How safe is microwave cooking?

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Microwave oven uses electromagnetic waves to heat up food. When the oven is switched on, electromagnetic waves will spread across the oven and be reflected by the inside of the oven. Water molecules in the food will vibrate when these microwaves pass through it and thus the food is heated up.

The question that often arises among us is "Will the microwaves affect us?"

The electromagnetic waves in theory should not leave the oven. Microwave ovens are designed in such manner that the waves are contained inside the oven and will only be active when the oven is switched on. Microwaves are not absorbed through the oven wall. But there is a possibility of microwave leakage if the oven is faulty.

So what happens if our body come in contact with the waves? The molecules in our body will vibrate and heat it up. But only certain organs in our body are sensitive to heat, such as eye balls and genitalia.

For the small amount of microwaves to cause heat induced damage, two conditions need to be met

i) There must be leakage from your microwave

ii) There must be significant time of exposure, which is rare as cooking in microwave oven is commonly just for a short time.

"Many nutrients break down when they're heated, regardless of the source"

So we can confidently decide that microwave oven will not harm us, except if the unit is faulty in which there is a small possibility of wave leakage.

What about the food heated or cooked using microwave oven? Does microwave heating change any molecule that might make food carcinogenic ( ability to cause cancer )? Does it remove the nutrients of the food?

Key issue to understand is that microwave oven cook by production of heat. And many nutrients break down when they're heated, regardless of the source. 

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A research done by Monreal J et al specifically compared effect of different cooking methods on anti-oxidant level of vegetables showed that microwave cooking has the lowest effect on the anti-oxidant level of vegetables such as celery and ginger. Boiling them has the highest effect,causing the vegetables to lose their anti-oxidant properties.

Essentially all cooking method will make some nutrients to break down. The key is to reduce the amount of time the food is exposed to heat. Microwave oven heats up quickly, thus reducing the amount of time the food is exposed, and effectively reducing the amount of nutrient loss compared to other cooking methods.