combined with ginger, it can relieve water retention and stimulate the bladder and kidney meridians when consumed after drinking alcohol." However, tea is ultimately cold in nature, and since my body constitution is weak and cold in the spleen and stomach, I remember drinking Pu-erh tea once and having to go to the bathroom halfway through, so I rarely drink tea. But one chance encounter changed my perspective.
Recently, I went to visit a small shop near the Wudaoying Hutong next to the Beijing Yonghegong Temple. The shop owner is a good friend of mine who invited me to try Biluochun tea. This is a type of green tea, and at the time it was dinner time, so how could I dare to drink green tea on an empty stomach? So I politely declined. But my friend said, "Just take a sip, I guarantee it won't be too cold." She said that this tea comes from an 80-year-old tea tree growing on a sunny mountain in Dongting Lake. This is the first crop of early spring tea picked by hand and processed with firewood, so it is not like other green teas. Unable to resist her persuasion, I sat down and tasted the Biluochun tea. After drinking a few cups, I was surprised to find that my stomach and intestines felt slightly warm and comfortable, with no signs of diarrhea. I let out a few belches and felt quite comfortable, and even had a slight feeling of fullness. I stayed until 8pm, drinking the tea on an empty stomach, without any discomfort, and even feeling slightly full without hunger. The warm tea entered my stomach and I broke out into a light sweat, feeling very comfortable. Later, my friend gave me some Biluochun tea, and every time I drank it, I felt the same way, so it seems to be no coincidence.
This chance encounter changed my understanding of tea, especially green tea, and reminded me of an elderly person who once said that his father, who was over ninety years old, had been drinking tea his whole life and lived a long and healthy life, as did many other elderly people. At first, I thought it was due to their physical constitution, but now I see it's not entirely the case. Recently, I've been thinking carefully and have had some realizations.
Although the nature of tea is generally cool, ultimately its temperature can be influenced by two factors: first, the growth environment, whether it is in a relatively yin, cold, and humid area or a warm and sunny one. Just like the difference between grapes grown in the north of China and those grown in Xinjiang, or the difference between two types of Chinese medicinal herbs called niuxi: Sichuan niuxi promotes blood circulation, while Henan niuxi nourishes the liver and kidneys. Similarly, ginseng grown in the northeast is warm in nature, while American ginseng is cooler. These differences in nature are due to their different growing environments, including temperature, sunlight, soil, and planting methods.
Second, the processing methods are also important. Most teas need to be withered and then undergo a process called "kill-green," which involves roasting with fire. Traditional Chinese medicine believes that medicinal herbs and raw herbs that have been processed by fire have different cold, hot, warm, or cool properties. For example, raw licorice has a cold and cool nature that can clear away heat and detoxify, while roasted licorice can tonify the spleen and supplement qi. Raw rehmannia has a cool nature that can cool and activate blood, while steamed rehmannia has a slightly warm nature that can nourish the kidneys. Most herbs that have been processed by fire tend to have some warm properties, depending on the specific method of fire processing, which can even vary between using firewood or an oven.
There are many steps involved in tea processing, and many of them involve using fire, either by roasting or steaming. The tea processing method determines the warmth or coolness of the tea. I used to think that fermented teas, such as black tea and Pu-erh tea, were not cool, but that was because I didn't understand the fermentation process of tea. Tea fermentation is usually done by spreading the tea leaves flat and letting them sit at room temperature of around 25 degrees Celsius, so it's different from using fire. Therefore, to sum up, the warmth or coolness of tea depends on the environment and processing method.
In light of this, people with a cold constitution are not necessarily unable to drink green tea, while some fermented teas, such as Pu-erh tea, may not be suitable. Therefore, finding the right tea for oneself and knowing the principle of moderation is the key to health.
Author: Zhang Dong, Chief Physician of the Cardiovascular Department at Xiyuan Hospital, China Academy of Chinese Medical Sciences.
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