Several published studies have documented a significant loss of nutrients (such as flavonoids and polyphenols) from microwaved broccoli, papaya, and the like.
Q. How safe is microwaved food?
A. Microwave cooking is fast and simple. But there can be some downsides. If you google the topic, you'll find sites suggesting a link between microwave use and cancer. While certainly disconcerting, this claim is based on just a few studies and remains greatly in dispute.
There's more solid evidence for the loss of nutrition in microwaved foods, especially fruits and vegetables. Several published studies have documented a significant loss of nutrients (such as flavonoids and polyphenols) from microwaved broccoli, papaya, and the like. Steaming, researchers found, retained many more nutrients (Journal of the Science of Food and Agriculture, 2003, vol. 83, no. 14).
The most probable red flag with microwave use seems to be the formation of toxic compounds called AGEs (advanced glycation endproducts). (These also can form during broiling, frying, and grilling.) AGEs accelerate the aging process and contribute to conditions such as heart disease and diabetes. Foods with lots of animal fats, such as cheese, sausage, or bacon, are the worst culprits for producing AGEs (Current Diabetes Reports, 2007, vol. 7, no. 3).
Using your microwave to heat up coffee, tea, and such should be perfectly safe, with no negative health effects. As always, use only microwave-safe containers for cooking and reheating.
This Q&A was written by Victoria Dolby Toews, MPH, a health journalist based in the Pacific Northwest, where she and her family enjoy hiking and cycling.