Walk into almost any kitchen in America and you will likey find a microwave. What was once a high-tech item can now be purchased for less than $100. The microwave has created a revolution of frozen dinners that can be prepared in just a few minutes, only to be consumed just as quickly. But is there a price to pay for this kind of convenience? 

There is no argument over the convenience of the microwave. The availability of the device has allowed for grocery stores to line freezers with quick breakfast, lunch and dinner options, a host of microwavable meals already prepared and preserved. But is food up to this fast-cooking challenge? How well will the food do in retaining its nutrients after going through a blitzkrieg of microwaves? What does the science behind the microwave tell us?

The data behind microwave cooking is surprisingly sparse. The technology and excitement of such a helpful tool has quickly surpassed any considerations as to the safety of the cooking method, making it a secondary issue. In truth, any cooking method, including grilling, broiling and pressure-cooking all have the possibility to destroy some of the active nutrients in food. Microwaves seem to be no different. One study examined broccoli cooked in water in a microwave [Source: Lopez-Berenguer]. It appears that the longer the broccoli was cooked and the more water used, the greater the loss of nutrients from the food, including vitamin C. A second study showed losses of vitamin B-12 from microwaved pork, beef and milk [Source: Watanabe]. 

A common theme with all methods of cooking that is especially true with microwaves, is that the longer food is cooked, the more the nutrients are damaged or destroyed. A study on dairy products demonstrated significant damage after 5 minutes of cooking and even more damage after 10 [Source: Herzallah]. Sixty seconds of microwave cooking can actually destroy the health-promoting properties of garlic [Source: Song]. Additional research comparing various cooking methods noted that microwaving and grilling vegetables were probably the worst options in regards to retaining various vitamins in the food [Source: Ryan]. Unfortunately, this means that meat, vegetable and milk products might all be adversely affected by microwaving. This results in less nutrition in food with significantly less benefits to the body.

To be fair, all the news is not negative for the microwave. Some studies found that microwave heating was not as hard on the food. One study compared how well the healthy fat content of fish (herring) did in a microwave versus a conventional oven. This study found no major damage to the healthy fats in either cooking method [Source: Regulska-Ilow]. A second study found that microwave heating did not damage vitamins B-1 or E or the essential fatty acids in human milk [Source: Ovesen]. If the temperature of the milk was elevated past 60 degrees Celsius (140 degrees Fahrenheit) the immune benefits of breast milk were lost. This differs from the damage seen with the loss of B-12 from microwave use. Another study suggested that heat from an oven or microwave might improve iron absorption from cereals [Source: Hemalatha]. However, this same study also found that microwaves limited the amount of zinc that could be absorbed from the same grains.

Let’s clarify a few points that seem to be true based on evidence:

  • Though not all of the vitamins and minerals are affected by microwave cooking, some certainly are even more so than with regular cooking.
  • The longer and hotter something is cooked in a microwave, the greater the chance that there have been significant or even total losses of nutritional content.

It is suggested to only use glass when cooking in a microwave. Cooking foods in plastic (even microwave meals sold in plastic) raises the concern of leaching the plastic chemicals into the food. Cooking in glass will limit this risk substantially and help limit toxic exposure. This is especially important for children’s meals. The destruction of some vitamins from the microwave, along with the addition of plastic toxins from the container, is a one-two punch best avoided.

The greater problem then becomes that regular, long-term use of microwaves might significantly decrease the available nutrition in food, leading to a greater possibility of chronic illness. Chronic illness such as heart disease, diabetes and arthritis is rampant in the United States and poor nutrition is very much a cause of this. Please recognize these points when cooking. Keep in mind that no matter how convenient food can become, optimal health will always be worth your time.