The microwave oven, commonly known as microwave, is probably one of the most popular appliance in a kitchen all over the world. However, much has been said about its safety, advancing the hypothesis that it may release radiation or damage food. We try to shed light on this topic by studying and reporting, as always, scientific researches.
Microwave, functioning and risks
First of all, it is important to understand how the microwave works. This appliance turns electricity into microwaves, which are electromagnetic waves that influence the molecules of water, and in lesser extent also fats and sugars, of foods (Zhi et al, Mil Med Res, 2017). These molecules begin to oscillate and vibrate more and more, by colliding and producing heat, in this way the food can be cooked. If microwaves do not cause damages to food but allow just to cook it, it is not the same for humans. In fact, in 2011 microwaves were classified by the IARC as possible carcinogens even if the topic is still debated and the possible risk refers to long exposure periods (Zhi et al, Mil Med res, 2017). In any case, the microwave oven is shielded so that the waves cannot escape outside. However, there may be wave losses in the event of a dent in the door. In this case the oven must be changed.
Microwave and food properties
What happens to vitamins, mineral salts and antioxidants contained in foods after microwave cooking? Several studies have been performed to evaluate this effect. For example, a study (Lopez-Berenguer et al, J Agric Food Chem, 2007) analyzed the changes in nutrients contained in broccoli after microwave cooking. What has emerged is that the only substances that remain stable are the mineral salts, vitamin C was instead the substance that decreased the most, but there was also a loss in phenolic compounds and glucosinolates, the precursors of antioxidant substances with a powerful anticancer action. The losses of these substances are directly proportional to the cooking time. However, what has been observed is common to all types of cooking method that alter the substances contained in food. In fact, scientific studies have shown that, as regards nutrient loss, the microwave is no different from other cooking methods (Cross et al, Crit Rev Food Sci Nutr, 1982). After steaming, which is undoubtedly the best method to preserve nutrients and antioxidants in foods, microwave cooking is, together with baking, another very interesting cooking method to preserve the presence of antioxidants, while boiling as well as pressure cooking leads to the greatest loss of antioxidants (Jimenez-Montreal et al, J Food Sci, 2009 - Vallejo et al, Journal of the Science of Food and Agricolture, 2003). However, if we talk about garlic, 60 seconds of microwave cooking or 45 minutes of baking completely destroy its powerful antioxidant and anticancer substance called allyl sulfide, therefore, if we want to preserve the properties of garlic it is always better to consume it raw ( Song et al, J Nutr, 2001).
We have seen that the microwave is not a risk for health and that the changes in the properties in foods induced by this type of cooking are the same as in other forms of cooking such as baking. However, a possible risk for health related to the use of the microwave concerns the containers of foods placed then in the microwave. Scientific studies have observed that plastic containers, but only when they are not new but used for more times, release phthalates, considered endocrine disruptors, namely able to alter hormones in the body (Moreira et al, Int J Environ Res Public Health) , 2014). In general, be sure also that the container can be used in the microwave, it should appear on the packaging. Then, for what concerns other materials, you can use in the microwave porcelain containers, as long as they don’t have decorations in gold or silver. But safe are also glass containers or ceramic containers, but they should be glazed and without cracks.