Is microwaving an unhealthy method of cooking food? Interesting question. Microwaves certainly seem creepy. Do they mutate food into unhealthy, nutrient depleted shells of what they once were? What I looked into about microwave cooking is essentially this: Does it destroy nutrients and does it create dangerous compounds?
Elimination of good stuff:
A while back, the Perfect Health Diet blog discussed the effects of microwaves on reducing flavanoids, finding the effect to minimal or better than other cooking methods in green tea, onions, strawberries, purple potatoes, and 9 assorted vegetables.
This study by the national center for home food preservation examined the effect of microwave blanching vs. boiling water blanching on the retention of several vitamins in turnip greens.
As you can see, boiling caused an almost complete loss of vitamin C, folic acid, thiamine, and riboflavin. The effect was significantly less when microwaved.
The effect of microwaving vs. baking on spinach in this study found that ascorbic acid retention was 47% vs. 51% (a relatively minor difference) and folate retention was 101% vs. 77%, meaning that folate was not decreased at all in the microwaved spinach, but was notably reduced in the conventionally cooked spinach).
Overall, most studies I have seen show vitamin loss is not much different in microwaved food than food cooked other ways.
Production of bad stuff:
Peroxidation of polyunsaturated fatty acids during cooking is a concern of mine and it appears that microwaving and conventional cooking methods don’t differ significantly in their production of these compounds (see this study and this study)
Acrylamide, a possible carcinogen produced when cooking starchy foods like potatoes, may be increased in microwaving compared to frying and baking. I’ve found some contradictory results regarding this though, so I’m not fully willing to say one way or another.
Some people seem very opposed to the idea of microwaves just on principle. In addition, there are a lot of anti-microwave arguments, most of which seem to misrepresent science. I may amend this post to add a debunking of many of those arguments, but for now I’ll leave it. From what I’ve seen the effect of cooking with microwaves is just like any other method of cooking and likely is not “bad” relative to baking, frying, or boiling. Don’t fear the microwave.