Microwaves Don’t Destroy Nutrients

by Brian Rigby, MS, CISSN

2 Replies

Nutrition Myths

Are microwaves nutritionally dangerous?

Microwaves are victims in the cooking world. Their rank on the hierarchy of kitchen appliances sits somewhere below waffle iron, and perhaps just above ice cream maker. Most people wouldn’t consider their kitchen complete without one, but it’s never a star. Nobody loves their microwave. This is a shame because microwaves are perhaps the greatest improvement in cooking technology since the fire, not because they are perfect for every job, but because they’ve made good nutrition so much easier, cheaper, and faster.

Of course, microwaves have also made bad nutrition much easier, which ultimately is perhaps the biggest reason they are vilified—anything that can make food preparation that easy (whether healthy or not) must be hiding a dirty secret. I assure you, they are not.

Microwaves are absolutely safe—nutrition-wise, health-wise, food-wise. Microwaves are simply a more efficient way to heat food; they cannot destroy nutrients anymore than any other form of cooking. Whether you use your microwave to prepare TV dinners or steamed broccoli is up to you—either way, the nutritional content of your meal is 100% in your hands, not the machine.

Get to Know Your Microwave

Microwave radiation is invisible. We cannot see it as our food slowly rotates, nor can we feel it thanks to the oven’s lining. We cannot “experience” a microwave in the same way we can a fire or an oven, where the heat is plain as day. When we open a microwave to retrieve our food, it is as cold and sterile as when we placed our food in it (save for a bit of steam). The appliance exudes no warmth, provides no light; the power it wields is intangible, mysterious.

If a caveman came across a working microwave, and figured out how to use it, it would appear as magic—you put food in, and it comes out hot. We’re not cavemen, however; we’re modern humans of science! We can easily understand how a microwave works, if we choose, and see that it works… well, in a very similar fashion as any other cooking method. In the end, they’re as mundane as their position on the kitchen totem pole implies.

Microwaves are a type of radiation—an emission of energy at a specific wavelength. Radio waves are a type of radiation too, at a wavelength suitable for long-distance broadcasts of information. Every color we see in the world is the result of radiation, with specific colors corresponding to specific radiated wavelengths. The heat you feel from the sun is radiation (infrared), as is a portion of the heat you feel from a fire or an oven (also infrared). Radiation is everywhere, because energy is everywhere and radiation is how that energy moves.

No matter how you cook your food, the reason it gets hot remains the same: energy transfer. The molecules that make up your food are all bouncing around, and when they start to bounce faster they become “hot”. This energy transfer is achieved through radiation (as well as convection and conduction), and thus all cooking methods are ultimately very similar in their end-result.

Most of the ways we cook food involves heat transfer from the outside in. It takes a long time because the energy must be transferred molecule to molecule, from the outermost molecules to the innermost ones. Microwaves are faster because they can penetrate the outside of the food and transfer energy to the innermost molecules simultaneously with the outermost ones. This makes microwaves dangerous to be exposed to if you’re a human, but very efficient at cooking. Microwaves wouldn’t cause cancer (they’re not an ionizing type of radiation like ultraviolet), but cooking your liver through your skin would be at least equally unpleasant if not more so, and so we make sure no microwaves can escape our ovens.

Microwaves & Food Nutrition

Do microwaves destroy nutrients? No. Or at least, no more than any other cooking method. Microwaves simply transfer energy, and whether or not that energy destroys nutrients depends on the total energy added (heat) and the length of time it’s added for (cooking time).

In fact, because microwaves are so efficient at cooking, microwaves should hypothetically minimize nutrient loss. The clinical relevance of this is questionable since any nutrient loss would be minimal (only a handful of nutrients are susceptible to heat, or “heat-labile”), and the temperature and time food is exposed to in the kitchen during most normal methods of cooking is not sufficient for large-scale nutrient destruction.

Side Note: We know biochemically that most nutrients are stable, but testing this in the laboratory with real conditions often leads to different results. This is because different cooking methods could result in nutrient loss through other means, such as loss to water. Regardless, we can be assured that cooking doesn’t lead to enough nutrient loss to cause any sort of health problem (at least in the vast majority of people) because nearly 100% of people cook, and have so for tens of thousands of years, and we’ve yet to see an epidemic of nutritional deficiencies as a result.

If you’re trying to avoid nutrient loss, the only big thing you should avoid is boiling your food—many vitamins are water-soluble and will be leached out of the food during a long boil. Again, the clinical significance is questionable, and if you later consume the liquid used to cook (such as for a soup) you’ll get all those nutrients back.

The bottom line is that microwaves don’t destroy nutrients, heat destroys nutrients. If you want to avoid nutrient loss, don’t overcook your food regardless of the method. Or just don’t worry about it at all because your health probably isn’t going to suffer unless you’re carbonizing everything.

Don’t Fear the Microwave

Microwaves have made it easy for millions of individuals and families to improve their nutrition. Not everyone has the time to cook vegetables for every meal, or the money to afford fresh produce—microwaves allow these folks to buy a pound of broccoli for $1.50 and have steamed greens to eat in less than five minutes.

As long as there are those who disparage the microwave, though, we’ll continue to have ridiculous controversies over whether they’re nutritionally appropriate. They are. They don’t destroy nutrients, they aren’t dangerous, and the end-result of their heating is the exact same as any other cooking method, just faster.

So please, don’t fear the microwave. Embrace it.


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2 comments

  1. patrick

    please do an experiment:

    get a package of seeds…any types…split them into three groups…

    germinate them as so: regular tap water is our control group…

    now take that same tap water, microwave it, let it cool down…test group #1…

    now take tap water and boil it, let it cool and germinate…test group #2…

    compare the germination rates of all three groups…please post update/results 🙂

  2. Brian Rigby, MS, CISSN Post author

    This is a widespread myth that has been repeatedly debunked:

    http://www.snopes.com/science/microwave/plants.asp

    There is nothing microwaving can do to molecularly change the structure of water—H2O—aside from causing it to vaporize into steam. Any water that remains unvaporized will be objectively impossible to distinguish from water that has been boiled, let sit, frozen, or manipulated in any other way that doesn’t involve the introduction of new molecules.

    If, on the other hand, you microwaved the seeds, then you would see worse rates of germination—but the same would happen if you baked or fried the seeds, too! The nutrition will be unchanged, but the heat (from any source) will denature the enzymes that signal a seed to sprout and thus cause it to be inert.

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