There are several reasons, one of which is overheating, which leads to explosive boiling and severe burns. Heating water and milk in the microwave can be dangerous for your home and health, according to the FDA. Although the microwave oven helps to heat various foods, in the case of water and milk, several risks can arise, ranging from home safety to the health of those who want to drink them. Several scientific studies, as well as organisations such as the FDA (US Food and Drug Administration), have warned of the dangers associated with this and recommend specific measures to avoid them.
What is the danger of heating water and milk in the microwave?
The process by which the microwave heats liquids is significantly different from traditional methods. This household appliance acts on water molecules, exciting them internally with electromagnetic waves. This excitation, far from ensuring a homogeneous temperature, can cause a phenomenon known as superheating. According to the US Food and Drug Administration (FDA), this phenomenon occurs when the liquid exceeds its boiling point without the formation of visible bubbles. The FDA warns of domestic accidents related to ignorance of the dangers of heating liquids in the microwave.
Conditions that contribute to overheating generally include containers with extremely smooth surfaces and the absence of impurities in the water. In this state, the liquid becomes unstable. A small change — inserting a spoon, a tea bag, or simply tilting the cup — is enough to cause explosive boiling, which can eject hot liquid from the container and cause severe burns. FDA reports record several domestic incidents caused by this type of accident, especially when the user is unaware of the risk.
What are the health risks?
Uneven heating is another common hazard when using a microwave with liquids such as milk. When heating in this household appliance, the heat is distributed unevenly, leading to the appearance of so-called “hot spots”: areas where the temperature is significantly higher than in the rest of the container. These hot spots are especially dangerous when preparing milk for babies, as they can cause severe burns to the child’s mouth or throat, even if the liquid appears lukewarm.
Overheating in the microwave destroys important vitamins, such as B12 and vitamins B and C, which are present in milk. In addition, rapid exposure to high temperatures in the microwave reduces the nutritional value of milk. Several studies, including one conducted by the Complutense University of Madrid, have shown that excessive heating can destroy important vitamins such as vitamin B12 and vitamins B and C. According to the US National Institutes of Health, vitamin B12 degrades significantly when exposed to high temperatures, which affects its daily nutritional value.
In addition to these losses, milk exposed to high temperatures in the microwave can alter its taste and smell and, in some cases, even burn. Often, a surface layer or ‘film’ forms due to the separation of fat, which reduces the taste qualities and alters the original texture. Experts recommend heating liquids in the microwave in short intervals and stirring to avoid risks.
How to heat liquids properly in the microwave
To minimise risks, there are certain safe practices widely recommended by experts and manufacturers:
- Heating in short intervals, stirring the liquid between each cycle, contributes to a more even distribution of heat and prevents hot spots from forming.
- Before picking up the container, let the drink sit for a few seconds.
- Choose a medium power setting so as not to overheat the liquid, destroy its nutrients, or cause splashing.
- Never heat the same liquid several times, as each cycle of temperature increase alters its composition and taste.
- It is not recommended to use the microwave to heat baby bottles: it is better to use traditional methods, such as a bain-marie or special heaters, which provide gradual and even heating. Before giving the milk to the baby, it is recommended to drip a few drops on the back of your hand to check that the temperature is suitable.
