Microwave Ovens and the
Healthfulness of Microwaved Foods

by Debra Lynn Dadd

Microwave ovens do have benefits. They are certainly convenient. They are more energy-efficient than other cooking methods. But are they safe? And do they produce food that contributes to the health of our bodies?

While there is not enough evidence to require warning labels on microwave ovens, or to remove them from the market, there is concern both about the safety of our exposure to microwaves and the healthfulness of microwaved food.


Even microwave ovens that are functioning perfectly emit microwaves. Safety standards set by the US Food and Drug Administration (FDA) allow microwave emissions of up to one milliwatt per square centimeter (1mW/cm2) when the oven is purchased, and up to 5mW/cm2 after the oven has been in use. Studies on industrial exposure recommend that daily exposure should not exceed one milliwatt for more than one minute. Average home use of microwave ovens far exceed this.

Workers who are exposed to microwaves on the job experience headaches, fatigue, irritability, sleep disturbances and other symptoms.


Advocates of microwaved food claim that it is healthier because it retains vitamins, but the University of Minnesota disagrees:

"Microwaves ... are not recommended for heating a baby's bottle...Heating the bottle in a microwave can cause slight changes in the milk. In infant formulas, there may be a loss of some vitamins. In expressed breast milk, some protective properties may be destroyed.... Warming a bottle by holding it under tap water or by setting it in a bowl of warm water...is much safer".

If heating formula in a microwave can cause it to lose vitamins and protective properties in breast milk to be destroyed, then it can do the same to the foods we eat. While the effects may not be immediately observable, a regular diet of microwaved food may have long-term health consequences.

Two Swiss researchers found that microwave cooking changes food nutrients significantly. Blood samples taken from eight individuals immediately after eating microwaved food revealed, among other things, an increase in the number of white blood cells--often a sign of poisoning.

Safety tips for using microwave ovens

I personally have never had a microwave oven in my own kitchen and am finding that it had been difficult to get people to give up their microwave ovens. Some of the generation who grew up with microwave ovens apparently don't know any other way to heat food (really!).

If you choose to use a microwave oven, Consumer Reports magazine suggests you stay as far as possible from the oven while it is in operation.

In addition, operate and maintain the oven in ways that minimize leakage:

* make sure the oven door closes properly

* prevent damage to hinges, latches, sealing surfaces and the door itself, and make sure these are in good working order

* make sure no soil or food residues accumulate around the door seal

* avoid placing objects between the sealing surfaces.

For peace of mind, test your oven for leakage. Testers can be purchased online.

When cooking in a microwave, use heat-resistant glass, not plastic. The Food Safety Inspection Service (FSIS) of the USDA warns against using foam trays, plastic wraps, and cold-storage containers such as margarine tubs, whipped-topping bowls and cottage cheese cartons. According to the FSIS flyer "A Microwave Handbook," these containers "are not heat stable at high temperatures. They can melt or warp from the food's heat, possible causing chemicals to migrate into the food."


Hailed as "The Queen of Green" by the New York Times, Debra Lynn Dadd has been a leading consumer advocate for products and lifestyle choices that are better for health and the environment since 1982. Visit her website - http://www.debraslist.com - for 100s of links to 1000s of nontoxic, natural and earthwise products, and to sign up for her free email newsletters.

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