10.28.2011

Dear PWN,

What impact does microwaving food have on its nutritional content? I have heard that microwaving devoids food of its nutrients, more so than heating on a stove. I am hoping that is false.

-John from University City, MO


The microwave question. We’ve all asked it at one point or another, and maybe we’ve even opted out of researching it in fear of what we’d find.







I actually do not own a microwave. We had a little one that had Ed inherited before we even met, and it was such an eyesore on our counter, and so rarely used, that we decided to get rid of it. I can honestly say that I don’t even miss having one around. If I ever designed a new kitchen maybe I’d designate a place for a microwave, but for now we don’t really need one.


However, I am still very interested in the topic of what different cooking methods do to nutrients in food. I did a little research, and here is what I found:


The main methods used for cooking vegetables are boiling, steaming, microwaving, or stir-frying. All types of cooking alter the food in some way. Generally speaking, the more heat used, the more nutrients and enzymes are destroyed.


Any time vegetables are cooked in water, greater nutrient loss occurs. The water leeches nutrients and, unless the water is used in the final dish, these nutrients are lost. Water-soluble vitamins include vitamins B and C, which are abundant in fresh vegetables. These are the most heat sensitive vitamins, and therefore are easily destroyed.


A study published in The Journal of the Science of Food and Agriculture (2003) found that when vegetables were microwaved in water, they lost 74% - 97% of their antioxidants. A 2009 study came up with similar results: broccoli that was boiled or microwaved retained fewer nutrients than broccoli cooked without as much water, such as by steaming or stir-frying. Other studies I found, however, were inconclusive as to whether or not microwaving foods was more nutrient-destructive than other cooking methods.


Despite the conflicting information on this subject, one thing is certain: microwaving does deactivate enzymes, which are useful when it comes time to digest the food. Other cooking methods can also deactivate at least some enzymes. That being said, gently cooked foods are typically easier to digest than raw foods for other reasons. My recommendation would be to lightly steam your veggies for maximum nutritional benefits. If you boil them, use the water as a base for a soup to get all the important nutrients from the vegetables. If you microwave vegetables, use as little water as possible and only heat them for a short period of time. Most of the research I found was on cooking veggies, but I believe these conclusions would apply to all types of food.


And, of course, never microwave in plastic. Glass or non-leaded microwaveable ceramic is best.

Sources

“Effects of different cooking methods on health-promoting compounds of broccoli” by Gao-feng Yuan, Bo Sun, Jing Yuan, and Qiao-mei Wang (2009

“The Claim: Microwave Ovens Kill Nutrients in Food” by Anahad O’Connor (New York Times, 2006)

www.medicinenet.com



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