Tea is a very healthy beverage. However, it's often said that "overnight tea is as poisonous as a snake," so many people choose to drink freshly brewed tea and discard the tea brewed the previous day. Recently, a netizen posted that "tea left for a long time will spoil and produce a large amount of nitrite, which can be harmful to the human body, so overnight tea should not be drunk." Is overnight tea really harmful to the human body? Experts investigated this claim and concluded that overnight tea is safe and drinkable.
Overnight tea is not spoiled and does not affect its drinkability compared to freshly brewed tea.
First, an experiment was conducted to verify the truth. Three commonly consumed teas were selected: Longjing, Pu'er, and chrysanthemum tea. On the first day of the experiment, at 9:00 AM, the reporter brewed all three teas and left the tea to steep. That evening at 9:00 PM, the reporter brewed three more cups of tea and left them to steep. The next morning at 9:00 AM, the reporter brewed three more cups of tea. At this point, the tea brewed at 9:00 AM the previous day had been steeped for 24 hours, and the tea brewed at 9:00 PM the previous evening had been steeped for over 12 hours. After such a long period of steeping, how different was this overnight tea from freshly brewed tea?
The Truth Team invited a senior national tea taster to professionally evaluate the taste of these overnight teas. Mr. Lou compared the taste and flavor, concluding that neither the teas left for 12 hours nor 24 hours had spoiled. "Although they have been steeped for a long time, they still retain the original taste of the tea. Pu'er tea emphasizes flavor and mellowness, and overnight tea might even be better." Although the taste of the overnight tea did not affect its edibility, the Truth Team still needed to test the nitrite content in the overnight tea to verify whether it was harmful to the human body.
The nitrite content of overnight tea was lower than the national drinking water hygiene standards.
The reporter sent a sample of the brewed tea to the Nutrition Source Research Institute for testing of its nitrite content. The reporter learned that there are no national standards for nitrite content in tea water. However, the national hygiene standards for drinking water stipulate that the nitrite content in drinking water should be less than or equal to 1 mg/L.
A week later, the reporter obtained the test data. The data showed that in both Pu'er and chrysanthemum tea, whether freshly brewed or left for 12 and 24 hours, the nitrite content was below 0.2 mg/L. Freshly brewed Longjing tea also had a nitrite content below 0.2 mg/L. However, the nitrite content in Longjing tea left for 12 and 24 hours was 0.25 mg/L and 0.26 mg/L respectively, slightly higher than the others, but still below 1 mg/L. Therefore, it appears that the nitrite content in the overnight tea tested by the investigation team was below the national drinking water standards. Even Longjing tea, which had the highest content, only met about one-quarter of the national drinking water standards.
A senior national tea expert stated, "If you leave a glass of plain water and a glass of tea overnight, the tea will contain less nitrite than the water. This is because tea contains a relatively high amount of polyphenols and some vitamins, which help inhibit the formation of nitrite and act as natural antioxidants."
It has been proven that overnight tea is safe and drinkable. Regarding healthier ways to drink tea, experts advise: "Drinking tea on an empty stomach can be very irritating to the stomach, so please avoid drinking overnight cold tea on an empty stomach. Adding a little warm water or warm tea to it will be beneficial to your health."
