We often encounter this situation in daily life: when boiled water in a kettle cools down, we plug it back in to reheat it. So, what are the risks of drinking water that has been reheated multiple times?
Can cooled boiled water be reboiled and consumed?
Reheated cooled boiled water is safe to drink.
Water boiled a second time is perfectly safe. Some may have heard that reheating cooled boiled water increases nitrite levels, potentially harming health. However, there's no need for concern. Even after multiple reheats, nitrite levels remain extremely low—well below national standards—and pose minimal health risks.
Reheat cooled boiled water before drinking
Although cooled boiled water has undergone high-temperature sterilization through boiling, prolonged cooling allows bacteria and other harmful substances to multiply. Therefore, reheating is necessary.
Risks of drinking repeatedly reheated water
1.After the first boil, nitrite levels in cooled boiled water may increase slightly, but this amount remains harmless. However, repeated boiling causes nitrite levels to multiply significantly. Such water should not be consumed regularly, as frequent intake may lead to dizziness or poisoning symptoms. Therefore, we recommend discarding boiled water and using fresh water for reheating.
2. Nitrites formed from repeatedly boiled cooled boiled water react with stomach acid in our bodies to create a substance called ammonium nitrate, which poses carcinogenic risks.