Is it true that drinking yesterday's tea is dangerous to your health?

There is an opinion that tea that has been left at room temperature for a long time cannot be drunk, as it forms substances harmful to health. We decided to check if this is true.

In the Russian-language segment of the Internet you can find many articles saying that drinking yesterday’s tea is harmful. IN blogs, on websites medical organizations and Media The authors cite a Japanese proverb: “Iced tea is worse than a snakebite.” Articles about the dangers of tea brewed the previous day, you can find at many specialized portals. In some sources we are talking not only about yesterday, but even about simply cooled down tea - supposedly drinking it Can only within 15 minutes after brewing.

We already wrote that tea, whether black or green, is very healthy. However, does it always remain this way or does brewed tea also have an expiration date?

The film that forms on the tea leaves after some time can really cause concern. Scientists have differing opinions about what kind of film this is and why it is formed. Alone claim, that the calcium bicarbonate contained in hard water is to blame for everything, which, when mixed with polyphenols - the most useful part of tea - forms that very rainbow film. Other bow down to the version that this film is essential oils from the leaves, released into the water and floating to the surface. But whatever the reason for the formation of this film, we were unable to find scientific studies that would confirm that it is harmful to health. 

What really can be dangerous about yesterday's tea is bacteria that can begin to multiply in it at room temperature. The tea leaves themselves do not contain any hazardous substances, but bacteria can get there during production, transportation, storage and preparation. Therefore, specialists advise Brew tea and herbal infusions, which are also often called teas, with boiling water, as this will help destroy most pathogens. However, even in this case it turned outthat in tea brewed more than 16 hours ago, E. coli begins to actively multiply, which can really be dangerous to health. Moreover, if the tea brewing temperature was not high enough, its shelf life may be even shorter.

The type of tea also affects the shelf life. So, biologists conducted experiment, during which they took three types of tea (black, oolong and white), brewed it with boiling water and left it in sterile containers at room temperature for two days. Even under such laboratory conditions, which are clearly not observed at home or in catering establishments, bacteria began to actively multiply in white tea and oolong. Scientists attribute this to the degree of oxidation of tea - in the most oxidized black tea there were no visible changes after two days, while in white tea, which did not oxidize at all, there were the most bacteria.

If you still hate to pour out the tea, it is better to put it in the refrigerator overnight, since the “room” temperature creates excellent conditions for bacterial growth. In conditions from 4.5 °C to 60 °C, the number of these microorganisms grows exponentially - doubling every 20 minutes. If we are talking not just about brewing in a teapot, but about a finished drink, to which we have added sugar or milk, then its shelf life outside the refrigerator is even shorter, since these additives can create an even more nutritious environment for bacteria.

Adviсe Brewed tea can be stored for no more than eight hours meet on many portalswho specialize in this drink: it talks about both the danger of bacterial growth and the fact that over time the taste and aroma of tea deteriorate. Some sites even refer on recommendations The US Centers for Disease Control and Prevention do not drink tea that has been left out of the refrigerator for more than eight hours, but we were unable to find their original source.

Thus, tea can actually spoil and then become harmful to health, especially if mold has already begun to form in it. However, to do this, it must be kept at room temperature for quite a long time. Bacteria begin to multiply faster than mold, and indeed pose some danger to the body. In general, tea brewed more than eight hours ago is really not worth drinking, at least because it loses its taste. But calling such a drink poison is still an exaggeration.

Half-truth

What do our verdicts mean?

Read on the topic:

1. Is it true that green tea is healthier than black tea?
2. Is it true that boiling water “kills” the beneficial properties of tea?
3. Is it true that drinking during meals is bad for digestion?