Loved by some and disowned by others, the microwave is the lifeline for those of whom cooking is an indecipherable science and somewhat detestable for those who believe that it affects food, but really, how bad is it to cook in the microwave?
First of all, it must be made clear that, if used correctly, there is nothing to worry about when it comes to microwave radiation, according to the World Health Organization. But there are other concerns that are not as clear, such as whether microwaved food suffers from nutrient loss or whether heating plastic food can trigger hormonal disruption.
Some research has shown that vegetables lose some of their nutritional value in the microwave.
Does it remove nutrients?
Microwave, it has been found, removes 97% of the flavonoids (plant compounds with anti-inflammatory benefits) from broccoli, third more damage that is caused by cooking.
“Moderate heat treatment could be a useful tool to improve the health properties of some vegetables”
However, another study showed that shorter cooking times (broccoli was microwaved for one minute) did not compromise nutritional content, even that microwave seemed to be a better way to preserve flavonoids than steam.
According to lead researcher Xianli Wu of the Beltsville Human Nutrition Research Center at the United States Department of Agriculture, there is no clear answer on whether vegetables in the microwave retain more nutrients than any other method. This is because each food is different in terms of texture and nutrients.
In another study, researchers compared the phenolic content (compounds associated with various health benefits) of a number of vegetables after they have been boiled, steamed, and microwaved. Microwave and steam caused a loss of phenolic content in squash, peas, and leeks, but not spinach, bell peppers, broccoli, or green beans.
The researchers also tested antioxidant activity, and on both measures, the vegetables performed better in the microwave than when boiled. “Moderate heat treatment could have been a useful tool to improve the health properties of some vegetables,” the researchers noted.
Is plastic packaging safe?
We often microwave food in plastic containers and wrappers, and some scientists warn of the risk of ingesting phthalates. When exposed to heat, these plastic additives can break down and leak into food.
Phthalates, present in plastic packaging, can alter hormones and metabolism and have been linked to fertility problems and asthma
“Some plastics are not designed for the microwave because they have polymers inside that make them soft and flexible,” explains Juming Tang, professor of Food Engineering at Washington State University (United States). “These melt at a lower temperature and can leach (separate their soluble parts from the insoluble ones) during the microwave process if they exceed 100 degrees Celsius.”
In a 2011 study, researchers bought more than 400 plastic containers designed to hold food and found that most of them were leaking hormone-altering chemicals.
Phthalates are one of the most widely used plasticizers, added to make plastic more flexible and often found in take-out packaging, plastic wrap, and water bottles.
They have been found to alter hormones and our metabolic system. In children, phthalates can increase blood pressure and insulin resistance, which can increase the risk of metabolic disorders such as diabetes and hypertension. Exposure has also been linked to fertility problems, asthma, and attention deficit hyperactivity disorder.
The bisphenol (BPA) is also commonly used in plastic products, and studies have suggested that hormones may also alter. But research is limited, compared to the number of studies looking at phthalates.
No safe level of exposure
“The microwave mobilizes pollutants,” says Rolf Halden, professor and director of the Center for Biodesign for Environmental Health Engineering at Arizona State University (United States). “This process is used in laboratories to extract contaminants from samples, prior to chemical analysis.”
And the potential risks do not necessarily increase with how often an individual bakes food in microwaves in plastic containers, but low-level exposures are where most of the effects occur, so there is no safe level of exposure.
The best way to minimize risk is to use other non-plastic microwave materials, such as ceramic. If plastic containers are used, those that are losing their shape should be avoided, as old and damaged containers are more likely to leach chemicals.
You should also check the universal recycling symbol on the container, those with the “PVC” include phthalates.
Uneven heating and high temperatures
Apart from plastic, there are other potential risks of heating food in the microwave, such as uneven heating and the high temperatures used.
Try to use the microwave for reheating, not cooking, and you should not reheat a meal more than once
The first thing to try is to use the microwave to reheat, rather than to cook food, as they can be cooked unevenly. “Temperatures will be different in a cross-section of the food. It is difficult to achieve a completely uniform temperature, especially when it comes to raw food,” says a BBC Francisco Diez-Gonzalez, Professor of Food Safety at the University of Georgia (United States ).
However, reheating food also carries risks. Food should be heated to 82 degrees to its full extent to kill any harmful bacteria and since bacteria can continue to grow each time the food cools down again, food should not be reheated more than once.
The high temperatures of the microwave may also pose some risk. In general, high temperatures are not a problem, but there is some research to suggest that there is a risk associated with microwave cooking of some starchy foods, such as grains and root vegetables.
It may appear chemical acrylamide, a natural byproduct of cooking. Animal studies have shown that acrylamide acts as a carcinogen because it interferes with the DNA of cells, but the evidence in humans is limited.
Going back to the initial topic, microwave radiation is completely harmless. Microwaves use low-frequency electromagnetic radiation, the same as that used in light bulbs and radios. When you put food in a microwave, it absorbs these microwaves, causing the water molecules in the food to vibrate, causing friction that heats the food.
Radiation without danger
“Microwaves are part of the electromagnetic waves that we are exposed to on a daily basis. When you bake bread, you are exposed to electromagnetic waves and the infrared energy of the oven’s heating elements. Even people exchange radioactive waves with each other,” Tang concludes. “If you’re eating crops grown in sunlight, you shouldn’t worry about microwave food.”