Is Overnight Tea Harmful? Debunking the Myths and Facts

People often say, "Overnight tea is as poisonous as a snake." Many people choose to pour out the tea that was brewed the day before and not consumed. Is overnight tea really that harmful?

1. Overnight tea is not spoiled and does not affect consumption compared to freshly brewed tea

To prove whether overnight tea is harmful to the human body, some people conducted experiments using three commonly consumed teas: Longjing tea, Pu'er tea, and chrysanthemum tea. On the first day at 9 am, they brewed the teas and let them sit. At 9 pm, they brewed another three cups of tea and left them overnight. On the second day at 9 am, they brewed fresh tea again. By this time, the tea brewed at 9 am the previous day had been sitting for 24 hours, and the tea brewed at 9 pm the previous day had been sitting for over 12 hours. After being left for a long time, how different are these overnight teas compared to fresh tea? National senior tea expert Lou Guozhu evaluated the taste of the teas and compared them in terms of flavor. He concluded that whether the tea had been left for 12 or 24 hours, the overnight tea did not spoil.

Lou Guozhu explained that although overnight tea is brewed for a longer period of time, it still retains the original taste of the tea, and in some cases, Pu'er tea, which emphasizes flavor and mellowness, may even taste better after being left overnight.

2. Nitrite content in overnight tea is lower than the national drinking water hygiene standard

The brewed samples were sent to the Beijing Nutrition Research Institute to test the nitrite content in the tea. Currently, there is no national standard for nitrite content in tea, but the national drinking water hygiene standard specifies that the nitrite content in drinking water should be less than 1mg/L. The test results showed that both Pu'er tea and chrysanthemum tea, whether freshly brewed, left for 12 or 24 hours, had nitrite levels below 0.2mg/L. As for Longjing tea, the freshly brewed tea also had nitrite levels below 0.2mg/L, but the nitrite levels in the tea left for 12 and 24 hours were 0.25mg/L and 0.26mg/L, slightly higher than the others but still below 1mg/L. Therefore, the tested overnight teas had nitrite levels lower than the national drinking water hygiene standard, and even the highest nitrite content in Longjing tea accounted for only about 1/4 of the national standard.

Lou Guozhu explained that the nitrite content in tea left overnight is even lower than that in a cup of boiled water. This is because tea leaves contain a component called tea polyphenols, which inhibits the formation of nitrites. Therefore, tea is a natural antioxidant.

3. Pay attention to tea drinking taboos

The safety of overnight tea has been confirmed, but there are still some precautions to consider for a healthy tea drinking experience:

1. Do not drink hot tea: Tea that is too hot can cause irritation to the digestive tract. Prolonged consumption of hot tea can lead to damage to the stomach lining and the development of stomach diseases. The temperature of the tea should be below 56°C.

2. Do not drink tea on an empty stomach or before meals: In ancient China, there was a saying "do not drink tea on an empty stomach." Drinking tea on an empty stomach or before meals can dilute saliva, making food tasteless and reducing the absorption of protein by the digestive organs.

3. Do not drink tea immediately after meals: Tea contains tannic acid, which can coagulate with proteins and iron in food, affecting the digestion and absorption of protein and iron in the body.

4. Do not take medicine with tea: Tea leaves contain a large amount of tannins, which can be broken down into tannic acid. Tannic acid can combine with many drugs, forming precipitates that hinder absorption and affect the efficacy of the medication. This is why there is a saying that "tea water neutralizes medicine".

Drinking overnight tea is not as scary as it seems, but it is important to pay attention to when and how to drink tea for the best health benefits.