So-called "over tea and after meals" and "firewood, rice, oil, salt, sauce, vinegar, and tea" — tea has always been an essential part of daily life. Tea can cultivate character and improve mood; tea can boost energy and dispel fatigue; tea can also speed up metabolism and help prevent obesity and stones. However, in everyday tea drinking, there are still some aspects we often overlook that deserve attention.

[Myth: The "aftertaste" of tea is due to bitterness giving way to sweetness]

Rumor: The "aftertaste" of tea is because bitter substances numb our bitter taste receptors, which in turn promotes a sweet aftertaste.

Truth: The "aftertaste" of tea is because it itself contains sugars or amino acids, only that the tongue is more sensitive to bitterness, tasting the bitter substances first before tasting the sweetness.

Evidence: "Bitterness ends, sweetness comes" is a well-known idiom. It seems sweetness arises from bitterness, but the truth may not be so.

Generally, when we drink tea, the first sensation is usually bitterness, due to the presence of substances like theophylline and tea polyphenols. So, do these bitter substances numb our bitter taste receptors, thus making us perceive sweetness? (This is our common understanding.) Wait! Try taking a bitter pill like quinine, and you'll find only bitterness remains in your mouth.

In fact, tea itself contains sweet substances, namely sugars and amino acids. However, our tongue is more sensitive to bitterness; we first taste the theophylline and tea polyphenols, and only later perceive the sweetness. This is the true source of the aftertaste.

Additionally, drinking tea also has a saliva-inducing effect, simply put, increasing saliva flow.

Besides bitterness, tea polyphenols also have a special astringency. In human saliva, a group of proline-rich proteins (PRPs) has been found. These proteins provide moisture and lubrication, but tea polyphenols can alter their properties, forming complexes that cause the oral epithelium to perceive a loss of lubrication, i.e., astringency.

This astringency, like sourness, can accelerate saliva flow, giving us the sensation of "producing saliva."

[Truth: Using tea to take medicine may reduce efficacy]

Rumor: Do not take medicine with tea, as it can neutralize the drug's effect and make it ineffective for treating illness.

Truth: Polyphenols and tannins in tea may form precipitates with components in medications, reducing efficacy. Medicines should be taken with warm boiled water.

Evidence: In most cases, taking medicine with tea is not recommended, especially Western medicines containing iron agents such as ferrous sulfate, ferrous carbonate, ferric citrate, and aluminum agents like aluminum hydroxide, where metal ions can combine with tea polyphenols in the tea to form precipitates, thereby reducing or losing efficacy.

Some Chinese herbal medicines, such as Ephedra, Coptis, Uncaria, Scutellaria, Ginseng, and related alkaloid preparations, as well as medications like Atropine and Aspirin, are generally not suitable to be taken with tea, otherwise the effective ingredients like ephedrine can be precipitated by tannins in tea, losing efficacy.

When taking enzyme preparations, such as protease and amylase, tea should not be consumed, as polyphenols in tea can bind to enzymes, reducing their activity. Additionally, tea contains caffeine (also known as "caffeine alkaloid"), which has a stimulating effect. Therefore, when taking sedatives, hypnotics, or cough suppressants, tea should also not be used to take medicine, to avoid conflict and reduced efficacy.

[Myth: Drinking overnight tea can cause cancer]

Rumor: Tea is a very healthy beverage. But people often say: "Overnight tea is as poisonous as a snake," so many people choose to drink freshly brewed new tea and discard tea brewed the previous day. Recently, a netizen posted: "Tea left for a long time can go rancid and produce large amounts of nitrite, causing harm to the human body, so overnight tea cannot be drunk." Is overnight tea really harmful?

Truth: The main change in overnight tea is that tea polyphenols are oxidized to form more pigments, making the tea soup appear darker in color. Meanwhile, some flavor compounds, such as amino acids, are oxidized, losing their freshness. If there is no external microbial contamination, it is safe.

Evidence: The CCTV program "Is It True?" investigated this claim and concluded that overnight tea is safe to drink.

First, experiments were conducted to verify the truth. The CCTV reporter selected three common teas: Longjing, Pu'er, and Chrysanthemum tea. At 9 a.m. on the first day of the experiment, the reporter brewed these three teas and left them to sit. At 9 p.m. that evening, the reporter brewed three more cups of tea and set them aside. At 9 a.m. the next day, the reporter brewed another three cups of fresh tea. At this point, the tea brewed at 9 a.m. the previous day had been sitting for 24 hours, and the tea brewed at 9 p.m. the previous evening had been sitting for over 12 hours. After such prolonged storage, how different were these overnight teas from the freshly brewed tea?

The truth team invited national senior tea taster Lou Guozhu to professionally evaluate the taste of these overnight teas. Mr. Lou compared taste and flavor, concluding that neither the 12-hour nor the 24-hour overnight teas had spoiled. "Although they have been steeped for a long time, they still retain the flavor that the tea should originally have. Pu'er emphasizes its aged aroma and mellow taste; overnight tea might even be better."

National senior tea taster Lou Guozhu stated: "Compared to the same cup of plain water and a cup of tea left overnight, the nitrite content in the tea is even lower than that in plain water. This is because tea contains a significant component called tea polyphenols, along with some vitamins. These act as natural antioxidants that hinder the formation of nitrite."

It has been confirmed that overnight tea is safe to drink. Regarding how to drink tea healthily, experts suggest: "Drinking tea on an empty stomach can be quite irritating to the stomach, so avoid drinking cold overnight tea on an empty stomach. Adding a little warm water or warming the tea water can still be beneficial to health."