Can I drink overnight green tea?

Generally speaking, it is not recommended to drink green tea left overnight, and the reasons are analyzed as follows:

The nutritional components in green tea, such as polyphenols and vitamin C, will gradually oxidize and decrease over time. Tea polyphenols are important antioxidants in green tea, offering multiple health benefits including boosting immunity, but their antioxidant activity diminishes after being left overnight. At the same time, vitamin C also oxidizes significantly, leading to a reduction in the tea's nutritional value.

In addition, overnight green tea may produce harmful substances like tannic acid during storage. Tannic acid can combine with oxalic acid in food, easily forming stones that may affect human health. If the green tea is not properly sealed or stored in suitable conditions, it may also become contaminated with microorganisms such as bacteria and mold. These microorganisms can produce toxins during reproduction, further posing a risk to human health.

If it is necessary to prepare tea in advance, you may choose to store the tea leaves in a sealed container and keep it refrigerated. However, it is still recommended to consume it promptly to minimize nutrient loss and the risk of microbial contamination. Before consumption, carefully check the tea's color, smell, and taste to ensure there are no signs of spoilage.