Nitrite levels in overnight tea do not increase

Many people believe that overnight tea should not be consumed. Some conducted an experiment with Pu'er tea, chrysanthemum tea, and Longjing tea. After brewing, the teas were left for 12 and 24 hours—a period sufficient to qualify as overnight tea. Tests showed that the nitrite levels in Pu'er tea and chrysanthemum tea did not exceed the standard after either 12 or 24 hours, remaining below 0.2 mg/L. The nitrite level in Longjing tea was slightly higher, reaching about 0.26 mg/L, but still well below the national standard of 1 mg/L.

In fact, the nitrite content of plain boiled water left for 24 hours is higher than that of tea. This is because tea contains antioxidants such as tea polyphenols, which help reduce nitrite formation, so there is no need for concern.

No need to worry about darkening tea color

Having addressed the nitrite issue, some may ask why the color of overnight tea changes. When tea is freshly brewed, its color is usually yellow-green because theaflavins, an antioxidant that helps prevent cardiovascular and cerebrovascular diseases, are released. The color of overnight tea shifts from yellow-green to yellow-red as theaflavins transform into thearubigins. Despite this color change, the antioxidant capacity remains unchanged, so there is no reason to be concerned.

Dilute overnight tea with hot water

Overnight tea is usually made the night before. Drinking it on an empty stomach in the morning may irritate those with weak gastrointestinal function. It is therefore recommended to add some hot water to dilute it.

Based on the three points above, you can drink overnight tea without any lingering doubts.