Why should you not drink overnight tea?

Generally speaking, the reasons why overnight tea should not be consumed include oxidation of tea polyphenols, increased nitrite content, reduced nutritional value, pigment precipitation, and microbial growth. A detailed analysis is as follows:

1. Oxidation of Tea Polyphenols

Tea polyphenols are components of tea leaves that possess various bioactive properties, such as antioxidant and antibacterial effects. However, when exposed to air for an extended period, tea polyphenols undergo oxidation reactions with oxygen, producing oxidized products that cause discoloration of the tea and a deterioration in taste.

2. Increased Nitrite Content

Nitrates present in tea leaves can be converted into nitrites by bacteria under suitable conditions, especially in environments with high temperature and humidity. Nitrites can combine with amine compounds in the human body to form nitrosamines, which may have carcinogenic potential.

3. Reduced Nutritional Value

Some nutrients in tea, such as vitamin C and tea polyphenols, can gradually oxidize and decompose when exposed to air for prolonged periods, leading to a reduction in their content and loss of original nutritional value.

4. Pigment Precipitation

Overnight tea left standing for too long allows pigments to fully dissolve in the tea over extended steeping time, which may result in pigment precipitation. Long-term consumption of such tea may lead to tooth discoloration and affect aesthetics.

5. Microbial Growth

During storage, especially in warm and humid environments, overnight tea may become a breeding ground for bacteria and other microorganisms. These microorganisms may include pathogenic bacteria such as Escherichia coli (E. coli), which can multiply rapidly in the tea and increase the risk of food poisoning.

To maintain the safety, nutritional value, and personal health benefits of tea, it is recommended to consume it soon after brewing and avoid drinking overnight tea as much as possible.