Is Overnight Tea Harmful? Debunking the Myth and Unveiling the Truth

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 tea and discard the tea brewed the day before. Some people explain that "tea left overnight will spoil and produce a large amount of nitrite, which is harmful to the human body." Is overnight tea really harmful? Or have we fallen into a misconception about drinking tea?

Overnight tea vs freshly brewed tea: No deterioration and no impact on consumption

In order to prove whether overnight tea is harmful to the human body, some people conducted experiments using three types of tea commonly consumed in daily life: Longjing, Pu'er, and chrysanthemum tea. The tea was brewed at 9 am on the first day and left to stand. At 9 pm in the evening, three cups of tea were brewed again and left to stand. At 9 am on the second day, a fresh batch of tea was brewed. By this time, the tea brewed at 9 am the previous day had been left for 24 hours, and the tea brewed at 9 pm the previous day had been left for more than 12 hours. After being left for a long time, how much difference is there between these overnight teas and freshly brewed teas? Lu Guozhu, a senior tea taster, conducted a professional evaluation of the taste of the tea leaves, comparing them in terms of taste and flavor. It was determined that both the overnight tea left for 12 hours and the one left for 24 hours had not deteriorated. Lu Guozhu explained that although the overnight tea was brewed for a relatively long time, it still had the original taste of the tea. In fact, Pu'er tea values its flavor and mellow taste, so the overnight tea might even be slightly better.

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

The brewed samples were sent to the Beijing Nutrition Source Research Institute for testing the nitrite content in the tea. Currently, there are no national regulations regarding the nitrite content in tea, but the national drinking water hygiene standard requires the nitrite content in drinking water to be less than 1mg/L. The test results showed that in both Pu'er and chrysanthemum tea, whether freshly brewed, left for 12 hours, or left for 24 hours, the nitrite content was below 0.2mg/L. As for Longjing tea, the freshly brewed one also had a nitrite content below 0.2mg/L, but the ones left for 12 hours and 24 hours had nitrite contents of 0.25mg/L and 0.26mg/L, slightly higher than the others, but still below 1mg/L. Therefore, the detected nitrite content in the overnight tea was below the national drinking water hygiene standard. Lu Guozhu explained that if you compare a cup of plain boiling water and a cup of tea left overnight, the nitrite content in the tea is even lower than that in plain boiling water. This is because tea leaves contain a component called tea polyphenols, which inhibits the formation of nitrite. Therefore, tea leaves act as a natural antioxidant.

Precautions for drinking tea

The safety of overnight tea has been confirmed. But what should we pay attention to for a healthier way of drinking tea? Here are some tea drinking taboos:

Avoid drinking hot tea. Tea that is too hot can irritate the digestive tract. If you drink excessively hot tea for a long time, it may cause damage to these organs. The stomach lining is more susceptible to damage and may lead to stomach problems. The temperature of tea should be below 56°C.

Avoid drinking tea on an empty stomach or before meals. In ancient China, there was a saying, "Do not drink empty-stomach tea." Drinking tea on an empty stomach or before meals can dilute saliva, make food tasteless, and decrease the absorption of protein by the digestive organs.

Avoid drinking tea immediately after a meal. 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.

Avoid taking medication with tea. Tea leaves contain a large amount of tannins, which can be broken down into tannic acid. It can combine with many drugs and form precipitates, hindering absorption and affecting efficacy. Hence the saying, "Tea water neutralizes medication."

Drinking overnight tea is not as scary as it seems. What is important is knowing when it is the healthiest and harmless to drink tea.