Does microwave cooking improve or degrade foods?

Getting Steamed

A shrill screeching of brakes cut through the morning calm…

But it wasn’t brakes on a car – it was a sound that occurred only in my head (metaphorically speaking) while listening to an NPR broadcast about food preparation and nutrition.

It was actually an insightful piece. Until everything (for this listener anyway) came to a screeching halt.

Are you missing out?

Did you know that when a salad is eaten with fat-free or low-fat salad dressing your body doesn’t absorb carotenoids as well as when you use an oil-based salad dressing, such as olive oil?

You do know about this nutritional quirk if you happened to catch an e-Alert I sent you about five years ago, or if you were listening to the NPR broadcast I heard on a recent morning.

Carotenoids, of course, are organic plant pigments in colorful fruits and vegetables. And they’ve been shown to have antioxidant activity that supports immune function, vision health, and protection from DNA damage. So if you’re dousing your salads with “healthy” dressings that skimp on fats, you’re actually missing out on one of the most important reasons to eat salads in the first place!

The NPR report went on to note that carotenoids are also better absorbed when fruits and vegetables are chopped or grated. And gentle cooking may help release the nutrients in some foods such as carrots. (In a previous e-Alert I told you how the body better absorbs lycopene, an important carotenoid, when tomatoes are cooked and combined with some sort of oil.)

And according to NPR, a recent Spanish study tested six different cooking methods on 20 different foods and found boiling and pressure cooking led to the greatest loss of nutrients. Surprisingly, however, the foods tended to retain antioxidants better when they were microwaved.

Cue screeching of brakes, crashing noise, amusing sound of hubcap spinning to a halt.

Don’t catch that wave

Obviously we’ll need further studies to confirm the Spanish results. But for the moment we’ll say, hypothetically, that foods cooked in a microwave oven really are more antioxidant-rich than foods cooked by other methods. Fine. Got to love it. Antioxidants are vitally important to your health.

But the antioxidant content of a cooked food is just one component of nutrition.

In an e-Alert I sent you several years ago, HSI Panelist Allan Spreen, M.D., walked us through a few reasons why microwave cooking might be harmful to food and harmful to those who eat it…

• Microwaving “excites” water and other food molecules into extremely rapid motion, which produces enough friction to heat the molecules, but also enough friction to deform them
• One study showed that microwaving of breast milk depleted antibodies and prompted breakdown of enzymes
• Another study showed breakdown of vitamin B-12 to inactive degradation products
• Swiss research that compared blood samples from subjects who had eaten microwaved food to blood samples from subjects who had eaten normally prepared food showed that blood hemoglobin levels decreased significantly in the microwave group
• In the same study, white blood cells increased in the microwave group, and LDL cholesterol increased relative to HDL

Let’s go back for a moment to the concept that carotenoids mixed with oil are better absorbed by the body.

A 1997 study showed that microwaving of different types of oils, including virgin olive oil, caused the oils to become degraded. And a 2006 study showed that beta-carotene (the most common carotene, a precursor of vitamin A) was depleted in broccoli steamed in a microwave, compared to broccoli boiled by induction.

So mix carotenoid-depleted broccoli with degraded oil and what do you suppose is the likelihood that you’ll have a wholesome food that still supports immune function and protects your body from DNA damage?

I’m thinking…use the steamer on the stove. Done. That takes care of the vegetable question.

Now…about those popcorn bags.

Long-time readers will recall an e-Alert I sent you three years ago with some unsettling information about what happens inside a popcorn bag that gets microwaved. Those bags are coated with chemicals to prevent the bag from getting soggy during cooking, and those chemicals break down into a substance the Environmental Protection Agency calls a “likely carcinogen.”

And then there’s the butter flavoring. I’ll let alternative health care pioneer William Campbell Douglass II, M.D., break the bad news about that in his Daily Dose titled “Death in a Popcorn Bag.”

Source:
“Get the Most Nutrition From Your Veggies” Allison Aubrey, NPR, 7/27/09, npr.org