MYTH OR REALITY – Although largely implanted in our kitchens for thirty years, the microwave is still subject to fears about its effects on health. To unravel the true and false, we interviewed Jean-Michel Court, physicist and professor of physics at Sorbonne University.
With its turntable and soft roar, it is an integral part of our daily lives. Invented after the Second World War and popular since the 90s, the microwave has established itself as an indispensable element in our kitchens. But while nearly 90% of French homes have one at present, this device is simple and fast to use is still suspected by many of us to have adverse health effects. Should we continue to use it? Is it better to leave when it is running? We asked Jean-Michel Court, physicist and professor of physics at Sorbonne University, to know if he was, yes or no, object non grata in our kitchen.
A food just as transformed with another cooking method
The microwave oven uses high frequency radio waves produced by an electron tube called a magnetron. These waves, totally reflected by the metal walls, are however absorbed by the water molecules that make up our food or our drinks. Reacting to this electric field that changes direction a billion times a second, they rotate on themselves and collide with their neighbors. “It’s the same thing as when you have waltz on a dance floor a little crowded: if you turn fast and you collide with a couple that is next, you tend to project,” says Jean -Michel Court, co-author of the book “En avant la physique!” It is this agitation that ultimately creates the desired heat.
But then, a food whose molecules have been agitated by radio waves is it denatured, transformed? “When you cook something, what is your goal? What you want is to transform your food, so of course the food is transformed when you place your food in the microwave!” Says the physicist. However, he explains, processing a food cooked in the microwave is no different from a food cooked in the oven or pan. This depends only on the temperature at which the food is heated. Thus, a food cooked at 100 degrees in the oven, the pan or the microwave will undergo the same chemical changes.
“The only difference is how the different parts of the food are cooked. When you put a roast in an oven, the surface, which will be heated by air and infrared radiation, will be very brown If you put the same roast in a microwave oven, you will have an even cooking because the microwave has the particularity of heating and cooking, cracked and a little grilled, and you will have the inside more bleeding. All parts of the food in the same way, “says Jean-Michel Court.
The microwave oven, guaranteeing a good preservation of nutrients
The only “danger” that can watch your plate is the loss of the nutritional quality of the heated food. But, for the phobic of the microwave oven, it would actually represent one of the best options to preserve the best nutrients. “If you’re cooking in water, the problem is that the right nutrients will go into the cooking water, hence the interest of steaming … or microwaves!” Antioxidants, which prevent premature aging of the skin or even certain diseases such as cancer, will be partially destroyed. But in the same proportion as with a cooking with steam or water, assures the physicist.
When the appliance is off, there is no microwave
No danger either from the waves that were used to heat your dish once it came out, says Jean-Michel Court. “When the device is off, there is no more microwave in the oven or in the food. It is like when you turn off your phone: it no longer emits,” gives as an example that which is also a professor at the Sorbonne. In a document specifically dedicated to the appliance, the World Health Organization (WHO) also insists on this point: “It is important to realize that the food cooked in a microwave oven does not become “radioactive”. In other words, there is no risk of your body being irradiated by eating microwave-heated food.
The scientist, however, warns about a real risk: that of boiling late. The walls of the containers are not heated by microwaves, they offer no grip on vapor bubbles that may form during boiling. But the slightest element entering the heated liquid a few seconds after it leaves the microwave, like a square of sugar, allows these bubbles to form, resulting in a late boiling likely to overflow the liquid from its container and you burn. “If you have to wait about thirty seconds before eating or drinking a food that comes out of the microwave, it is because of this type of phenomenon that remains, in practice, very rare,” says Jean-Michel Court.
When plastic containers and heat do not mix
However, be careful not to place your food in inappropriate containers for heating in the microwave (it is also valid for baking or in the pan). For example, avoid storage boxes and other plastic dishes, which can release toxic substances such as endocrine disruptors under the effect of heat. If you have no other choice, make sure at least that the plastic is as safe as possible by checking that it has the numbers 2, 4 or 5 surrounded by a triangle. Containers marked 7 contain Bisphenol A, an endocrine disruptor which is now banned from sale in France, but which may still be in circulation. “If you have some, do not use it,”UFC-Que Choose on his site.
Other fears relate to approaching a microwave on the move. Again, the risks would be non-existent for a furnace in good condition, although leaks are possible. Several countries and institutions such as the International Electro technical Commission (IEC) and the European Committee for Electro technical Standardization (CENELEC) have set an exposure limit of “50 watts per square meter at any point 5 cm away from external surfaces of the oven, “says WHO, which states that in practice these emissions are” considerably below this international limit “. “Fifty watts is not a lot,” says Jean-Michel Court, “When you’re in the sun on the beach in the summer, you’re taking 1,000 watts per square meter of solar energy.”
These levels of radiation, far from those to which bodily injury has been observed in humans, would decrease more rapidly with distance. “For example, a person 50 cm away from the oven receives only about one-hundredth of the exposure of someone who would be 5 cm away,” says WHO.
It’s not like with mobile phones
“Knowing that the microwave started to develop in the 70s and 80s, we are still at 40 years of intensive use. If there were real public health concerns caused by the microwaves the statistics would have shown it, especially since this use has not been uniform within the populations, which offers the possibility of making comparisons between those who have used it or not. There is no effect highlighted. It is not like with mobile phones for which there is less recoil, “concludes the physicist.
Some associations, such as the Center for Research and Information on Electromagnetic Radiation (Criirem), still criticize the scientific community for not having conducted enough studies on the subject. “In relation to food, we have absolutely no data that allows us to say whether it is dangerous or not,” notes Catherine Gouhier, the president of Criirem. “Second thing: the microwave oven emits radiation within a radius of 2.5 meters around the oven when it is at full power. There is, of course, a maximum emission standard, but it does not take into account short-term effects: there is no long-term standard, whereas WHO has placed this type of radiation in the category of potentially carcinogenic physical agents”