When it comes to the science of wellness, distinguishing the facts from the urban legends can be tough. That’s why we’ve enlisted Darya Pino – a scientist, foodie, and self-proclaimed geek girl. Check out the ZocDoc Blog every Tuesday to see her bust the biggest myths in health. Enjoy!
The interwebs are teeming with speculation that microwave cooking can do anything from destroy the nutritional value of your food to turn harmless compounds into carcinogens. But is there any truth to these claims?
To start, it’s helpful to understand how microwave cooking works. Microwaves are a very low frequency wave on the electromagnetic spectrum. They have slightly more energy than radio waves, and significantly less energy than visible light. Microwaves are a non-ionizing form of radiation, meaning they are not powerful enough to impart radioactivity to other substances. When applied in intense doses, however, it can cause polarized molecules to rotate, creating friction and heating the substance. This is how a microwave oven warms your food.
For this reason, the greatest danger from being exposed to microwaves is burning. If the seal on your microwave oven is compromised and your skin or eyes are near this area, there is a slight risk of injury. Luckily, microwave construction over the past several decades has become very efficient and it is extremely unlikely your microwave is leaking. If you are worried that your microwave might be leaking, it is probably time for a new one.
In practice, however, microwaves themselves are very unlikely to burn you. Instead, the biggest danger is burning yourself on the food you heat with your microwave oven. Because microwaves heat food fairly rapidly, microwaving can result in foods and liquids “superheating.” This is when water gets so hot that it cannot turn to steam fast enough, which essentially traps the steam inside. When this happens, a simple stir or other disturbance can cause the substance to erupt, spilling out over the container and potentially burning your hands or face. To avoid this, refrain from heating your food or drink for too long, and always wait 20 seconds or so before removing it from the microwave. Most important, always be careful and work slowly when moving or tasting microwaved items.
But can’t microwave heating turn harmless food compounds into dangerous chemicals? All of the articles I’ve seen espousing the dangers of microwave cooking cite the same two articles, neither of which was peer-reviewed or replicated by other labs. In fact, the vast majority of scientific studies investigating the effects of microwave cooking on food suggest the exact opposite: that microwave heating is often safer than conventional cooking methods.
The reason for this is that most cooking methods, particularly grilling and frying, expose the surface of foods to very high temperatures. In meats, these high temperatures cause the formation of substances called hydrocyclic amines (HCAs), which have been shown to cause several kinds of cancer in laboratory animals. Population studies have also suggested that people who eat a lot of grilled or fried meats have higher cancer risk.
Microwave heating eliminates the majority of the precursors for the formation of HCAs, and reduces their mutagenic activity by 95 percent. Other studies have shown microwave cooking is associated with a decreased risk for some cancers. For the best of both worlds (since we all know grilled meats taste far superior to microwaved meats), gently cook your meat in the microwave, in a low conventional oven, or sous vide, and finish it on the grill for flavor.
What about vitamins? Doesn’t microwaving destroy all the nutritional value of foods? On the contrary, most studies show there is little difference in nutrient value of foods cooked in a microwave and foods cooked by other methods. Certain delicate vitamins like vitamin C are damaged by heat, and microwave heating is no exception. Fortunately vitamin C is plentiful in fruits and vegetables, so eating a wide variety of raw and cooked food covers your nutritional bases.
Lastly, it is always a good idea to leave plastics out of the microwave. The reason for this is that all plastics are capable of leeching bioactive chemicals into food, and this effect is worsened when the foods are heated. If your food is in a plastic container, be sure to transfer it to a microwave safe dish before heating it.
Image: Nuke’d Food, a Creative Commons Attribution (2.0) image from Instant Vantage’s photostream.